Prevalence of germ-line mutations in p16, p19ARF, and CDK4 in familial melanoma:analysis of a clinic-based population

Five to ten percent of individuals with melanoma have another affected family member, suggesting familial predisposition. Germ-line mutations in the cyclin-dependent kinase (CDK) inhibitor p16 have been reported in a subset of melanoma pedigrees, but their prevalence is unknown in more common cases of familial melanoma that do not involve large families with multiple affected members. We screened for germ-line mutations in p16 and in two other candidate melanoma genes, p19ARF and CDK4, in 33 consecutive patients treated for melanoma; these patients had at least one affected first or second degree relative (28 independent families). Five independent, definitive p16 mutations were detected (18%, 95% confidence interval: 6%, 37%), including one nonsense, one disease-associated missense, and three small deletions. No mutations were detected in CDK4. Disease-associated mutations in p19ARF, whose transcript is derived in part from an alternative codon reading frame of p16, were only detected in patients who also had mutations inactivating p16. We conclude that germ-line p16 mutations are present in a significant fraction of individuals who have melanoma and a positive family history.

STI-571 (imatinib mesylate) enhances the apoptotic efficacy of pyrrolo-1,5-benzoxazepine-6, a novel microtubule-targeting agent, in both STI-571-sensitive and -resistant Bcr-Abl-positive human chronic myeloid leukemia cells

Interactions between the Bcr-Abl kinase inhibitor STI-571 (imatinib mesylate) and a novel microtubule-targeting agent (MTA), pyrrolo-1,5-benzoxazepine (PBOX)-6, were investigated in STI-571-sensitive and -resistant human chronic myeloid leukemia (CML) cells. Cotreatment of PBOX-6 with STI-571 induced significantly more apoptosis in Bcr-Abl-positive CML cell lines (K562 and LAMA-84) than either drug alone (P < 0.01). Cell cycle analysis of propidium iodide-stained cells showed that STI-571 significantly reduced PBOX-6-induced G2M arrest and polyploid formation with a concomitant increase in apoptosis. Similar results were obtained in K562 CML cells using lead MTAs (paclitaxel and nocodazole) in combination with STI-571. Potentiation of PBOX-6-induced apoptosis by STI-571 was specific to Bcr-Abl-positive leukemia cells with no cytoxic effects observed on normal peripheral blood cells. The combined treatment of STI-571 and PBOX-6 was associated with the down-regulation of Bcr-Abl and repression of proteins involved in Bcr-Abl transformation, namely the antiapoptotic proteins Bcl-x(L) and Mcl-1. Importantly, PBOX-6/STI-571 combinations were also effective in STI-571-resistant cells. Together, these findings highlight the potential clinical benefits in simultaneously targeting the microtubules and the Bcr-Abl oncoprotein in STI-571-sensitive and -resistant CML cells.

Expression of the NF-kappaB targets BCL2 and BIRC5/Survivin characterizes small B-cell and aggressive B-cell lymphomas, respectively

Nuclear factor kappa B (NF-kappaB) activation has been proposed as a cardinal feature of tumourigenesis, although the precise mechanism, frequency, relevance, and extent of NF-kappaB activation in lymphomas remain to be fully elucidated. In this study, expression profiling and tissue microarray studies of 209 and 323 non-Hodgkin's lymphomas (NHLs) respectively, including the most frequent sub-types of NHL, were employed to generate a hypothesis concerning the most common NF-kappaB targets in NHL. These analyses showed that NF-kappaB activation is a common phenomenon in NHL, resulting in the expression of distinct sets of NF-kappaB target genes, depending on the cell context. BCL2 and BIRC5/Survivin were identified as key NF-kappaB targets and their expression distinguished small and aggressive B-cell lymphomas, respectively. Interestingly, in the vast majority of B-cell lymphomas, the expression of these markers was mutually exclusive. A set of genes was identified whose expression correlates either with BIRC5/Survivin or with BCL2. BIRC5/Survivin expression, in contrast to BCL2, was associated with a signature of cell proliferation (overexpression of cell cycle control, DNA repair, and polymerase genes), which may contribute to the aggressive phenotype and poor prognosis of these lymphomas. Strikingly, mantle cell lymphoma and chronic lymphocytic leukaemia expressed highly elevated levels of BCL2 protein and mRNA, higher than that observed in reactive mantle zone cells or even in follicular lymphomas, where BCL2 expression is deregulated through the t(14;18) translocation. In parallel with this observation, BIRC5/Survivin expression was higher in Burkitt's lymphoma and diffuse large B-cell lymphoma than in non-tumoural germinal centre cells. In vitro studies confirmed that NF-kappaB activation contributes to the expression of both markers. In cell lines representing aggressive lymphomas, NF-kappaB inhibition resulted in a decrease in BIRC5/Survivin expression. Meanwhile, in chronic lymphocytic leukaemia (CLL)-derived lymphocytes, NF-kappaB inhibition resulted in a marked decrease in BCL2 expression.

Selective induction of apoptosis by the pyrrolo-1,5-benzoxazepine 7-[[dimethylcarbamoyl]oxy]-6-(2-naphthyl)pyrrolo-[2,1-d] (1,5)-benzoxazepine (PBOX-6) in Leukemia cells occurs via the c-Jun NH2-terminal kinase-dependent phosphorylation and inactivation of Bcl-2 and Bcl-XL

Overexpression of the Bcl-2 proto-oncogene in tumor cells confers resistance against chemotherapeutic drugs. In this study, we describe how the novel pyrrolo-1,5-benzoxazepine compound 7-[[dimethylcarbamoyl]oxy]-6-(2-naphthyl)pyrrolo-[2,1-d] (1,5)-benzoxazepine (PBOX-6) selectively induces apoptosis in Bcl-2-overexpressing cancer cells, whereas it shows no cytotoxic effect on normal peripheral blood mononuclear cells. PBOX-6 overcomes Bcl-2-mediated resistance to apoptosis in chronic myelogenous leukemia (CML) K562 cells by the time- and dose-dependent phosphorylation and inactivation of antiapoptotic Bcl-2 family members Bcl-2 and Bcl-XL. PBOX-6 also induces Bcl-2 phosphorylation and apoptosis in wild-type T leukemia CEM cells and cells overexpressing Bcl-2. This is in contrast to chemotherapeutic agents such as etoposide, actinomycin D, and ultraviolet irradiation, whereby overexpression of Bcl-2 confers resistance against apoptosis. In addition, PBOX-6 induces Bcl-2 phosphorylation and apoptosis in wild-type Jurkat acute lymphoblastic leukemia cells and cells overexpressing Bcl-2. However, Jurkat cells containing a Bcl-2 triple mutant, whereby the principal Bcl-2 phosphorylation sites are mutated to alanine, demonstrate resistance against Bcl-2 phosphorylation and apoptosis. PBOX-6 also induces the early and transient activation of c-Jun NH2-terminal kinase (JNK) in CEM cells. Inhibition of JNK activity prevents Bcl-2 phosphorylation and apoptosis, implicating JNK in the upstream signaling pathway leading to Bcl-2 phosphorylation. Collectively, these findings identify Bcl-2 phosphorylation and inactivation as a critical step in the apoptotic pathway induced by PBOX-6 and highlight its potential as an effective antileukemic agent.

Activation of the c-Jun N-terminal kinase (JNK) signaling pathway is essential during PBOX-6-induced apoptosis in chronic myelogenous leukemia (CML) cells

The mitogen-activated protein (MAP) kinase family is activated in response to a wide variety of external stress signals such as UV irradiation, heat shock, and many chemotherapeutic drugs and leads to the induction of apoptosis. A novel series of pyrrolo-1,5-benzoxazepines have been shown to potently induce apoptosis in chronic myelogenous leukemia (CML) cells, which are resistant to many chemotherapeutic agents. In this study we have delineated part of the mechanism by which a representative compound known as PBOX-6 induces apoptosis. We have investigated whether PBOX-6 induces activation of MAP kinase signaling pathways in CML cells. Treatment of K562 cells with PBOX-6 resulted in the transient activation of two JNK isoforms, JNK1 and JNK2. In contrast, PBOX-6 did not activate the extracellular signal-regulated kinase (ERK) or p38. Apoptosis was found to occur independently of the small GTPases Ras, Rac, and Cdc42 but involved phosphorylation of the JNK substrates, c-Jun and ATF-2. Pretreatment of K562 cells with the JNK inhibitor, dicoumarol, abolished PBOX-6-induced phosphorylation of c-Jun and ATF-2 and inhibited the induced apoptosis, suggesting that JNK activation is an essential component of the apoptotic pathway induced by PBOX-6. Consistent with this finding, transfection of K562 cells with the JNK scaffold protein, JIP-1, inhibited JNK activity and apoptosis induced by PBOX-6. JIP-1 specifically scaffolds JNK, MKK7, and members of the mixed-lineage kinase (MLK) family, implicating these kinases upstream of JNK in the apoptotic pathway induced by PBOX-6 in K562 cells.

Abl expression, tumour grade, and apoptosis in chondrosarcoma

AIMS: To determine whether Abl immunoreactivity correlates with grade and cell kinetics (apoptosis and mitosis) in chondrosarcoma.

METHODS: Sections from 16 chondrosarcomas were stained immunohistochemically using a polyclonal antibody to the c-Abl/Bcr-Abl oncoprotein. Apoptotic indices and mitotic indices were assessed in all tumours. Sections from 24 paraffin wax blocks of human fetal rib (gestational ages, 15-42 weeks) were also stained to determine whether the Abl protein is synthesised consistently throughout endochondral ossification.

RESULTS: Abl staining in immature fetal rib chondrocytes at all stages of development was predominantly nuclear, and 70% of cells showed moderate to strong staining. Abl immunoreactivity was minimal or absent in hypertrophic chondrocytes about to undergo apoptosis at the growth plate. There was strong Abl staining in grade 1 and grade 2 chondrosarcomas but staining was greatly reduced or absent in grade 3 chondrosarcomas. There was a very significant linear correlation between apoptotic index (mean, 0.68%; range, 0-3.2%) and mitotic index (mean, 0.23%; range, 0-0.9%), and both indices were significantly lower in grade 1 than in grade 2 and grade 3 chondrosarcomas.

CONCLUSIONS: These data suggest that abl gene expression is associated with differentiation and apoptosis inhibition in fetal and neoplastic chondrocytes. However, these putative effects cannot be ascribed solely to the Abl protein, because several additional factors contribute to the regulation of both differentiation and apoptosis.

Sorting out mix-ups. The provenance of tissue sections may be confirmed by PCR using microsatellite markers

Standard identification systems usually ensure that biopsy material is correctly associated with a given patient. Sometimes, as when a tumor is unexpectedly found, the provenance (proof of origin) of a tissue sample may be questioned; the tissue may have been mislabelled or contaminated with tissue from another patient. Techniques used to confirm tissue provenance include comparing either tissue markers of gender or ABO blood groups; however, these methods have weak confirmatory power. Recently, the use of DNA-based polymerase chain reaction (PCR) techniques has been reported. Paired, formalin-fixed, paraffin-embedded, 10 microns tissue sections were selected from 17 patients, 8 of whom had carcinoma, either by dividing a biopsy section, using sequential biopsies, or sequential biopsy and autopsy tissue. The resulting 36 samples were coded before analysis. In two additional cases, 1-mm fragments of tumor from one patient were included in the tissue block of benign tissue from another patient, the tumor fragments were identified on hematoxylin-and-eosin-stained sections, separately scraped off the glass slide, and analyzed. Tissue from two clinical cases, one of suspected mislabelling and one with a suspected carry-over of malignant tissue were also investigated. Short tandem repeat sequences (STR) or microsatellites, are 2-5 base pair repeats that vary in their repeat number between individuals. This variation (polymorphism) can be assessed using a PCR. A panel of markers of 3 STRs; ACPP, INT 2, and CYP 19 (on chromosomes 3, 11, and 15, respectively) were used. DNA was isolated from the samples after xylene deparaffinization and proteinase digestion, and was then amplified in a radioactive PCR using primers selected to give a product size ranging from 136-178 bases. Amplified products were electrophoresed on denaturing polyacrylamide gels, dried, and autoradiographed. DNA segments were successfully extracted from all samples but one, which was fixed in Bouin's fluid. By comparing allele sizes from the panel, all tissue pairs (other than the Bouin's pair) were successfully matched, the 1-mm tumor fragments were correctly assigned, and the two clinical problems were solved. STRs are highly informative and robust markers, well suited to PCR of small portions of tissue sections, and are an effective method to confirm the provenance of benign and malignant biopsy and autopsy material.

O-GlcNAc transferase integrates metabolic pathways to regulate the stability of c-MYC in human prostate cancer cells

Metabolic disruptions that occur widely in cancers offer an attractive focus for generalized treatment strategies. The hexosamine biosynthetic pathway (HBP) senses metabolic status and produces an essential substrate for O-linked β-N-acetylglucosamine transferase (OGT), which glycosylates and thereby modulates the function of its target proteins. Here, we report that the HBP is activated in prostate cancer cells and that OGT is a central regulator of c-Myc stability in this setting. HBP genes were overexpressed in human prostate cancers and androgen regulated in cultured human cancer cell lines. Immunohistochemical analysis of human specimens (n = 1987) established that OGT is upregulated at the protein level and that its expression correlates with high Gleason score, pT and pN stages, and biochemical recurrence. RNA interference-mediated siliencing or pharmacologic inhibition of OGT was sufficient to decrease prostate cancer cell growth. Microarray profiling showed that the principal effects of OGT inhibition in prostate cancer cells were related to cell-cycle progression and DNA replication. In particular, c-MYC was identified as a candidate upstream regulator of OGT target genes and OGT inhibition elicited a dose-dependent decrease in the levels of c-MYC protein but not c-MYC mRNA in cell lines. Supporting this relationship, expression of c-MYC and OGT was tightly correlated in human prostate cancer samples (n = 1306). Our findings identify HBP as a modulator of prostate cancer growth and c-MYC as a key target of OGT function in prostate cancer cells.

ER stress-mediated autophagy promotes Myc-dependent transformation and tumor growth

The proto-oncogene c-Myc paradoxically activates both proliferation and apoptosis. In the pathogenic state, c-Myc-induced apoptosis is bypassed via a critical, yet poorly understood escape mechanism that promotes cellular transformation and tumorigenesis. The accumulation of unfolded proteins in the ER initiates a cellular stress program termed the unfolded protein response (UPR) to support cell survival. Analysis of spontaneous mouse and human lymphomas demonstrated significantly higher levels of UPR activation compared with normal tissues. Using multiple genetic models, we demonstrated that c-Myc and N-Myc activated the PERK/eIF2α/ATF4 arm of the UPR, leading to increased cell survival via the induction of cytoprotective autophagy. Inhibition of PERK significantly reduced Myc-induced autophagy, colony formation, and tumor formation. Moreover, pharmacologic or genetic inhibition of autophagy resulted in increased Myc-dependent apoptosis. Mechanistically, we demonstrated an important link between Myc-dependent increases in protein synthesis and UPR activation. Specifically, by employing a mouse minute (L24+/-) mutant, which resulted in wild-type levels of protein synthesis and attenuation of Myc-induced lymphomagenesis, we showed that Myc-induced UPR activation was reversed. Our findings establish a role for UPR as an enhancer of c-Myc-induced transformation and suggest that UPR inhibition may be particularly effective against malignancies characterized by c-Myc overexpression.

Molecular subtyping of primary prostate cancer reveals specific and shared target genes of different ETS rearrangements

This work aimed to evaluate whether ETS transcription factors frequently involved in rearrangements in prostate carcinomas (PCa), namely ERG and ETV1, regulate specific or shared target genes. We performed differential expression analysis on nine normal prostate tissues and 50 PCa enriched for different ETS rearrangements using exon-level expression microarrays, followed by in vitro validation using cell line models. We found specific deregulation of 57 genes in ERG-positive PCa and 15 genes in ETV1-positive PCa, whereas deregulation of 27 genes was shared in both tumor subtypes. We further showed that the expression of seven tumor-associated ERG target genes (PLA1A, CACNA1D, ATP8A2, HLA-DMB, PDE3B, TDRD1, and TMBIM1) and two tumor-associated ETV1 target genes (FKBP10 and GLYATL2) was significantly affected by specific ETS silencing in VCaP and LNCaP cell line models, respectively, whereas the expression of three candidate ERG and ETV1 shared targets (GRPR, KCNH8, and TMEM45B) was significantly affected by silencing of either ETS. Interestingly, we demonstrate that the expression of TDRD1, the topmost overexpressed gene of our list of ERG-specific candidate targets, is inversely correlated with the methylation levels of a CpG island found at -66 bp of the transcription start site in PCa and that TDRD1 expression is regulated by direct binding of ERG to the CpG island in VCaP cells. We conclude that ETS transcription factors regulate specific and shared target genes and that TDRD1, FKBP10, and GRPR are promising therapeutic targets and can serve as diagnostic markers for molecular subtypes of PCa harboring specific fusion gene rearrangements.

Selecting the best targeted agent in first-line treatment of unresectable liver metastases from colorectal cancer:does the bench have the answers?

For physicians facing patients with organ-limited metastases from colorectal cancer, tumor shrinkage and sterilization of micrometastatic disease is the main goal, giving the opportunity for secondary surgical resection. At the same time, for the majority of patients who will not achieve a sufficient tumor response, disease control remains the predominant objective. Since FOLFOX or FOLFIRI have similar efficacies, the challenge is to define which could be the most effective targeted agent (anti-EGFR or anti-VEGF) to reach these goals. Therefore, a priori molecular identification of patients that could benefit from anti-EGFR or anti-VEGF monoclonal antibodies (i.e. the currently approved targeted therapies for metastatic colorectal cancer) is of critical importance. In this setting, the KRAS mutation status was the first identified predictive marker of response to anti-EGFR therapy. Since it has been demonstrated that tumors with KRAS mutation do not respond to anti-EGFR therapy, KRAS status must be determined prior to treatment. Thus, for KRAS wild-type patients, the choices that remain are either anti-VEGF or anti-EGFR. In this review, we present the most updated data from translational research programs dealing with the identification of biomarkers for response to targeted therapies.

EGF61 polymorphism predicts complete pathologic response to cetuximab-based chemoradiation independent of KRAS status in locally advanced rectal cancer patients

BACKGROUND: Cetuximab has shown significant clinical activity in metastatic colon cancer. However, cetuximab-containing neoadjuvant chemoradiation has not been shown to improve tumor response in locally advanced rectal cancer patients in recent phase I/II trials. We evaluated functional germline polymorphisms of genes involved in epidermal growth factor receptor pathway, angiogenesis, antibody-dependent cell-mediated cytotoxicity, DNA repair, and drug metabolism, for their potential role as molecular predictors for clinical outcome in locally advanced rectal cancer patients treated with preoperative cetuximab-based chemoradiation.

METHODS: 130 patients (74 men and 56 women) with locally advanced rectal cancer (4 with stage II, 109 with stage III, and 15 with stage IV, 2 unknown) who were enrolled in phase I/II clinical trials treated with cetuximab-based chemoradiation in European cancer centers were included. Genomic DNA was extracted from formalin-fixed paraffin-embedded tumor samples and genotyping was done by using PCR-RFLP assays. Fisher's exact test was used to examine associations between polymorphisms and complete pathologic response (pCR) that was determined by a modified Dworak classification system (grade III vs. grade IV: complete response).

RESULTS: Patients with the epidermal growth factor (EGF) 61 G/G genotype had pCR of 45% (5/11), compared with 21% (11/53) in patients heterozygous, and 2% (1/54) in patients homozygous for the A/A allele (P < 0.001). In addition, this association between EGF 61 G allele and pCR remained significant (P = 0.019) in the 59 patients with wild-type KRAS.

CONCLUSION: This study suggested EGF A+61G polymorphism to be a predictive marker for pCR, independent of KRAS mutation status, to cetuximab-based neoadjuvant chemoradiation of patients with locally advanced rectal cancer.

Tumor suppressor Ras-association domain family 1 isoform A is a novel regulator of cardiac hypertrophy

BACKGROUND: Ras signaling regulates a number of important processes in the heart, including cell growth and hypertrophy. Although it is known that defective Ras signaling is associated with Noonan, Costello, and other syndromes that are characterized by tumor formation and cardiac hypertrophy, little is known about factors that may control it. Here we investigate the role of Ras effector Ras-association domain family 1 isoform A (RASSF1A) in regulating myocardial hypertrophy.

METHODS AND RESULTS: A significant downregulation of RASSF1A expression was observed in hypertrophic mouse hearts, as well as in failing human hearts. To further investigate the role of RASSF1A in cardiac (patho)physiology, we used RASSF1A knock-out (RASSF1A(-)(/)(-)) mice and neonatal rat cardiomyocytes with adenoviral overexpression of RASSF1A. Ablation of RASSF1A in mice significantly enhanced the hypertrophic response to transverse aortic constriction (64.2% increase in heart weight/body weight ratio in RASSF1A(-)(/)(-) mice compared with 32.4% in wild type). Consistent with the in vivo data, overexpression of RASSF1A in cardiomyocytes markedly reduced the cellular hypertrophic response to phenylephrine stimulation. Analysis of molecular signaling events in isolated cardiomyocytes indicated that RASSF1A inhibited extracellular regulated kinase 1/2 activation, likely by blocking the binding of Raf1 to active Ras.

CONCLUSIONS: Our data establish RASSF1A as a novel inhibitor of cardiac hypertrophy by modulating the extracellular regulated kinase 1/2 pathway.

c-Met inhibition in a HOXA9/Meis1 model of CN-AML

BACKGROUND: Hematopoiesis is a paradigm for developmental processes, hierarchically organized, with stem cells at its origin. Hematopoietic stem cells (HSCs) replenish progenitor and precursor cells of multiple lineages, which normally differentiate into short-lived mature circulating cells. Hematopoiesis has provided insight into the molecular basis of tissue homeostasis and malignancy. Malignant hematopoiesis, in particular acute myeloid leukemia (AML), results from impaired development or differentiation of HSCs and progenitors. Co-overexpression of HOX and TALE genes, particularly the HOXA cluster and MEIS1, is associated with AML. Clinically relevant models of AML are required to advance drug development for an aging patient cohort.

RESULTS: Molecular analysis identified altered gene, microRNA, and protein expression in HOXA9/Meis1 leukemic bone marrow compared to normal controls. A candidate drug screen identified the c-Met inhibitor SU11274 for further analysis. Altered cell cycle status, apoptosis, differentiation, and impaired colony formation were shown for SU11274 in AML cell lines and primary leukemic bone marrow.

CONCLUSIONS: The clonal HOXA9/Meis1 AML model is amenable to drug screening analysis. The data presented indicate that human AML cells respond in a similar manner to the HOXA9/Meis1 cells, indicating pre-clinical relevance of the mouse model.

Redirection of T cells by delivering a transgenic mouse-derived MDM2 tumor antigen-specific TCR and its humanized derivative is governed by the CD8 coreceptor and affects natural human TCR expression.

Retroviral transfer of T cell antigen receptor (TCR) genes selected by circumventing tolerance to broad tumor- and leukemia-associated antigens in human leukocyte antigen (HLA)-A*0201 (A2.1) transgenic (Tg) mice allows the therapeutic reprogramming of human T lymphocytes. Using a human CD8 x A2.1/Kb mouse derived TCR specific for natural peptide-A2.1 (pA2.1) complexes comprising residues 81-88 of the human homolog of the murine double-minute 2 oncoprotein, MDM2(81-88), we found that the heterodimeric CD8 alpha beta coreceptor, but not normally expressed homodimeric CD8 alpha alpha, is required for tetramer binding and functional redirection of TCR- transduced human T cells. CD8+T cells that received a humanized derivative of the MDM2 TCR bound pA2.1 tetramers only in the presence of an anti-human-CD8 anti-body and required more peptide than wild-type (WT) MDM2 TCR+T cells to mount equivalent cytotoxicity. They were, however, sufficiently effective in recognizing malignant targets including fresh leukemia cells. Most efficient expression of transduced TCR in human T lymphocytes was governed by mouse as compared to human constant (C) alphabeta domains, as demonstrated with partially humanized and murinized TCR of primary mouse and human origin, respectively. We further observed a reciprocal relationship between the level of Tg WT mouse relative to natural human TCR expression, resulting in T cells with decreased normal human cell surface TCR. In contrast, natural human TCR display remained unaffected after delivery of the humanized MDM2 TCR. These results provide important insights into the molecular basis of TCR gene therapy of malignant disease.