Bayesian adaptive designs for drug combinations in early phase clinical trials

Treating patients with combined agents is a growing trend in cancer clinical trials. Evaluating the synergism of multiple drugs is often the primary motivation for such drug-combination studies. Focusing on the drug combination study in the early phase clinical trials, our research is composed of three parts: (1) We conduct a comprehensive comparison of four dose-finding designs in the two-dimensional toxicity probability space and propose using the Bayesian model averaging method to overcome the arbitrariness of the model specification and enhance the robustness of the design; (2) Motivated by a recent drug-combination trial at MD Anderson Cancer Center with a continuous-dose standard of care agent and a discrete-dose investigational agent, we propose a two-stage Bayesian adaptive dose-finding design based on an extended continual reassessment method; (3) By combining phase I and phase II clinical trials, we propose an extension of a single agent dose-finding design. We model the time-to-event toxicity and efficacy to direct dose finding in two-dimensional drug-combination studies. We conduct extensive simulation studies to examine the operating characteristics of the aforementioned designs and demonstrate the designs' good performances in various practical scenarios.^

Bayesian adaptive designs in early phase clinical trials

There are two practical challenges in the phase I clinical trial conduct: lack of transparency to physicians, and the late onset toxicity. In my dissertation, Bayesian approaches are used to address these two problems in clinical trial designs. The proposed simple optimal designs cast the dose finding problem as a decision making process for dose escalation and deescalation. The proposed designs minimize the incorrect decision error rate to find the maximum tolerated dose (MTD). For the late onset toxicity problem, a Bayesian adaptive dose-finding design for drug combination is proposed. The dose-toxicity relationship is modeled using the Finney model. The unobserved delayed toxicity outcomes are treated as missing data and Bayesian data augment is employed to handle the resulting missing data. Extensive simulation studies have been conducted to examine the operating characteristics of the proposed designs and demonstrated the designs' good performances in various practical scenarios.^

S9511: a Southwest Oncology Group phase II study of trimetrexate, 5-fluorouracil, and leucovorin in unresectable or metastatic adenocarcinoma of the stomach.

OBJECTIVE: The primary objective of this trial was to evaluate the response rate for trimetrexate in conjunction with 5-FU and leucovorin (LV) (= TFL) in the treatment of advanced gastric cancer in a phase II, cooperative group setting. METHODS: Patients with locally advanced, unresectable, or metastatic adenocarcinoma of the stomach received trimetrexate 110 mg/m IV over 60 minutes day 1, followed by 5-FU 500 mg/m IV bolus and LV 200 mg/m IV over 60 minutes day 2, followed by oral LV 15 mg every 6 hours x 7 doses, all weekly for 6 weeks followed by 2 weeks of rest, continued until progression. RESULTS: Characteristics for 37 eligible patients: median age 63 (range: 23-83); male/female: 69% of 31%; performance status 0/1/2 15/20/1. The confirmed response rate was 19%, and median overall survival was 6 months. Two patients died as a result of therapy, 1 because of infection without significant neutropenia, and 1 due to perforation of a responding gastric lesion. Seventy-two percent experienced grades 3 and 4 toxicity, most commonly diarrhea, fatigue, and lymphopenia. CONCLUSIONS: This regimen achieves response rates comparable to other 5-FU-based regimens, when used in treatment of incurable gastric cancer. Toxicity appears manageable.

Phase I clinical trials in 56 patients with thyroid cancer: the M. D. Anderson Cancer Center experience.

INTRODUCTION: Thyroid cancer is the most common endocrine malignancy. The outcomes of patients with relapsed thyroid cancer treated on early-phase clinical trials have not been systematically analyzed. PATIENTS AND METHODS: We reviewed the records of consecutive patients with metastatic thyroid cancer referred to the Phase I Clinical Trials Program from March 2006 to April 2008. Best response was assessed by Response Evaluation Criteria in Solid Tumors. RESULTS: Fifty-six patients were identified. The median age was 55 yr (range 35-79 yr). Of 49 patients evaluable for response, nine (18.4%) had a partial response, and 16 (32.7%) had stable disease for 6 months or longer. The median progression-free survival was 1.12 yr. With a median follow-up of 15.6 months, the 1-yr survival rate was 81%. In univariate analysis, factors predicting shorter survival were anaplastic histology (P = 0.0002) and albumin levels less than 3.5 g/dl (P = 0.05). Among 26 patients with tumor decreases, none died (median follow-up 1.3 yr), whereas 52% of patients with any tumor increase died by 1 yr (P = 0.0001). The median time to failure in our phase I clinical trials was 11.5 months vs. 4.1 months for the previous treatment (P = 0.04). CONCLUSION: Patients with advanced thyroid cancer treated on phase I clinical trials had high rates of partial response and prolonged stable disease. Time to failure was significantly longer on the first phase I trial compared with the prior conventional treatment. Patients with any tumor decrease had significantly longer survival than those with any tumor increase.

Optimal, minimax, and Bayesian two-stage designs in two-dose phase II clinical trials

Background: For most cytotoxic and biologic anti-cancer agents, the response rate of the drug is commonly assumed to be non-decreasing with an increasing dose. However, an increasing dose does not always result in an appreciable increase in the response rate. This may especially be true at high doses for a biologic agent. Therefore, in a phase II trial the investigators may be interested in testing the anti-tumor activity of a drug at more than one (often two) doses, instead of only at the maximum tolerated dose (MTD). This way, when the lower dose appears equally effective, this dose can be recommended for further confirmatory testing in a phase III trial under potential long-term toxicity and cost considerations. A common approach to designing such a phase II trial has been to use an independent (e.g., Simon's two-stage) design at each dose ignoring the prior knowledge about the ordering of the response probabilities at the different doses. However, failure to account for this ordering constraint in estimating the response probabilities may result in an inefficient design. In this dissertation, we developed extensions of Simon's optimal and minimax two-stage designs, including both frequentist and Bayesian methods, for two doses that assume ordered response rates between doses. ^ Methods: Optimal and minimax two-stage designs are proposed for phase II clinical trials in settings where the true response rates at two dose levels are ordered. We borrow strength between doses using isotonic regression and control the joint and/or marginal error probabilities. Bayesian two-stage designs are also proposed under a stochastic ordering constraint. ^ Results: Compared to Simon's designs, when controlling the power and type I error at the same levels, the proposed frequentist and Bayesian designs reduce the maximum and expected sample sizes. Most of the proposed designs also increase the probability of early termination when the true response rates are poor. ^ Conclusion: Proposed frequentist and Bayesian designs are superior to Simon's designs in terms of operating characteristics (expected sample size and probability of early termination, when the response rates are poor) Thus, the proposed designs lead to more cost-efficient and ethical trials, and may consequently improve and expedite the drug discovery process. The proposed designs may be extended to designs of multiple group trials and drug combination trials.^

An Innovative Phase I Trial Design Allowing for the Identification of Multiple Potential Maximum Tolerated Doses with Combination Therapy of Targeted Agents

Treatment for cancer often involves combination therapies used both in medical practice and clinical trials. Korn and Simon listed three reasons for the utility of combinations: 1) biochemical synergism, 2) differential susceptibility of tumor cells to different agents, and 3) higher achievable dose intensity by exploiting non-overlapping toxicities to the host. Even if the toxicity profile of each agent of a given combination is known, the toxicity profile of the agents used in combination must be established. Thus, caution is required when designing and evaluating trials with combination therapies. Traditional clinical design is based on the consideration of a single drug. However, a trial of drugs in combination requires a dose-selection procedure that is vastly different than that needed for a single-drug trial. When two drugs are combined in a phase I trial, an important trial objective is to determine the maximum tolerated dose (MTD). The MTD is defined as the dose level below the dose at which two of six patients experience drug-related dose-limiting toxicity (DLT). In phase I trials that combine two agents, more than one MTD generally exists, although all are rarely determined. For example, there may be an MTD that includes high doses of drug A with lower doses of drug B, another one for high doses of drug B with lower doses of drug A, and yet another for intermediate doses of both drugs administered together. With classic phase I trial designs, only one MTD is identified. Our new trial design allows identification of more than one MTD efficiently, within the context of a single protocol. The two drugs combined in our phase I trial are temsirolimus and bevacizumab. Bevacizumab is a monoclonal antibody targeting the vascular endothelial growth factor (VEGF) pathway which is fundamental for tumor growth and metastasis. One mechanism of tumor resistance to antiangiogenic therapy is upregulation of hypoxia inducible factor 1α (HIF-1α) which mediates responses to hypoxic conditions. Temsirolimus has resulted in reduced levels of HIF-1α making this an ideal combination therapy. Dr. Donald Berry developed a trial design schema for evaluating low, intermediate and high dose levels of two drugs given in combination as illustrated in a recently published paper in Biometrics entitled “A Parallel Phase I/II Clinical Trial Design for Combination Therapies.” His trial design utilized cytotoxic chemotherapy. We adapted this design schema by incorporating greater numbers of dose levels for each drug. Additional dose levels are being examined because it has been the experience of phase I trials that targeted agents, when given in combination, are often effective at dosing levels lower than the FDA-approved dose of said drugs. A total of thirteen dose levels including representative high, intermediate and low dose levels of temsirolimus with representative high, intermediate, and low dose levels of bevacizumab will be evaluated. We hypothesize that our new trial design will facilitate identification of more than one MTD, if they exist, efficiently and within the context of a single protocol. Doses gleaned from this approach could potentially allow for a more personalized approach in dose selection from among the MTDs obtained that can be based upon a patient’s specific co-morbid conditions or anticipated toxicities.

Effects of gossypol on DNA replication in mammalian cells

Gossypol, a binaphthalene compound, possesses male infertility effects. However, its mechanism of action and effects on somatic cells are not yet understood. The purpose of this study was to examine the effects of gossypol on mammalian cell growth and DNA replication, using tissue culture cells (HeLa) as an in vivo model.^ Gossypol inhibited DNA synthesis in HeLa cells at low doses, without affecting RNA or protein synthesis. This caused cells to accumulate in S phase without affecting cells in other phases of the cell cycle. The inhibition of DNA synthesis was both dose- and time-dependent. This irreversible block was associated with a decrease in HeLa plating efficiency. Gossypol did bind to DNA but did not measurably affect its ability to serve as a template for DNA polymerase $\alpha$, the major replicative enzyme. Only in the absence of serum could gossypol induce single-strand DNA breaks in HeLa cells; no DNA-DNA or DNA-protein crosslinks were formed.^ Gossypol exhibited dose-dependent inhibition of a number of eukaryotic and prokaryotic replicative DNA polymerases both in vitro and in vivo. This inhibition was kinetically non-competitive with respect to the DNA template and dNTP substrates. Both a filter binding assay and polyacrylamide gel electrophoresis were used to study gossypol binding to DNA polymerase. Inhibition resulted from drug binding to two adjacent amino acid residues on the enzyme. Binding was found to be irreversible and mediated through either non-covalent interactions or by Schiff's base formation between the aldehyde groups of gossypol and the $\varepsilon$-NH$\sb2$ groups of amino acid residues on the polymerase. Structure-function studies using eleven gossypol derivatives revealed that both aldehyde and hydroxyl groups function independently to effect inhibition of DNA polymerase and DNA replication. The activities of DNA polymerase $\beta$ and ribonucleotide reductase were also inhibited by increasing gossypol concentrations.^ These studies demonstrate that the gossypol-mediated inhibition of DNA replication is due in part to inhibition of key replicative enzymes, such as DNA polymerase $\alpha$. The study of DNA polymerase may serve as a model for the interaction of enzymes with gossypol, a drug which may prove useful as a chemotherapeutic agent. ^

Regulation of the expression of {\it mutS, mutL}, and {\it mutH\/} mismatch repair genes in {\it Escherichia coli\/} K-12

Post-replication DNA mismatch repair plays crucial roles in mutation avoidance and maintenance of chromosome stability in both prokaryotes and eukaryotes. In humans, deficiency in this repair system leads to a predisposition for certain cancers. The biochemistry of this repair system has been best studied in a model bacterium Escherichia coli. In this thesis, regulation of expression of mutS, mutL and mutH genes, whose products mediate methyl-directed mismatch (MDM) repair in E. coli, is investigated. One-step affinity purification schemes were developed to purify E. coli MutS, MutL and MutH proteins fused to a His-6-affinity tag. His-6-MutS exhibited the same mismatch binding activity and specificity as the native MutS protein. Purified His-6-MutS, -MutL and -MutH proteins were used to develop quantitative Western blotting assays for amounts of MutS, MuL and MutH proteins under various conditions. It was found that the three proteins were present in relatively low amounts in exponentially growing cells and MutS and MutH were diminished in stationary-phase cells. Further studies indicated that the drop in the amounts of MutS and MutH proteins in stationary-phase cells was mediated through RpoS, a key global regulator of stationary-phase transition. In both exponential- and stationary-phase cells, MutS amount was also negatively regulated by the Hfq (HF-I) global regulator, which is required for RpoS translation, through an RpoS-independent mechanism. $\beta$-galactosidase assays of mutS-lacZ operon and gene fusions suggested that hfq regulates mutS posttranscriptionally, and RNase T2 protection assays revealed that Hfq destabilizes mutS transcripts in exponentially growing cells. To study the relation between regulation of MDM repair and mutagenesis, amounts of MutS, MutL and MutH were measured in starved cells undergoing adaptive mutagenesis. It was found that MutS amount dropped drastically, MutH amount dropped slightly, whereas MutL amount remained essentially constant in starved cells. Overexpression of MutL did not reverse the drop in the amounts of MutS or MutH protein. These results ruled out several explanations for a phenomenon in which overexpression of MutL, but not MutS, reversed adaptive mutagenesis. The findings further suggested that functional MutL is limiting during adaptive mutagenesis. The implications of regulation of the MDM repair are discussed in the context of mutagenesis, pathogenesis and tumorigenesis. ^

Immune restoration of patients with chronic myelogenous leukemia in complete cytogenetic remission

Imatinib mesylate (IM) and Interferon-alfa (IFN-α) are currently the two most efficacious therapies for patients with chronic myelogenous leukemia (CML). IFN-α induces durable complete cytogentic remission (CCR) in about 25% of CML patients whereas IM, a tyrosine kinase inhibitor, induces CCR in 50% of patients who are resistant to IFN-α and in 75% of patients in early chronic phase of CML. However, the detection of minimal residual disease without clinical relapse suggests that host immune surveillance plays a very important role in controlling the progression of disease. ^ T lymphocytes and dendritic cells (DC) are the two most crucial players in the immune system. In my study, we focused on the effects of treatment with either IM or IFN-α on the functions of both DC and T cells, as exemplified by the ability of DC to present antigen to T cells and activated T cells to synthesize cytokines. Our studies show that cytokine production by T cells activated through the T-cell receptor (TCR) was significantly lower in CML patients treated with IM, but not with IFN-α, when compared with activated T cells of control subjects. Suppression of T cell function by IM albeit transient and reversible, was through the downregulation of the phosphorylation of Zap-70, Lck, and LAT. ^ Our data also show that the myeloid DC (DC1) and the plasmacytoid DC (DC2) are lower in chronic phase CML. Whereas neither therapy restored the level of DC2 to normal levels, the number of DC1 was normalized by either therapy. However, only IFN-α, and not IM, restored DC2 function to normal, as exemplified by the production of IFN-α in response to exposure to live influenza virus. Moreover, in vitro differentiation and maturation of DC1 from monocyte precursors in patients receiving either therapy was not normal and was reflected in their ability to present antigen to autologous T cells. ^ In summary, we report that there are differences in immune responses of CML patients treated with IM or IFN-α that may be the result of long-term effects on the host immune system by the individual therapy. ^

The role of deregulated E2F1 expression in brain tumors

Mutations disabling the retinoblastoma (Rb) pathway are among the most common in human cancers, including brain cancer. These mutations promote tumor development through deregulated control of the E2F family of transcription factors. E2F1 belongs to a class of E2F's identified as transcriptional activators and involved in the G1/S phase transition of the cell. However, E2F-1 presents with a paradox as it is considered to have membership in two gene classes, functioning as both an oncogene and a tumor suppressor. This unusual trait generates a degree of uncertainty on the role that E2F1 plays in the development or maintenance of any given tumor. Here we show that E2F1 functions as an oncogene in brain tumors through the generation of mice engineered to overexpress E2F1 specifically within glial cells and neuronal progenitors as directed by the GFAP promoter. Mice carrying the transgene develop with high penetrance a phenotype characterized by neurological deficits including paresia, ataxia, head tilt and seizures. MRI imagining of the tgE2F1 mice reveals a low incidence of mild hydrocephalus, and most notably, histological analysis demonstrates that 25% of tgE2F1 mice present with the spontaneous formation of malignant brain tumors. Overall these neoplasms show histological features from a wide range of aggressive brain cancers including medulloblastoma, choroid plexus carcinoma, primary neuroectodermic tumor and malignant gliomas. Isolation and characterization of astrocytes from the tgE2F1 animal reveals a highly proliferative population of cells with 55% ± 2.5 of the tgE2F1astrocytes, 35% ± 3.4 normal mouse astrocytes in S-phase and the acquired capacity to grow in anchorage independent conditions. Additionally tgE2F1 astrocytes show an aberrant phenotype with random chromosomal fusions and nearly all cells demonstrating polyploidy. Taken together, this model forces a comparison to human brain tumor formation. Mouse age as related to tumoral mimics the human scenario with juvenile tgE2F1 mice presenting embryonal tumors typically identified in children, and older tgE2F1 mice demonstrating gliomas. In this regard, this study suggests a global role for E2F1 in the formation and maintenance of multilineage brain tumors, irrefutably establishing E2F1 as an oncogene in the brain. ^

The role of SRC family kinase activation in prostate cancer growth and lymph node metastasis

Aberrant expression and/or activation of Src Family of non-receptor protein tyrosine kinases (SFKs) occur frequently during progressive stages of multiple types of human malignancies, including prostate cancer. Two SFKs, Src and Lyn, are expressed and implicated in prostate cancer progression. Work in this dissertation investigated the specific roles of Src and Lyn in the prostate tumor progression, and the effects of SFK inhibition on prostate tumor growth and lymph node metastasis in pre-clinical mouse models. ^ Firstly, using a pharmacological inhibitor of SFKs in clinical trials, dasatinib, I demonstrated that SFK inhibition affects both cellular migration and proliferation in vitro. Systemic administration of dasatinib reduced primary tumor growth, as well as development of lymph node metastases, in both androgen-sensitive and -resistant orthotopic prostate cancer mouse models. Immunohistochemical analysis of the primary tumors revealed that dasatinib treatment decreased SFK phosphorylation but not expression, resulting in decreased cellular proliferation and increased apoptosis. For this analysis of immunohistochemical stained tissues, I developed a novel method of quantifying immunohistochemical stain intensity that greatly reduced the inherent bias in analyzing staining intensity. ^ To determine if Src and Lyn played overlapping or distinct roles in prostate cancer tumor growth and progression, Src expression alone was inhibited by small-interfering RNA. The resulting stable cell lines were decreased in migration, but not substantially affected in proliferation rates. In contrast, an analogous strategy targeting Lyn led to stable cell lines in which proliferation rates were significantly reduced. ^ Lastly, I tested the efficacy of a novel SFK inhibitor (KX2-391) targeting peptide substrate-binding domain, on prostate cancer growth and lymph node metastasis in vivo. I demonstrated that KX2-391 has similar effects as dasatinib, an ATP-competitive small molecular inhibitor, on both the primary tumor growth and development of lymph node metastasis in vivo, work that contributed to the first-in-man Phase I clinical trial of KX2-391. ^ In summary, studies in this dissertation provide the first demonstration that Src and Lyn activities affect different cellular functions required for prostate tumor growth and metastasis, and SFK inhibitors effectively reduce primary tumor growth and lymph node metastasis. Therefore, I conclude that SFKs are promising therapeutic targets for treatment of human prostate cancer. ^

AN ASSESSMENT OF AFLATOXIN B1, AND OTHER SELECTED VARIABLES, IN A RURAL ENVIRONMENT AND ASSOCIATED CANCER RISK (TEXAS)

A study to assess possible exposure to carcinogenic metabolites (aflatoxins) from a mold Aspergillus flavus has been made in a rice producing area of Brazoria County, Texas. One hundred samples of unmilled rice were analyzed by thin-layer chromatography (TLC) for the amount of aflatoxin produced by the mold during rice growth and storage. Two well water samples and two rice elevator dust samples were also checked for possible aflatoxin content. The mortality rates from gastrointestinal and urinary tract cancers in the rice-growing part of the county were compared with mortality rates in the nonrice-producing areas of the same county.^ This study was an outgrowth of an earlier investigation by Cech and co-workers in Brazoria County which focused on environmental differences, specifically on the quality of drinking water in the former residences of decedents from primary liver cancer. It also compared subjects who died from other causes. The author of this dissertation participated in this phase of the overall investigation by performing some of the chemical analyses and by preparing synographic maps of water quality, and thus, part of those results from the early phase is also included in this manuscript.^ No aflatoxin was detected by TLC methods. However, when extracts of rice dust were checked for mutagenesis by the Ames Salmonella-microsome assay as a supplement to the TLC analysis, the result suggested that these dusts might have contained mutagenic material. The age-adjusted mortality rates in the rice-growing area were higher than those in the comparison area for both male and female gastrointestinal tract cancer and for male urinary tract cancer, but the differences were not statistically significant. ^

A simulation study using the hybrid statistic and the meta-analysis t-test for data with matched and unmatched subjects in the interim analysis of clinical trials

An interim analysis is usually applied in later phase II or phase III trials to find convincing evidence of a significant treatment difference that may lead to trial termination at an earlier point than planned at the beginning. This can result in the saving of patient resources and shortening of drug development and approval time. In addition, ethics and economics are also the reasons to stop a trial earlier. In clinical trials of eyes, ears, knees, arms, kidneys, lungs, and other clustered treatments, data may include distribution-free random variables with matched and unmatched subjects in one study. It is important to properly include both subjects in the interim and the final analyses so that the maximum efficiency of statistical and clinical inferences can be obtained at different stages of the trials. So far, no publication has applied a statistical method for distribution-free data with matched and unmatched subjects in the interim analysis of clinical trials. In this simulation study, the hybrid statistic was used to estimate the empirical powers and the empirical type I errors among the simulated datasets with different sample sizes, different effect sizes, different correlation coefficients for matched pairs, and different data distributions, respectively, in the interim and final analysis with 4 different group sequential methods. Empirical powers and empirical type I errors were also compared to those estimated by using the meta-analysis t-test among the same simulated datasets. Results from this simulation study show that, compared to the meta-analysis t-test commonly used for data with normally distributed observations, the hybrid statistic has a greater power for data observed from normally, log-normally, and multinomially distributed random variables with matched and unmatched subjects and with outliers. Powers rose with the increase in sample size, effect size, and correlation coefficient for the matched pairs. In addition, lower type I errors were observed estimated by using the hybrid statistic, which indicates that this test is also conservative for data with outliers in the interim analysis of clinical trials.^

CHARACTERIZATION OF DIFFERENTIATION AND PROGNOSTIC BIOMARKERS ON CD8+ TUMOR-INFILTRATING LYMPHOCYTES IN METASTATIC MELANOMA

CD8+ cytotoxic T lymphocytes (CTL) frequently infiltrate tumors, yet most melanoma patients fail to undergo tumor regression. We studied the differentiation of the CD8+ tumor-infiltrating lymphocytes (TIL) from 44 metastatic melanoma patients using known T-cell differentiation markers. We also compared CD8+ TIL against the T cells from matched melanoma patients’ peripheral blood. We discovered a novel subset of CD8+ TIL co-expressing early-differentiation markers, CD27, CD28, and a late/senescent CTL differentiation marker, CD57. This CD8+CD57+ TIL expressed a cytolytic enzyme, granzyme B (GB), yet did not express another cytolytic pore-forming molecule, perforin (Perf). In contrast, the CD8+CD57+ T cells in the periphery were CD27-CD28-, and GBHi and PerfHi. We found this TIL subset was not senescent and could be induced to proliferate and differentiate into CD27-CD57+, perforinHi, mature CTL. This further differentiation was arrested by TGF-β1, an immunosuppressive cytokine known to be produced by many different kinds of tumors. Therefore, we have identified a novel subset of incompletely differentiated CD8+ TIL that resembled those found in patients with uncontrolled chronic viral infections. In a related study, we explored prognostic biomarkers in metastatic melanoma patients treated in a Phase II Adoptive Cell Therapy (ACT) trial, in which autologous TIL were expanded ex vivo with IL-2 and infused into lymphodepleted patients. We unexpectedly found a significant positive clinical association with the infused CD8+ TIL expressing B- and T- lymphocyte attentuator (BTLA), an inhibitory T-cell receptor. We found that CD8+BTLA+ TIL had a superior proliferative response to IL-2, and were more capable of autocrine IL-2 production in response to TCR stimulation compared to the CD8+BTLA- TIL. The CD8+BTLA+ TIL were less differentiated and resembled the incompletely differentiated CD8+ TIL described above. In contrast, CD8+BTLA- TIL were poorly proliferative, expressed CD45RA and killer-cell immunoglobulin-like receptors (KIRs), and exhibited a gene expression signature of T cell deletion. Surprisingly, ligation of BTLA by its cognate receptor, HVEM, enhanced the survival of CD8+BTLA+ TIL by activating Akt/PKB. Our studies provide a comprehensive characterization of CD8+ TIL differentiation in melanoma, and revealed BTLA as a novel T-cell differentiation marker along with its role in promoting T cell survival.

Implication of bFGF signaling in lung carcinogenesis

A Western Array Screening system in conjunction with an in vitro lung carcinogenesis model, which consists of human bronchial epithelial (HBE) cells representing normal (NHBE), immortalized (BEAS-2B and 1799), transformed (1198), and tumorigenic (1170-I) was used to test the hypothesis that lung carcinogenesis involves specific changes in signaling proteins. Forty six proteins whose expression was upregulated by >2 fold and 23 proteins whose expression was downregulated by >2 fold in 1170-I compared to NHBE cells were identified. The levels of six proteins including bFGF (both intracellular and secreted), Akt and p70s6K in the PI3KJp70s6K pathway and the bFGF receptor (FGFR1) were upregulated in different stages of lung carcinogenesis. Akt activity and phospho-p70s6K were also increased in 1170-I compared to NHBE cells, suggesting that PI3K/p70s6K pathway is activated during lung carcinogenesis. bFGF treatment stimulated the growth of the 1170-I cells. Both tyrosine phosphorylation of FGFR1 and cell growth were inhibited in 1170-I cells after overexpression of dominant-negative(DN) FGFR1. Growth inhibition involved a G2 arrest related to decreased cdc2 activity, cdc25C downregulation, Wee1, p21(WAF1) and p27(Kip1) upregulation. Apoptosis was observed in tumorigenic but not in normal cells after overexpression of DNFGFR1. Confluent NHBE cells, were much less sensitive to the growth inhibition by DNFGFR1 compared to other cell lines analyzed. bFGF increased phospho-Akt and phospho-p70s6K in 1170-I cells. The Akt inhibitor LY294002 and the p70s6K inhibitor rapamycin inhibited bFGF-stimulated cell growth in 1170-I cells. Both agents downregulated the bFGF-induced increase in S phase by inducing G1 arrest. Also, LY294002 inhibited bFGF increased phospho-Akt, while both LY294002 and rapamycin inhibited bFGF increased phospho-p70s6K. Thus, cell proliferation stimulated by bFGF in 1170-I cells was at least partially mediated by PI3K/p70s6K pathway. Hsp90 was upregulated by bFGF in 1170-I cells. Its inhibitor geldanamycin inhibited the bFGF-stimulated growth via inducing apoptosis and G2 arrest through decreases in cdc2 expression/activity and p21 upregulation, and decreased Akt/phospho-Akt, p70s6K/phospho-p70s6K and Bad. Hsp90, p70s6K and Bad were found in the same complex, which may be important for signaling cell survival. Taken together, our study suggests that bFGF signaling, especially PI3K/p70s6K pathway, is important for lung carcinogenesis. ^