Zinc transporters in prostate cancer

Prostate cancer is a major health concern as it has the second highest incidence rate among cancers in men. Despite progress in tumor diagnostics and therapeutic approaches, prognosis for men with advanced disease remains poor. In this review we provide insight into the changes of the intermediary metabolism in normal prostate and prostate cancer. In contrast to normal cells, prostate cancer cells are reprogrammed for optimal energy-efficiency with a functional Krebs cycle and minimal apoptosis rates. A key element in this relationship is the uniquely high zinc level of normal prostate epithelial cells. Zinc is transported by the SLC30 and SLC39 families of zinc transporters. However, in prostate cancer the intracellular zinc content is remarkably reduced and expression levels of certain zinc transporters are altered. Here, we summarize the role of different zinc transporters in the development of prostate cancer.

Solute carriers (SLCs) in cancer

During tumor progression cells acquire an altered metabolism, either as a cause or as a consequence of an increased need of energy and nutrients. All four major classes of macromolecules are affected: carbohydrates, proteins, lipids and nucleic acids. As a result of the changed needs, solute carriers (SLCs) which are the major transporters of these molecules are differently expressed. This renders them important targets in the treatment of cancer. Blocking or activating SLCs is one possible therapeutic strategy. For example, some SLCs are upregulated in tumor cells due to the increased demand for energy and nutritional needs. Thus, blocking them and turning off the delivery of fuel or nutrients could be one way to interfere with tumor progression. Specific drug delivery to cancer cells via transporters is another approach. Some SLCs are also interesting as chemosensitizing targets because blocking or activating them may result in an altered response to chemotherapy. In this review we summarize the roles of SLCs in cancer therapy and specifically their potential as direct or indirect targets, as drug carriers or as chemosensitizing targets.

CCND1/CyclinD1 status in metastasizing bladder cancer: a prognosticator and predictor of chemotherapeutic response

The CCND1 gene encodes the protein CyclinD1, which is an important promoter of the cell cycle and a prognostic and predictive factor in different cancers. CCND1 is amplified to a substantial proportion in various tumors, and this may contribute to CyclinD1 overexpression. In bladder cancer, information about the clinical relevance of CCND1/CyclinD1 alterations is limited. In the present study, amplification status of CCND1 and expression of CyclinD1 were evaluated by fluorescence in situ hybridization and immunohistochemistry on tissue microarrays from 152 lymph node-positive urothelial bladder cancers (one sample each from the center and invasion front of the primary tumors, two samples per corresponding lymph node metastasis) treated by cystectomy and lymphadenectomy. CCND1 amplification status and the percentage of immunostained cancer cells were correlated with histopathological tumor characteristics, cancer-specific survival and response to adjuvant chemotherapy. CCND1 amplification in primary tumors was homogeneous in 15% and heterogeneous in 6% (metastases: 22 and 2%). Median nuclear CyclinD1 expression in amplified samples was similar in all tumor compartments (60-70% immunostained tumor nuclei) and significantly higher than in non-amplified samples (5-20% immunostained tumor nuclei; P<0.05). CCND1 status and CyclinD1 expression were not associated with primary tumor stage or lymph node tumor burden. CCND1 amplification in primary tumors (P=0.001) and metastases (P=0.02) and high nuclear CyclinD1 in metastases (P=0.01) predicted early cancer-related death independently. Subgroup analyses showed that chemotherapy was particularly beneficial in patients with high nuclear CyclinD1 expression in the metastases, whereas expression in primary tumors and CCND1 status did not predict chemotherapeutic response. In conclusion, CCND1 amplification status and CyclinD1 expression are independent risk factors in metastasizing bladder cancer. High nuclear CyclinD1 expression in lymph node metastases predicts favorable response to chemotherapy. This information may help to personalize prognostication and administration of adjuvant chemotherapy.

Characterization and Clinical Relevance of ALDHbright Populations in Prostate Cancer

PURPOSE High aldehyde dehydrogenase (ALDH) has been suggested to selectively mark cells with high tumorigenic potential in established prostate cancer cell lines. However, the existence of cells with high ALDH activity (ALDH(bright)) in primary prostate cancer specimens has not been shown so far. We investigated the presence, phenotype, and clinical significance of ALDH(bright) populations in clinical prostate cancer specimens. EXPERIMENTAL DESIGN We used ALDEFLUOR technology and fluorescence-activated cell-sorting (FACS) staining to identify and characterize ALDH(bright) populations in cells freshly isolated from clinical prostate cancer specimens. Expression of genes encoding ALDH-specific isoforms was evaluated by quantitative real-time PCR in normal prostate, benign prostatic hyperplasia (BPH), and prostate cancer tissues. ALDH1A1-specific expression and prognostic significance were assessed by staining two tissue microarrays that included more than 500 samples of BPH, prostatic intraepithelial neoplasia (PIN), and multistage prostate cancer. RESULTS ALDH(bright) cells were detectable in freshly excised prostate cancer specimens (n = 39) and were mainly included within the EpCAM((+)) and Trop2((+)) cell populations. Although several ALDH isoforms were expressed to high extents in prostate cancer, only ALDH1A1 gene expression significantly correlated with ALDH activity (P < 0.01) and was increased in cancers with high Gleason scores (P = 0.03). Most importantly, ALDH1A1 protein was expressed significantly more frequently and at higher levels in advanced-stage than in low-stage prostate cancer and BPH. Notably, ALDH1A1 positivity was associated with poor survival (P = 0.02) in hormone-naïve patients. CONCLUSIONS Our data indicate that ALDH contributes to the identification of subsets of prostate cancer cells of potentially high clinical relevance.

From "magic bullets" to specific cancer immunotherapy

The immune system is able to specifically target antigen-expressing cancer cells. The promise of immunotherapy was to eliminate cancer cells without harming normal tissue and, therefore, with no or very few side effects. Immunotherapy approaches have, for several decades, been tested against several tumours, most often against malignant melanoma. However, although detectable immune responses have regularly been induced, the clinical outcome has often been disappointing. The development of molecular methods and an improved understanding of tumour immunosurveillance led to novel immunotherapy approaches in the last few years. First randomised phase III trials proved that immunotherapy can prolong survival of patients with metastatic melanoma or prostate cancer. The development in the field is very rapid and various molecules (mainly monoclonal antibodies) that activate the immune system are currently being tested in clinical trials and will possibly change our treatment of cancer. The ultimate goal of any cancer therapy and also immunotherapy is to cure cancer. However, this depends on the elimination of the disease originating cancer stem cells. Unfortunately, cancer stem cells seem resistant to most available treatment options. Recent developments in immunotherapy may allow targeting these cancer stem cells specifically in the future. In this review, we summarise the current state of immunotherapy in clinical routine and the expected developments in the near future.

The severity of neural invasion is associated with shortened survival in colon cancer

PURPOSE Neural invasion (NI) is a histopathologic feature of colon cancer that receives little consideration. Therefore, we conducted a morphologic and functional characterization of NI in colon cancer. EXPERIMENTAL DESIGN NI was investigated in 673 patients with colon cancer. Localization and severity of NI was determined and related to patient's prognosis and survival. The neuro-affinity of colon cancer cells (HT29, HCT-116, SW620, and DLD-1) was compared with pancreatic cancer (T3M4 and SU86.86) and rectal cancer cells (CMT-93) in the in vitro three-dimensional (3D)-neural-migration assay and analyzed via live-cell imaging. Immunoreactivity of the neuroplasticity marker GAP-43, and the neurotrophic-chemoattractant factors Artemin and nerve growth factor (NGF), was quantified in colon cancer and pancreatic cancer nerves. Dorsal root ganglia of newborn rats were exposed to supernatants of colon cancer, rectal cancer, and pancreatic cancer cells and neurite density was determined. RESULTS NI was detected in 210 of 673 patients (31.2%). Although increasing NI severity scores were associated with a significantly poorer survival, presence of NI was not an independent prognostic factor in colon cancer. In the 3D migration assay, colon cancer and rectal cancer cells showed much less neurite-targeted migration when compared with pancreatic cancer cells. Supernatants of pancreatic cancer and rectal cancer cells induced a much higher neurite density than those of colon cancer cells. Accordingly, NGF, Artemin, and GAP-43 were much more pronounced in nerves in pancreatic cancer than in colon cancer. CONCLUSION NI is not an independent prognostic factor in colon cancer. The lack of a considerable biologic affinity between colon cancer cells and neurons, the low expression profile of colonic nerves for chemoattractant molecules, and the absence of a major neuroplasticity in colon cancer may explain the low prevalence and impact of NI in colon cancer.

Targeted radiotherapy of prostate cancer with a gastrin-releasing peptide receptor antagonist is effective as monotherapy and in combination with rapamycin

UNLABELLED The gastrin-releasing peptide receptor (GRPr) is overexpressed in prostate cancer and is an attractive target for radionuclide therapy. In addition, inhibition of the protein kinase mammalian target of rapamycin (mTOR) has been shown to sensitize various cancer cells to the effects of radiotherapy. METHODS To determine the effect of treatment with rapamycin and radiotherapy with a novel (177)Lu-labeled GRPr antagonist ((177)Lu-RM2, BAY 1017858) alone and in combination, in vitro and in vivo studies were performed using the human PC-3 prostate cancer cell line. PC-3 cell proliferation and (177)Lu-RM2 uptake after treatment with rapamycin were assessed in vitro. To determine the influence of rapamycin on (177)Lu-RM2 tumor uptake, in vivo small-animal PET studies with (68)Ga-RM2 were performed after treatment with rapamycin. To study the efficacy of (177)Lu-RM2 in vivo, mice with subcutaneous PC-3 tumors were treated with (177)Lu-RM2 alone or after pretreatment with rapamycin. RESULTS Stable expression of GRPr was maintained after rapamycin treatment with doses up to 4 mg/kg in vivo. Monotherapy with (177)Lu-RM2 at higher doses (72 and 144 MBq) was effective in inducing complete tumor remission in 60% of treated mice. Treatment with 37 MBq of (177)Lu-RM2 and rapamycin in combination led to significantly longer survival than with either agent alone. No treatment-related toxicity was observed. CONCLUSION Radiotherapy using a (177)Lu-labeled GRPr antagonist alone or in combination with rapamycin was efficacious in inhibiting in vivo tumor growth and may be a promising strategy for treatment of prostate cancer.

Altered Responses to Endoplasmic Reticulum Stress in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) represents the fourth most common cause of cancer-associated death in the United States. Little progress has been made in understanding how proteotoxic stress affects rapidly proliferating pancreatic tumor cells. Endoplasmic reticulum (ER) stress occurs when protein homeostasis in the ER lumen is perturbed. ER stress activates the unfolded protein response (UPR) to reduce the protein load in the ER. Under conditions of moderate ER stress, the UPR promotes cell cycle arrest which allows time for successful protein load reduction and enables cell survival. However, under conditions of high levels of ER stress the UPR induces cellular apoptosis. In this dissertation, I investigated the role of endoplasmic reticulum (ER) stress and its effects on the cell cycle in pancreatic cancer cells. Activation of the unfolded protein response after ER stress induction was determined by comparing expression of key UPR mediators in non-tumorigenic pancreatic ductal cells to pancreatic cancer cells. Two arms of the UPR were assessed: eIF2α/ATF4/CHOP and IRE1α/XBP1s. Pancreatic cancer cells exhibited altered UPR activation characterized by a delay in both phosphorylation of eIF2α and induction of spliced XBP1. Further evaluation of the UPR-mediated effects on cell cycle progression revealed that pancreatic cancer cells showed a compromised ability to inhibit G1 to S phase progression after ER stress. This reduced ability to arrest proliferation was found to be due to an impaired ability to downregulate cyclin D1, a key gatekeeper of the G1/S checkpoint. Abrogation of cyclin D1 repression was mediated through a slow induction of phosphorylation of eIF2α, a critical mediator of translational attenuation in response to ER stress. In conclusion, pancreatic cancer cells demonstrate a globally compromised ability to regulate the unfolded protein response. This deficiency results in reduced cyclin D1 repression through an eIF2α-mediated mechanism. These findings indicate that pancreatic cancer cells have increased tolerance for elevated ER stress compared to normal cells, and this tolerance results in continued tumor cell proliferation under proteotoxic conditions.

LY2109761, a novel transforming growth factor beta receptor type I and type II dual inhibitor, as a therapeutic approach to suppressing pancreatic cancer metastasis.

Most pancreatic cancer patients present with inoperable disease or develop metastases after surgery. Conventional therapies are usually ineffective in treating metastatic disease. It is evident that novel therapies remain to be developed. Transforming growth factor beta (TGF-beta) plays a key role in cancer metastasis, signaling through the TGF-beta type I/II receptors (TbetaRI/II). We hypothesized that targeting TbetaRI/II kinase activity with the novel inhibitor LY2109761 would suppress pancreatic cancer metastatic processes. The effect of LY2109761 has been evaluated on soft agar growth, migration, invasion using a fibroblast coculture model, and detachment-induced apoptosis (anoikis) by Annexin V flow cytometric analysis. The efficacy of LY2109761 on tumor growth, survival, and reduction of spontaneous metastasis have been evaluated in an orthotopic murine model of metastatic pancreatic cancer expressing both luciferase and green fluorescence proteins (L3.6pl/GLT). To determine whether pancreatic cancer cells or the cells in the liver microenvironment were involved in LY2109761-mediated reduction of liver metastasis, we used a model of experimental liver metastasis. LY2109761 significantly inhibited the L3.6pl/GLT soft agar growth, suppressed both basal and TGF-beta1-induced cell migration and invasion, and induced anoikis. In vivo, LY2109761, in combination with gemcitabine, significantly reduced the tumor burden, prolonged survival, and reduced spontaneous abdominal metastases. Results from the experimental liver metastasis models indicate an important role for targeting TbetaRI/II kinase activity on tumor and liver microenvironment cells in suppressing liver metastasis. Targeting TbetaRI/II kinase activity on pancreatic cancer cells or the cells of the liver microenvironment represents a novel therapeutic approach to prevent pancreatic cancer metastasis.

ATM Signaling to TSC2: Mechanisms and Implications for Cancer Therapy

Ataxia telangiectasia mutated (ATM) is a critical component of the cellular response to DNA damage, where it acts as a damage sensor, and signals to a large network of proteins which execute the important tasks involved in responding to the damage, namely inducing cell cycle checkpoints, inducing DNA repair, modulating transcriptional responses, and regulating cell death pathways if the damage cannot be repaired faithfully. We have now discovered that an additional novel component of this ATM-dependent damage response involves induction of autophagy in response to oxidative stress. In contrast to DNA damage-induced ATM activation however, oxidative stress induced ATM, occurs in the cytoplasm, and does not require nuclear-to-cytoplasmic shuttling of ATM. Using several cell culture systems including MCF7 breast carcinoma cells, SKOV3 ovarian cancer cells, and various lineages of mouse embryonic fibroblasts, we showed that once activated by reactive oxygen species (ROS), ATM signals to mTORC1 to induce autophagy via the LKB1-AMPK-TSC2 pathway. Targeting dysregulation of mTORC1 in Atm-deficient mice, which succumb to lymphomagenesis within 3-4 months of age with daily administration of rapamycin, could significantly extend survival and cause regression of tumors, suggesting that pharmacologically targeting this pathway has therapeutic implications in cancer. We also identified a second contrasting pathway for DNA damage-induced mTORC1 repression which does not require AMPK activation, but does require ATM and TSC2. Several potential mechanisms including mTOR localization and p53-mediated pathways were ruled out however we identified that TSC2 may be an additional cytoplasmic direct ATM substrate that is engaged in response to DNA damage specifically. Lastly, a study was performed to examine whether autophagy induced by ovarian cancer therapeutics (focusing on cisplatin, since paclitaxel does not induce autophagy in the SKOV3 cell line model we used) plays a role in resistance to therapy since autophagy can play both pro-survival mechanisms or be a mechanism of cell death. Using a genetic approach to knock-down Atg5 expression with shRNA in SKOV3 ovarian carcinoma cells, we compared the cytotoxicity of cisplatin in vector or Atg5 knock-down cells, and demonstrated that autophagy does not play any significant role in the response to cisplatin in this cell line.

Significance of Increased Tissue Transglutaminase in Hormone Refractory Prostate Cancer

The progression of hormone responsive to hormone refractory prostate cancer poses a major clinical challenge in the successful treatment of prostate cancer. The hormone refractory prostate cancer cells exhibit resistance not only to castrate levels of testosterone, but also to other therapeutic modalities and hence become lethal. Currently, there is no effective treatment available for managing this cancer. These observations underscore the urgency to investigate mechanism(s) that contribute to the progression of hormone-responsive to hormone-refractory prostate cancer and to target them for improved clinical outcomes. Tissue transglutaminase (TG2) is a multifunctional pro-inflammatory protein involved in diverse physiological processes such as inflammation, tissue repair, and wound healing. Its expression is also implicated in pathological conditions such as cancer and fibrosis. Interestingly, we found that the androgen-independent prostate cancer cell lines, which lacked androgen receptor (AR) expression, contained high basal levels of tissue transglutaminase. Inversely, the cell lines that expressed androgen receptor lacked transglutaminase expression. This attracted our attention to investigate the possible role this protein may play in the progression of prostate cancer, especially in view of recent observations that its expression is linked with increased invasion, metastasis, and drug resistance in multiple cancer cell types. The results we obtained were rather surprising and revealed that stable expression of tissue transglutaminase in androgen-sensitive LNCaP prostate cancer cells rendered these cells independent of androgen for growth and survival by silencing the AR expression. The AR silencing in TG2 expressing cells (TG2-infected LNCaP and PC-3 cells) was due to TG2-induced activation of the inflammatory nuclear transcription factor-kB (NF-kB). Thus, TG2 induced NF-kB was found to directly bind to the AR promoter. Importantly, TG2 protein was specifically recruited to the AR promoter in complex with the p65 subunit of NF-kB. Moreover, TG2 expressing LNCaP and PC-3 cells exhibited epithelial-to-mesenchymal transition, as evidenced by gain of mesenchymal (such as fibronectin, vimentin, etc.) and loss of epithelial markers (such as E-cadherin, b-catenin). Taken together, these results suggested a new function for TG2 and revealed a novel mechanism that is responsible for the progression of prostate cancer to the aggressive hormone-refractory phenotype.

DOWNREGULATION OF PAX2 SUPPRESSES OVARIAN CANCER CELL GROWTH

PAX2 is one of nine PAX genes regulating tissue development and cellular differentiation in embryos. PAX2 promotes cell proliferation, oncogenic transformation, cell-lineage specification, migration, and survival. Unattenuated PAX2 has been found in several cancer types. We therefore sought to elucidate the role of PAX2 in ovarian carcinomas. We found that PAX2 was expressed in low-grade serous, clear cell, endometrioid and mucinous cell ovarian carcinomas, which are relatively chemoresistant compared to high grade serous ovarian carcinomas. Four ovarian cancer cell lines, RMUGL (mucinous), TOV21G (clear cell), MDAH-2774 (endometrioid) and IGROV1 (endometrioid), which express high-levels of PAX2, were used to study the function of PAX2. Lentiviral shRNAs targeting PAX2 were used to knock down PAX2 expression in these cell lines. Cellular proliferation and motility assays subsequently showed that PAX2 stable knockdown had slower growth and migration rates. Microarray gene expression profile analysis further identified genes that were affected by PAX2 including the tumor suppressor gene G0S2. Reverse phase protein array (RPPA) data showed that PAX2 knockdown affected several genes that are involved in apoptosis, which supports the fact that downregulation of PAX2 in PAX2-expressing ovarian cancer cells inhibits cell growth. We hypothesize that this growth inhibition is due to upregulation of the tumor suppressor gene G0S2 via induction of apoptosis. PAX2 represents a potential therapeutic target for chemoresistant PAX2-expressing ovarian carcinomas.

ECHOGENIC LIPOSOMES FOR NITRIC OXIDE DELIVERY AND BREAST CANCER TREATMENT

Liposomes, also known as nontoxic, biodegradable, and non-immunogenic therapeutic delivery vehicles, have been proposed as a carrier for drugs and antitumor agents in cancer chemotherapy. Echogenic liposomes (ELIP) have the potential to entrap air or bioactive gas to enhance acoustic reflectivity in ultrasound and are used as a contrast agent. The innovative part of this study is based on a novel concept to encapsulate nitric oxide (NO) gas into ELIP, deliver it to breast cancer cells, and control its release via direct ultrasound exposure. Studies on the effect of NO in tumor biology have shown that a high levels of NO (> 300 nM) leads to cytostasis or apoptosis by decreasing the translation of several cell cycle proteins and stimulating cancer cell death by activating the p53 pathway. The central hypothesis is that NO gas can be packaged and delivered through a delivery methodology to breast cancer cells to facilitate tumor regression with minimal systemic toxicity. The primary goal of this thesis is to develop an echogenic liposomal solution that has the ability to encapsulate NO, to release NO locally upon ultrasound exposure, and to induce breast cancer cell death. NO-containing echogenic liposomes (NO-ELIP) were prepared by the freezing-under-pressure method previously developed in our laboratory. It was necessary to evaluate stability of NO-ELIP and release of NO from NO-ELIP by measuring echogenicity using intravascular ultrasound images. Breast cancer cell lines, MDA-MB-231 and MDA-MB-468, were selected to investigate the cytotoxic effects of NO liberated from NO-ELIP and their response to NO concentration. Ultrasound-triggered NO release from NO-ELIP using ultrasound activation was studied. It was demonstrated that NO-ELIP remained stable for 5 hours in bovine serum albumin. Delivery of NO using NO-ELIP induced cytotoxicity and programmed cell death of MDA-MB-231 and MDA-MB-468 after 5 hours of incubation. Enhancement of the NO-ELIP effect for therapeutic application was observed with ultrasound activation. This work demonstrates that NO-ELIP can incorporate and deliver NO to breast cancer cells providing increased NO stability and ultrasound-controlled NO release. Improved therapeutic effect with the use of NO-ELIP is expected to be found for breast cancer treatment.

THE ROLE OF TAK1 IN PANCREATIC CANCER DEVELOPMENT

Pancreatic cancer is the fourth leading cause of cancer-related mortality in the United States and the fifth leading cause of cancer-related mortality worldwide. Pancreatic cancer is a big challenge in large due to the lack of early symptoms. In addition, drug resistance is a major obstacle to the success of chemotherapy in pancreatic cancer. The underlying mechanism of drug resistance in human pancreatic cancers is not well understood. Better understanding of the mechanism of molecular pathways in human pancreatic cancers can help to identify the novel therapeutic target candidates, and develop the new preventive and clinic strategies to improve patient survival. We discovered that TAK1 is overexpressed in pancreatic cancer cell lines and patient tumor tissues. We demonstrated that the elevated activity of TAK1 is caused by its binding partner TAB1. Knocking down of TAK1 in pancreatic cancer cells with RNAi technique resulted in cell apoptosis and significantly reduces the size of tumors in mice and made a chemotherapy drug more potent. Targeting the kinase activity of TAK1 with the selective inhibitor LY2610956 strongly synergized in vitro with the antitumor activity of gemcitabine, oxaliplatin, or irinotecan on pancreatic cancer cells. These findings highlighted that TAK1 could be a potential therapeutic target for pancreatic cancer. We also demonstrated that TAK activity is regulated by its binding protein TAB1. We defined a minimum TAB1 sequence which is required and sufficient for TAK1 kinase activity. We created a recombinant TAK1-TAB1 C68 fusion form which has highly kinase activity. This active form could is used for screening TAK1 inhibitors. In addition, several posttranslational modifications were identified in our study. The acetylation of lysine 158 on TAK1 is required for kinase activity. This site is conserved throughout all of kinase. Our findings may reveal a new mechanism by which kinase activity is regulated.

Prognostic significance of xCT polymorphisms and expression in patients with advanced pancreatic cancer treated with chemotherapy

The plasma membrane xc- cystine/glutamate transporter mediates cellular uptake of cystine in exchange for intracellular glutamate and is highly expressed by pancreatic cancer cells. The xCT gene, encoding the cystine-specific xCT protein subunit of xc-, is important in regulating intracellular glutathione (GSH) levels, critical for cancer cell protection against oxidative stress, tumor growth and resistance to chemotherapeutic agents including platinum. We examined 4 single nucleotide polymorphisms (SNPs) of the xCT gene in 269 advanced pancreatic cancer patients who received first line gemcitabine with or without cisplatin or oxaliplatin. Genotyping was performed using Taqman real-time PCR assays. A statistically significant correlation was noted between the 3' untranslated region (UTR) xCT SNP rs7674870 and overall survival (OS): Median survival time (MST) was 10.9 and 13.6 months, respectively, for the TT and TC/CC genotypes (p = 0.027). Stratified analysis showed the genotype effect was significant in patients receiving gemcitabine in combination with platinum therapy (n = 145): MST was 10.5 versus 14.1 months for the TT and TC/CC genotypes, respectively (p = 0.013). The 3' UTR xCT SNP rs7674870 may correlate with OS in pancreatic cancer patients receiving gemcitabine and platinum combination therapy. Paraffin-embedded core and surgical biopsy tumor specimens from 98 patients with metastatic pancreatic adenocarcinoma were analyzed by immunohistochemistry using an xCT specific antibody. xCT protein IHC expression scores were analyzed in relation to overall survival in 86 patients and genotype in 12 patients and no statistically significant association was found between the level of xCT IHC expression score and overall survival (p = 0.514). When xCT expression was analyzed in terms of treatment response, no statistically significant associations could be determined (p = 0.908). These data suggest that polymorphic variants of xCT may have predictive value, and that the xc- transporter may represent an important target for therapy in pancreatic cancer.