DNA repair protein levels vis-à-vis anticancer drug resistance in the human tumor cell lines of the National Cancer Institute drug screening program

From clinical management to personalized medicine: novel therapeutic approaches for ovarian clear cell cancer

Ovarian clear-cell cancer is a rare subtype of epithelial ovarian cancer with unique clinical and biological features. Despite optimal cytoreductive surgery and platinum-based chemotherapy being the standard of care, most patients experience drug resistance and a poor prognosis. Therefore, novel therapeutic approaches have been developed, including immune checkpoint blockade, angiogenesis-targeted therapy, ARID1A synthetic lethal interactions, targeting hepatocyte nuclear factor 1β, and ferroptosis. Refining predictive biomarkers can lead to more personalized medicine, identifying patients who would benefit from chemotherapy, targeted therapy, or immunotherapy. Collaboration between academic research groups is crucial for developing prognostic outcomes and conducting clinical trials to advance treatment for ovarian clear-cell cancer. Immediate progress is essential, and research efforts should prioritize the development of more effective therapeutic strategies to benefit all patients.

X-ray cross-complementing family: the bridge linking DNA damage repair and cancer

Genomic instability is a common hallmark of human tumours. As a carrier of genetic information, DNA is constantly threatened by various damaging factors that, if not repaired in time, can affect the transmission of genetic information and lead to cellular carcinogenesis. In response to these threats, cells have evolved a range of DNA damage response mechanisms, including DNA damage repair, to maintain genomic stability. The X-ray repair cross-complementary gene family (XRCC) comprises an important class of DNA damage repair genes that encode proteins that play important roles in DNA single-strand breakage and DNA base damage repair. The dysfunction of the XRCC gene family is associated with the development of various tumours. In the context of tumours, mutations in XRCC and its aberrant expression, result in abnormal DNA damage repair, thus contributing to the malignant progression of tumour cells. In this review, we summarise the significant roles played by XRCC in diverse tumour types. In addition, we discuss the correlation between the XRCC family members and tumour therapeutic sensitivity.

Effects of Xeroderma pigmentosum group C polymorphism on the likelihood of prostate cancer

Background

Numerous studies have assessed the association between xeroderma pigmentosum complementation group C (XPC) polymorphisms and susceptibility of prostate cancer (PCa); however, the findings remain inconsistent.

Methods

We performed an updated analysis utilizing data from electronic databases to obtain a more accurate estimation of the relationship between XPC rs2228001 A/C polymorphism and PCa risk. We further used in silico tools to investigate this correlation.

Results

Totally, 5,305 PCa cases and 6,499 control subjects were evaluated. When all studies pooled together, we detected no positive result (recessive genetic model: OR = 1.14, 95% CI = 0.93‐1.40, P_{heterogeneity} = 0.001, P = .212); nevertheless, the XPC rs2228001 A/C variant was associated with PCa risk in Asian descendants in the subgroup analysis (OR = 1.21, 95% CI = 1.01‐1.43, P_{heterogeneity} = 0.008, P = .034). In silico tools showed that more than 20 proteins can participate in the protein crosstalk with XPC. The expression of XPC was down‐regulated in all Gleason scores of prostate cancer.

Conclusions

The present study indicated that the XPC rs2228001 A/C variant may be associated with elevated PCa risk in Asian patients.

Elevated expression of pancreatic adenocarcinoma upregulated factor (PAUF) is associated with poor prognosis and chemoresistance in epithelial ovarian cancer

Pancreatic adenocarcinoma upregulated factor (PAUF) is a ligand of toll-like receptors (TLRs) and has been reported to be involved in pancreatic tumor development. However, the significance of PAUF expression in epithelial ovarian cancer remains unclear. We aimed to investigate the possible clinical significance of PAUF in epithelial ovarian cancer. We examined the link between PAUF and TLR4 in ovarian cancer cell lines. Recombinant PAUF induced cell activation and proliferation in ovarian cancer cell lines, whereas PAUF knockdown inhibited these properties. Subsequently, we assessed PAUF and TLR4 expression by immunohistochemistry on tissue microarray of 408 ovarian samples ranging from normal to metastatic. PAUF expression positively correlated with TLR4 expression. Overexpression of PAUF was associated with high-grade tumor (p = 0.014) and chemoresistant tumor (p = 0.017). Similarly, high expression of TLR4 correlated with advanced tumor stage (p = 0.002) and chemoresistant tumor (p = 0.001). Multivariate analysis indicated that PAUF^high, TLR4^high, and PAUF^high/TLR4^high expression are independent prognostic factor for progression-free survival, while TLR4^high and PAUF^high/TLR4^high expression were independent prognostic factors for overall survival. Our results suggest that PAUF has a role in ovarian cancer progression and is a potential prognostic marker and novel chemotherapeutic target for ovarian cancer.

Fibroblast growth factor receptor 4 induced resistance to radiation therapy in colorectal cancer

In colorectal cancer (CRC), fibroblast growth factor receptor 4 (FGFR4) is upregulated and acts as an oncogene. This study investigated the impact of this receptor on the response to neoadjuvant radiotherapy by analyzing its levels in rectal tumors of patients with different responses to the therapy. Cellular mechanisms of FGFR4-induced radioresistance were analyzed by silencing or over-expressing FGFR4 in CRC cell line models. Our findings showed that the FGFR4 staining score was significantly higher in pre-treatment biopsies of non-responsive than responsive patients. Similarly, high expression of FGFR4 inhibited radiation response in cell line models. Silencing or inhibition of FGFR4 resulted in a reduction of RAD51 levels and decreased survival in radioresistant HT29 cells. Increased RAD51 expression rescued cells in the siFGFR4-group. In radiosensitive SW480 and DLD1 cells, enforced expression of FGFR4 stabilized RAD51 protein levels resulting in enhanced clearance of γ-H2AX foci and increased cell survival in the mismatch repair (MMR)-proficient SW480 cells. MMR-deficient DLD1 cells are defective in homologous recombination repair and no FGFR4-induced radioresistance was observed. Based on our results, FGFR4 may serve as a predictive marker to select CRC patients with MMR-proficient tumors who may benefit from pre-operative radiotherapy.

Proteins regulating the intercellular transfer and function of P-glycoprotein in multidrug-resistant cancer

Chemotherapy is an essential part of anticancer treatment. However, the overexpression of P-glycoprotein (P-gp) and the subsequent emergence of multidrug resistance (MDR) hampers successful treatment clinically. P-gp is a multidrug efflux transporter that functions to protect cells from xenobiotics by exporting them out from the plasma membrane to the extracellular space. P-gp inhibitors have been developed in an attempt to overcome P-gp-mediated MDR; however, lack of specificity and dose limiting toxicity have limited their effectiveness clinically. Recent studies report on accessory proteins that either directly or indirectly regulate P-gp expression and function and which are necessary for the establishment of the functional phenotype in cancer cells. This review discusses the role of these proteins, some of which have been recently proposed to comprise an interactive complex, and discusses their contribution towards MDR. We also discuss the role of other pathways and proteins in regulating P-gp expression in cells. The potential for these proteins as novel therapeutic targets provides new opportunities to circumvent MDR clinically.

Inhibition of DNA-repair genes Ercc1 and Mgmt enhances temozolomide efficacy in gliomas treatment: a pre-clinical study

Gliomas are the most common primary brain tumors. To date, therapies do not allow curing patients, and glioblastomas (GBMs) are associated with remarkably poor prognosis. This situation is at least partly due to intrinsic or acquired resistance to treatment, especially to chemotherapy. In 2005, temozolomide (TMZ) has become the first chemotherapeutic drug validated for GBM. Nevertheless TMZ efficacy depends on Mgmt status. While the methylation of Mgmt promoter was considered so far as a prognostic marker, its targeting is becoming an effective therapeutic opportunity. Thus, arrival of both TMZ and Mgmt illustrated that considerable progress can still be realized by optimizing adjuvant chemotherapy. A part of this progress could be accomplished in the future by overcoming residual resistance. The aim of the present study was to investigate the involvement of a set of other DNA-repair genes in glioma resistance to temozolomide. We focused on DNA-repair genes located in the commonly deleted chromosomal region in oligodendroglioma (1p/19q) highly correlated with patient response to chemotherapy. We measured effects of inhibition of ten DNA-repair genes expression using siRNAs on astrocytoma cell response to cisplatin (CDDP) and TMZ. SiRNAs targeting ercc1, ercc2, mutyh, and pnkp significantly sensitized cells to chemotherapy, increasing cell death by up to 25%. In vivo we observed a decrease of subcutaneous glioma tumor growth after injection of siRNA in conjunction with absorption of TMZ. We demonstrated in this pre-clinical study that targeting of DNA-repair genes such as Ercc1 could be used as an adjuvant chemosensitization treatment, similarly to Mgmt inhibition.

Plasmodium falciparum XPD translocates in 5' to 3' direction, is expressed throughout the blood stages, and interacts with p44

XPD helicase, a TFIIH subunit, is essential for several processes including transcription, NER, cell cycle regulation, and apoptosis in eukaryotes. Another component of TFIIH, namely p44, is among the well-known interacting partners of XPD and is vital in regulating the helicase activities of latter. However, none of the above mentioned proteins have been functionally characterized in Plasmodium falciparum. Consequently, in this study, we performed detailed studies on XPD and its interacting partner, p44, from P. falciparum 3D7 strain. Accordingly, we expressed and purified recombinant PfXPD and its fragments and Pfp44 proteins and characterized the enzymatic activities of PfXPD and its fragments. The in vivo stage-specific expression and subcellular localizations of PfXPD and Pfp44 proteins were studied using the specific antibodies in the intraerythrocytic developmental stages of P. falciparum 3D7 strain. Our results suggest that PfXPD displays the characteristic ssDNA-dependent ATPase and 5'-3' DNA helicase activities. We also report the existence of two high molecular weight forms of p44 in P. falciparum 3D7 strain. Both PfXPD and Pfp44 colocalize in the nucleus and interact with each other, which suggest that they are most likely components of the same complex apparently, TFIIH. Furthermore, during trophozoite and schizont stages, both proteins exhibit a distinct cytoplasmic distribution pattern which implies that PfXPD and Pfp44 might also be involved in other functions. These studies will aid in understanding the basic biology of malaria parasite.

Ursodeoxycholic acid effectively kills drug-resistant gastric cancer cells through induction of autophagic death

Carcinoma cells that have acquired drug resistance often exhibit cross-resistance to various other cytotoxic stimuli. Here, we investigated the effects of ursodeoxycholic acid (UDCA), a gastrointestinal tumor-suppressor, on a cisplatin‑resistant SNU601 gastric cancer subline (SNU601/R). While other anticancer drugs, including L-OHP, etoposide, and death ligand TRAIL, had minimal effects on the viability of these resistant cells, they were sensitive to UDCA. The UDCA‑induced reduction in the viability of the SNU601/R cells was accomplished through autophagy while the primary means of cell death in the parental SNU601 cells (SNU601/WT) was apoptosis. Previously, we demonstrated that the UDCA-triggered apoptosis of gastric cancer cells was regulated by a cell surface death receptor, TRAIL-R2/DR5, which was upregulated and re-distributed on lipid rafts. The UDCA stimulation of TRAIL-R2/DR5 also occurred in the SNU601/R cells despite the lack of apoptosis. In the present study, we found that CD95/Fas, another cell surface death receptor, was also translocated into lipid rafts in response to UDCA although it was not involved in the decrease in cell viability. Specifically, raft relocalization of CD95/Fas was triggered by UDCA in the SNU601/WT cells in which apoptosis occurred, but not in the SNU601/R cells where autophagic death occurred. Notably, UDCA reduced ATG5 levels, an essential component of autophagy, in the SNU601/WT, but not in the SNU601/R cell line. Moreover, in CD95/Fas-silenced SNU601/WT cells, UDCA did not decrease ATG5 levels and induced autophagic cell death rather than apoptosis. These results imply that raft‑distributed CD95/Fas may support UDCA-induced apoptosis via downregulation of ATG5 levels, preventing the autophagic pathway. Taken together, these results suggest that UDCA induces both apoptotic and autophagic cell death depending on the intracellular signaling environment, thereby conferring the advantage to overcome drug resistance through apoptotic defects.

Rad51 expression is a useful predictive factor for the efficacy of neoadjuvant chemoradiotherapy in squamous cell carcinoma of the esophagus

BACKGROUND

Neoadjuvant chemoradiotherapy (NACRT) for esophageal squamous cell carcinoma (ESCC) is beneficial in the setting of a complete pathological response. Rad51 expression affects both chemo- and radiosensitivity in many cancers; however, its role in ESCC is unclear.

METHODS

Rad51 expression was investigated by immunohistochemical staining with resected specimens in 89 ESCC patients who underwent surgery without preoperative therapy. The association with Rad51 and clinicopathological factors was assessed. The expression of Rad51 was also investigated in pretreatment biopsy specimens in 39 ESCC patients who underwent surgery after NACRT and compared with the pathological response to NACRT.

RESULTS

Lymph node metastasis was more frequently observed in Rad51-positive cases than negative cases (58.5 vs. 30.6%, P = 0.0168) in patients treated with surgery alone. Disease-specific survival was decreased in Rad51-positive cases compared to Rad51-negative cases (5 year survival: 79.6 vs. 59.3%, P = 0.0324). In NACRT patients, completed pathological responses were more frequently observed in Rad51-negative cases than in Rad51-positive cases (68.8 vs. 46.5%, P = 0.0171).

CONCLUSIONS

Rad51 expression in ESCC was associated with lymph node metastasis and poor survival. Additionally, Rad51 expression in pretreatment biopsy specimens was a predictive factor for the response to NACRT.

Expression and significance of the TLR4/MyD88 signaling pathway in ovarian epithelial cancers

BACKGROUND

Toll-like receptors (TLR) are a family of pattern recognition receptors that constitutes a major part of the innate immune system. The TLR4/(Myeloid differentiation factor 88 (MyD88) signaling pathway has been shown to have oncogenic effects.

METHODS

To demonstrate the role of TLR4/MyD88 signaling in ovarian epithelial cancers (OECs), we examined the expression of TLR4, MyD88 and nuclear factor- κB (NF-κB) in OECs. The expression of TLR4, MyD88, and NF-κB was detected by immunohistochemistry, and the relationships between these and clinicopathologic features in 123 cases of OECs were also analyzed.

RESULTS

The expression of TLR4, MyD88, and NF-κB in OECs was observed in 46.3% (57/123), 36.6% (45/123) and 65% (80/123) of OEC cases, respectively. The TLR4, MyD88, and NF-κB expressions were associated with the histologic type of OECs, particularly with the clear cell type of OEC. There was no significant correlation between TLR4 or NF-κB expression and histologic grade, tumor size, mitotic count, FIGO (International Federation of Gynecology and Obstetrics) stage, disease recurrence. However, there was a significant correlation between MyD88 expression and FIGO stage, disease recurrence as well as histologic type. In univariate analysis, the expression of TLR4 and MyD88, and the coexpression of TLR4/MyD88 and TLR4/MyD88/NF-κB had a significant impact on the survival of patients with OECs. Only MyD88 expression had an independent prognostic significance in multivariate analysis.

CONCLUSIONS

Our findings suggest that the TLR4/MyD88 signaling pathway is associated with the survival of patients with OECs, and that MyD88 is an independent prognostic predictor in patients with OECs. The TLR4/MyD88 signaling pathway may be a mechanism responsible for poor prognosis in patients with clear cell type of OEC.

Oxaliplatin as a radiosensitiser for upper and lower gastrointestinal tract malignancies: what have we learned from a decade of translational research?

Some of the greatest advances in the treatment of solid malignancies have resulted from the combination of chemotherapy and radiotherapy treatments. This article comprehensively reviews the current clinical evidence for oxaliplatin-based chemo-radiotherapy that may improve local control and survival. In order to understand how clinical studies should be designed, the pre-clinical evidence for the use of oxaliplatin chemotherapy as a radiosensitising agent is appraised. Particular focus is placed on oxaliplatin's biological mechanisms of action, including cell cycle effects, the formation of DNA adducts and interstrand cross-links and the role of DNA repair proteins. At a clinical level, there is currently no evidence to suggest that oxaliplatin provides an additional benefit to concurrent chemo-radiation regimes that utilise fluoropyrimidines; we evaluate the reasons for this observation, the limitations of clinical trial design and the opportunities that currently exist to design clinical trials which are underpinned by an understanding of the basic biology.

Functional characterization of osteosarcoma cell lines provides representative models to study the human disease

Cancer cell lines represent in vitro models for studying malignancies, general cell biology, drug discovery and more. Whether they can be considered as exact representative models of the parental tumors remains uncertain given the acquisition of additional ex vivo changes of the cells and the lack of tissue architecture and stroma. Previously, within the EuroBoNeT consortium, we characterized a collection of bone sarcoma cell lines on genomic and proteomic level. Here, we address the phenotypical and functional characterization of the unique set of osteosarcoma cell lines (n=19) in vitro and in vivo. For functional analysis of differentiation capacity, cells were stimulated towards osteoblasts, adipocytes and chondrocytes. Furthermore, all cell lines were injected subcutaneously and intramuscularly into nude mice to assay their in vivo tumor formation capacity as well as for phenotypical analysis of the tumors. All formed tumors were further characterized histologically and immunohistochemically. Out of 19 cell lines, 17 (89%) showed adipogenic differentiation, 13/19 (68%) could differentiate towards osteoblasts and in 6/19 (32%) cell lines chondrogenic differentiation was evident. About half of the cell lines (8/19, 42%) produced tumors in vivo after subcutaneous and intramuscular injections. Several cell lines showed invasion into adjacent tissues and one tumor developed several lung metastases. The use of cell lines, especially in cancer research, is of paramount importance. Here, we identify comprehensively characterized osteosarcoma cell lines, which robustly represent clinical osteosarcoma providing researchers useful in vitro and in vivo models to study the genetics and functional characteristics of this highly malignant neoplasm.

The effect of a DNA repair gene on cellular invasiveness: XRCC3 over-expression in breast cancer cells

Over-expression of DNA repair genes has been associated with resistance to radiation and DNA-damage induced by chemotherapeutic agents such as cisplatin. More recently, based on the analysis of genome expression profiling, it was proposed that over-expression of DNA repair genes enhances the invasive behaviour of tumour cells. In this study we present experimental evidence utilizing functional assays to test this hypothesis. We assessed the effect of the DNA repair proteins known as X-ray complementing protein 3 (XRCC3) and RAD51, to the invasive behavior of the MCF-7 luminal epithelial-like and BT20 basal-like triple negative human breast cancer cell lines. We report that stable or transient over-expression of XRCC3 but not RAD51 increased invasiveness in both cell lines in vitro. Moreover, XRCC3 over-expressing MCF-7 cells also showed a higher tumorigenesis in vivo and this phenotype was associated with increased activity of the metalloproteinase MMP-9 and the expression of known modulators of cell-cell adhesion and metastasis such as CD44, ID-1, DDR1 and TFF1. Our results suggest that in addition to its' role in facilitating repair of DNA damage, XRCC3 affects invasiveness of breast cancer cell lines and the expression of genes associated with cell adhesion and invasion.

Cellular and molecular mechanisms for the synergistic cytotoxicity elicited by oxaliplatin and pemetrexed in colon cancer cell lines

Purpose

Oxaliplatin effect in the treatment of colorectal cancer is improved upon combination with thymidylate synthase (TS) inhibitors. Pemetrexed is polyglutamated by the folylpolyglutamate synthase (FPGS) and blocks folate metabolism and DNA synthesis by inhibiting TS, dihydrofolate reductase (DHFR) and glycinamide ribonucleotide formyltransferase (GARFT). The present study evaluates the pharmacological interaction between oxaliplatin and pemetrexed in colorectal cancer cells.

Methods

Human HT29, WiDr, SW620 and LS174T cells were treated with oxaliplatin and pemetrexed. Drug interaction was studied using the combination index method, while cell cycle was investigated with flow cytometry. The effects of drugs on Akt phosphorylation and apoptosis were studied with ELISA and fluorescence microscopy, respectively. RT-PCR analysis was performed to assess whether drugs modulated the expression of pemetrexed targets and of genes involved in DNA repair (ERCC1 and ERCC2). Finally, platinum–DNA adduct levels were detected by ultra-sensitive multi-collector inductively coupled plasma mass spectrometry (ICP-MS).

Results

A dose-dependent inhibition of cell growth was observed after drug exposure, while a synergistic interaction was detected preferentially with sequential combinations. Oxaliplatin enhanced cellular population in the S-phase. Drug combinations increased apoptotic indices with respect to single agents, and both drugs inhibited Akt phosphorylation. RT-PCR analysis showed a correlation between the FPGS/(TS × DHFR × GARFT) ratio and pemetrexed sensitivity, as well as a downregulation of ERCC1, ERCC2, TS, DHFR and GARFT after drug exposure. In addition, pretreatment with pemetrexed resulted in an increase of oxaliplatin–DNA adducts.

Conclusion

These data demonstrate that oxaliplatin and pemetrexed synergistically interact against colon cancer cells, through modulation of cell cycle, inhibition of Akt phosphorylation, induction of apoptosis and modulation of gene expression.

Ovarian cancer: pathology, biology, and disease models

Epithelial ovarian cancer, which comprises several histologic types and grades, is the most lethal cancer among women in the United States. In this review, we summarize recent progress in understanding the pathology and biology of this disease and in development of models for preclinical research. Our new understanding of this disease suggests new targets for therapeutic intervention and novel markers for early detection of disease.

DNA repair gene polymorphisms affect cytotoxicity in the National Cancer Institute Human Tumour Cell Line Screening Panel

Polymorphisms in DNA repair genes have been suggested to increase the risk of cancer and other diseases, but the epidemiological studies are often not consistent, and the results confusing. We have examined the effect of polymorphisms in base and nucleotide excision-repair genes, as well as regulatory and signalling genes, on cytotoxic sensitivity of tumour cell lines used for screening anticancer drugs by the National Cancer Institute. It was found that for the TP53 P72R and ERCC2 D312N polymorphisms, the heterozygous genotype was most sensitive, while for the OGG1 S326C and NOS3 g.-786T>C polymorphisms the homozygous-variant genotype was most sensitive. The biggest increase in sensitization was found with the XRCC1 R399Q homozygous dominant genotype. The sensitization was found across a broad range of drugs, indicating the importance of DNA repair responses. It was also found that while the other gene polymorphisms were in Hardy-Weinberg equilibrium, the TP53 P72R heterozygous genotype was relatively depleted. For the OGG1 polymorphism, the repair of 8-oxo-guainine from DNA was measured in three panel cell lines that differed in their OGG1 genotype. The cell line with the homozygous-variant genotype had a much poorer repair than the other genotypes, as predicted. The correlation of polymorphisms with cytotoxicity may be an approach to understanding their effects which may be difficult to reveal in epidemiological studies.

Mechanisms of chemoresistance and poor prognosis in ovarian clear cell carcinoma

Clear cell carcinoma (CCC) accounts for 4% to 12% of epithelial ovarian cancer in Western countries and, for some unknown reasons, it comprises more than 20% of such cancers in Japan. CCC shows unique clinical features such as a high incidence of stage I disease, a large pelvic mass, an increased incidence of vascular thromboembolic complications, and hypercalcemia. It is frequently associated with endometriosis. Compared to serous adenocarcinoma (SAC), CCC is relatively resistant to conventional platinum, or taxane-based chemotherapy which is associated with its poor prognosis. However, the mechanisms underlying CCC's resistance to chemotherapy have not been understood. Although several mechanisms involved in drug resistance exist in CCC, including decreased drug accumulation, increased drug detoxification, and an increased DNA repair activity; however, no particular chemoresistance system has been identified. On the other hand, an in vitro study revealed that low cell proliferation may cause the insensitivity of CCC to cisplatin. The Ki-67 labeling index in CCC tumors was significantly lower than SAC. The Ki-67 labeling index for responders was significantly higher than that for non-responders in both tumor types. A multivariable analysis revealed that Ki-67 labeling index and residual tumor size were independent prognostic factors in CCC. Therefore, lower proliferation of the tumor cells may contribute to their resistance to chemotherapy. However, further investigation into the molecular biology and genetics of CCC is warranted. This review discusses the current state of knowledge of the chemoresistance mechanism in CCC and novel treatment strategies for CCC.

Determination of ERCC2 Lys751Gln and GSTP1 Ile105Val gene polymorphisms in colorectal cancer patients: relationships with treatment outcome

INTRODUCTION

Glutathione S-transferase P1 (GSTP1) and excision-repair cross-complementing repair deficiency group 2 protein (ERCC2 or XPD) may modulate the activity of platinum derivatives. The SNPs, Ile105Val for GSTP1 and Lys751Gln for ERCC2, may affect the efficiency of oxaliplatin in patients treated with an oxaliplatin-based regimen for metastatic colorectal carcinoma.

PATIENTS & METHODS

A total of 107 patients treated with first-line chemotherapy, 59 with an oxaliplatin-based regimen and 48 with an irinotecan-based regimen, were included retrospectively. GSTP1 and ERCC2 genotypes were identified on DNA samples extracted from paraffin blocks containing either normal tissue (nodes) or tumor tissue. We analyzed treatment response, event-free and overall survival.

RESULTS

GSTP1 genotype distribution was Ile/Ile 58%, Ile/Val 35% and Val/Val 7%. ERCC2 genotype distribution was Lys/Lys 49%, Lys/Gln 44%, Gln/Gln 7%. Event-free and overall survivals were not significantly different as a function of the GSTP1 genotype, whatever the treatment received. Event-free survival was significantly different as a function of the ERCC2 genotype only in patients receiving oxaliplatin: patients having at least one variant allele had a shorter median event-free survival (6 months) than those having no variant allele (11.6 months, p = 0.008). This difference was maintained for median overall survival (15.6 vs 25.3 months, p = 0.016). Using univariate analysis, ERCC2 genotype, hemoglobinemia and carbohydrate antigen 19.9 plasma levels were significantly related to overall and event-free survival in patients receiving oxaliplatin.

CONCLUSION

The ERCC2 genotype appears as an important predictive factor of the survival of patients treated with oxaliplatin in first-line therapy for metastatic colorectal cancer.

Polymorphism of the DNA repair enzyme XRCC1 is associated with treatment prediction in anthracycline and cyclophosphamide/methotrexate/5-fluorouracil-based chemotherapy of patients with primary invasive breast cancer

OBJECTIVES

Outcome and survival in anthracycline-based and cyclophosphamide/methotrexate/5-fluorouracil-based chemotherapy of invasive breast cancer are unpredictable. Insights into treatment prediction are expected from studies searching for an association between genetic polymorphisms and treatment outcome effects. A common feature of treatment with chemoreagents is therapeutically induced DNA damage. Therefore, we tested the hypothesis of a relationship between event-free survival and genotype distributions of seven polymorphic DNA repair enzymes and four cell cycle regulators.

BASIC METHODS

This case-case comparison included 180 patients with primary invasive breast cancer diagnosed between 1986 and 2000 and subjected to adjuvant chemotherapy (anthracycline/cyclophosphamide or cyclophosphamide/methotrexate/5-fluorouracil). Ninety-two patients were reported without recurrence and 88 were reported with recurrences or dead. Median clinical follow-up was 61.7 months. Constitutional DNA isolated from archived tissues was genotyped at 19 loci by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Statistical analyses included adjusted risk estimates, Kaplan-Meier analyses, Cox proportional hazard model, and permutation testing.

MAIN RESULTS

Carriers of the XRCC1_1196_AA genotype had a reduced risk for recurrence/death (odds ratio adjusted 0.19; 95% confidence interval: 0.06-0.61), which was observed in survival analyses of all patients (P=0.003) and patients treated with chemotherapy but not radiotherapy (P=0.006). Multivariate analysis confirmed XRCC1 as a potential treatment predictor (hazard ratio 0.62; 95% confidence interval: 0.43-0.89). The result was stable upon permutation testing. No other significant associations were observed.

CONCLUSION

The DNA repair enzyme XRCC1 is a potential treatment predictor for the outcome and survival of anthracycline and cyclophosphamide/methotrexate/5-fluorouracil-based chemotherapy of invasive breast cancer.

Polymorphisms of phase II xenobiotic-metabolizing and DNA repair genes and in vitro N-ethyl-N-nitrosourea-induced O6-ethylguanine levels in human lymphocytes

This study tested the hypothesis that genetic variants of phase II detoxification enzymes and DNA repair proteins affect individual response to DNA damage from alkylating agents. In 171 healthy individuals, an immunoslot blot assay was used to measure O6-ethylguanosine (O6-EtGua) adduct levels in peripheral blood lymphocytes treated with N-ethyl-N-nitrosourea (ENU) in vitro. The genotypes of GSTM1, GSTT1, GSTP1 I(105)V and A(114)V, MGMT L(84)F and I(143)V, XPD D(312)N and K(751)Q, and XRCC3 T(241)M were determined. Demographic and exposure information was collected by in-person interview. Student's t-test, analysis of (co)variance, and multiple linear regression models were used in statistical analyses. The mean and median (range) O6-EtGua levels were 94.6 and 84.8 (3.2-508.1)fmol/g DNA, respectively. The adduct level was significantly lower in people who smoked >or=25 years than that in never-smokers (square-root transformed mean values 8.20 versus 9.37, P=0.03). Multiple linear regression models revealed that GSTT1 (beta=-2.36, P=0.009) polymorphism was a significant predictor of the level of adducts in 82 never-smokers, whereas the number of years smoked (beta=-0.08, P=0.005) and XRCC3 T(241)M (beta=2.22, P=0.007) in 89 ever-smokers. The association between GSTP1 I(105)V, MGMT I(143)V, and XPD D(312)N with the level of adducts was not conclusive. Each polymorphism could explain 2-10% of the variation of the adduct level. These observations suggest that GSTT1 null and XRCC3 T(241)M polymorphism may have some functional significance in modulating the level of ENU-induced DNA damage and these effects are smoking-dependent. Results from this exploratory study need to be confirmed in other experimental systems.

Relationships between genetic polymorphisms and anticancer drug cytotoxicity vis-à-vis the NCI-60 panel

INTRODUCTION

The National Cancer Institute (NCI)-60 panel consists of 60 human tumor cell lines initially established for screening thousands of molecules for antiproliferative activity. It has been powerful for deciphering the relationships between anticancer drug cytotoxicity and cell molecular characteristics. We tested its potential interest for establishing relationships between the polymorphism of genes involved in drug metabolism and transport or in DNA repair, and drug cytotoxicity extracted from NCI databases.

METHODS

Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques, three frequent single nucleotide polymorphisms (SNPs) were analyzed: Lys751Gln in the Xeroderma pigmentosum complementation group D (XPD, ERCC2) gene, Asp1104His in the Xeroderma pigmentosum complementation group G (XPG, ERCC5) gene and Ile105Val in the glutathione S-transferase P1 (GSTP1) gene.

RESULTS

The allelic frequencies of the variants were 33% for ERCC2, 23% for ERCC5 and 39% for GSTP1. The ERCC2 polymorphism appeared to be a strong determinant of the in vitro cytotoxicity of most anticancer agents, with lower half maximal inhibitory concentration (IC50) values in variant homozygous lines than in common homozygous or heterozygous cell lines. Unexpectedly, the cytotoxicity of taxanes appeared markedly dependent upon the ERCC2 genotype, with threefold lower mean IC50 values in variant homozygous cell lines. The ERCC5 genotype appeared to be important only for taxanes, with fourfold higher IC50 values in variant homozygous cell lines. The GSTP1 polymorphism was related to the cytotoxicity of several drug classes, especially topoisomerase inhibitors, antimetabolites and N7 alkylating agents.

CONCLUSION

The NCI-60 panel is capable of providing clues and tracks for the establishment of clinically useful relationships between a given genotype and the cytotoxicity of an anticancer agent.

Ovarian clear cell adenocarcinoma: a continuing enigma

Ovarian clear cell adenocarcinomas (OCCAs) account for <5% of all ovarian malignancies. Compared to other epithelial ovarian cancer (EOC) subtypes, when at an advanced stage, they are associated with a poorer prognosis and are relatively resistant to conventional platinum-based chemotherapy. By contrast, early-stage clear cell ovarian cancer carries a relatively good prognosis. Hence, there is a need to improve our understanding of its pathobiology in order to optimise currently available treatments and develop new therapeutic strategies. This review summarises the currently available literature regarding the pathogenesis of OCCA, its molecular genetic features and postulated molecular mechanisms that underlie its chemoresistant phenotype. Marked similarities with clear cell carcinomas of the kidney and endometrium have been noted by some investigators, raising interesting possibilities regarding novel therapeutic approaches. Unfortunately, most studies on OCCA have hitherto been hampered by insufficient sample sizes, leaving many key issues unresolved. It is envisaged that in the future, high-resolution genomic and gene-expression microarray studies incorporating larger sample sizes will lead to the characterisation of the key molecular players in OCCA biology, which may potentially lead to the identification of novel targets for therapeutic development.

Regulation of DNA repair gene expression in human cancer cell lines

Although most advanced cancers are incurable, the majority of testicular germ cell tumors can be cured using cisplatin-based combination chemotherapy. The nucleotide excision repair (NER) pathway removes most DNA adducts produced by cisplatin, and the low levels of NER in testis tumor cells may explain why these cancers are curable. Three NER proteins: ERCC1, XPF, and XPA, are present at low levels in testis tumor cell lines, and addition of these proteins to protein extracts of testis tumor cells increases their in vitro DNA repair capacity to normal levels. The aim of this study was to identify the mechanism responsible for the low levels of these DNA repair proteins. The levels of the mRNA transcripts for ERCC1, XPF, and XPA were measured in a panel of 14 different human cancer cell lines, using real-time PCR. Three ERCC1 splice variants were identified and quantitated. Three alternative transcription start points (TSPs) were identified for ERCC1 but none were testis-specific. The significantly lower levels of ERCC1, XPF, and XPA protein in testis tumor cell lines cannot be explained solely by differences in transcriptional efficiency or mRNA stability. For ERCC1, post-transcriptional control by alternative splicing does not account for the testis-specific low levels of protein expression. Pulse-chase experiments showed that the half-life of ERCC1 protein in a testis tumor cell line was not significantly different to that in a prostate cancer cell line. Taken together, these results suggest that constitutive levels of these DNA repair proteins are controlled at the level of translation.

Identification of MMS19 domains with distinct functions in NER and transcription

Nucleotide excision repair (NER) and RNA polymerase II (Pol II) transcription are essential cellular processes which are intimately intertwined. They share an indispensable multiprotein complex, TFIIH, and impairments in either process can impact the efficiency of the other. Like TFIIH, MMS19 is required for NER and Pol II transcription, but its precise role in each process is unknown. We showed previously that the human MMS19 gene originates multiple splice variants, some of which may encode distinct MMS19 protein isoforms. Here we characterize a novel MMS19 transcript and demonstrate for the first time that MMS19 splice variants are conserved across species and are functionally distinct. Expression of human MMS19 splice variants in mms19-deleted yeast cells produced unique patterns of thermosensitivity and ultraviolet radiation-sensitivity that point to three MMS19 structural domains with distinct in vivo functions. MMS19 polypeptides lacking domain A are able to fulfill the role of full-length MMS19 in NER but not in transcription. MMS19 polypeptides lacking part of domain B are efficient in transcription but not in NER. MMS19 polypeptides lacking domain C (HEAT repeats) are unable to fulfill either function. Our data suggest that the MMS19 HEAT repeat domain is essential for MMS19 function in NER and transcription, while domains A and B, within MMS19 N-terminus, modulate the balance between DNA repair and transcription. Our results highlight the functional significance of MMS19 transcripts and the possible contribution of MMS19 isoforms to regulate the switch between NER and transcription. Furthermore, our work associates for the first time specific protein domains with MMS19's role in NER and transcription.

Rad51 siRNA delivered by HVJ envelope vector enhances the anti-cancer effect of cisplatin

BACKGROUND

Every cancer therapy appears to be transiently effective for cancer regression, but cancers gradually transform to be resistant to the therapy. Cancers also develop machineries to resist chemotherapy. Short interfering RNA (siRNA) has been evaluated as an attractive and effective tool for suppressing a target protein by specifically digesting its mRNA. Suppression of the machineries using siRNA may enhance the sensitivity to chemotherapy in cancers when combined with an effective delivery system.

METHODS

To enhance the anti-cancer effect of chemotherapy, we transferred siRNA against Rad51 into various human cancer cells using the HVJ (hemagglutinating virus of Japan, Sendai virus) envelope vector in the presence or absence of cis-diamminedichloroplatinum(II) (CDDP, cisplatin). The inhibition of cell growth was assessed by a modified MTT assay, counting cell number, or fluorescence-activated cell sorting (FACS) analysis after Annexin V labeling. The synthetic Rad51 siRNA was also introduced into subcutaneous tumor masses of HeLa cells in SCID mice with or without intraperitoneal injection of CDDP, and tumor growth was monitored.

RESULTS

When synthetic Rad51 siRNA was delivered into HeLa cells using the HVJ envelope vector, no Rad51 transcripts were detected on day 2, and Rad51 protein completely disappeared for 4 days after siRNA transfer. When HeLa cells were incubated with 0.02 microg/ml CDDP for 3 h after siRNA transfer, the number of colonies decreased to approximately 10% of that with scrambled siRNA. The sensitivity to CDDP was enhanced in various human cancer cells, but not in normal human fibroblasts. When Rad51 siRNA was delivered into tumors using the HVJ envelope vector, the Rad51 transcript level was reduced to approximately 25%. Rad51 siRNA combined with CDDP significantly inhibited tumor growth when compared to siRNA or CDDP alone.

CONCLUSIONS

Rad51 siRNA could enhance the sensitivity to CDDP in cancer cells both in vitro and in vivo. Our results suggest that the combination of CDDP and Rad51 siRNA will be an effective anti-cancer protocol.

A phase I and pharmacokinetic study of VNP40101M, a new alkylating agent, in patients with advanced or metastatic cancer

PURPOSE

VNP40101M is a new alkylating agent that demonstrated broad anti-tumor activity in murine tumor models. A phase I trial was initiated to determine the toxicities, maximum tolerated dose, and pharmacokinetics of VNP40101M by short IV infusion.

STUDY DESIGN

The starting dose was 3 mg/m(2) every four weeks, and was escalated in successive cohorts as follows: 6, 12, 24, 40, 60, 80, and 100 mg/m(2). Beyond 100 mg/m(2), dose increments were 25%. Initially, 1-2 patients were assigned to a dose level. Intra-patient dose escalation was permitted. With the first instance of a drug-related > or = grade 2 adverse event, all dose levels required assessment of 3-6 patients. Pharmacokinetic parameters were assessed in the first cycle and any cycle with a change in dose.

RESULTS

Twenty-six patients in 13 dose levels ranging from 3-305 mg/m(2) were evaluated. Dose-related thrombocytopenia was the major toxicity, with the nadir occurring at a median of day 27. At 305 mg/m(2), six of eight patients developed grade 3 thrombocytopenia, including one event that met the definition for DLT. Other dose-related toxicities included moderate granulocytopenia, anemia, and a mild infusion-related syndrome consisting of acute headache and facial flushing. The granulocyte nadir occurred at a median of day 34, and recovery of both thrombocytopenia and neutropenia to < grade 2 occurred at a median of day 43. VNP40101M peak plasma concentrations and AUC were linear with dose. The elimination half-life was short and estimated to be approximately 15 minutes.

CONCLUSIONS

The MTD and recommended dose for phase II trials is 305 mg/m(2) every six weeks. Phase II trials in less heavily pre-treated patient populations are warranted.

Irofulven cytotoxicity depends on transcription-coupled nucleotide excision repair and is correlated with XPG expression in solid tumor cells

BACKGROUND

Irofulven is a novel alkylating agent with promising clinical activity, particularly toward ovarian and hormone-refractory prostate cancers. To facilitate additional clinical development, we have aimed to identify biological markers associated with sensitivity to the compound.

METHODS

Fibroblasts derived from patients with xeroderma pigmentosum or Cockayne's syndrome along with a panel of 20 human cancer cell lines (eight different tumor types) were examined to establish the importance of nucleotide excision repair proteins in the sensitivity to irofulven.

RESULTS

Human cells deficient in nucleotide excision repair are up to 30-fold more sensitive to the cytotoxic effects of irofulven compared with repair-proficient controls, clearly indicating that nucleotide excision repair plays a crucial role in the sensitivity to the drug. Interestingly, our results show that irofulven-induced lesions are recognized by transcription-coupled repair but not by global genome repair. Another unique feature is the pronounced sensitivity of XPD and XPB helicase-deficient cells to the drug. Comparison of the IC50 values for irofulven, cisplatin, and ecteinascidin 743 with the expression levels of ERCC1, XPD, and XPG genes in different solid tumor cell lines shows no correlation between the expression levels of any of the three nucleotide excision repair proteins and the sensitivity to ecteinascidin 743. In contrast, expression of the XPG endonuclease was correlated with the cytotoxicity for irofulven and, to a lesser degree, for cisplatin. Importantly, XPG expression was also correlated with cellular nucleotide excision repair activity.

CONCLUSIONS

Increasing evidence indicates that compromised nucleotide excision repair activity is frequent in several solid tumor types. The results presented here suggest that XPG expression in such tumors may be a useful marker to predict their sensitivity to irofulven.

Control of radiosensitivity of F9 mouse teratocarcinoma cells by regulation of histone H2AX gene expression using a tetracycline turn-off system

The mouse histone H2AX has unique COOH-terminal serine residues that are phosphorylated in response to double-strand DNA breaks introduced by ionizing radiation. This suggests that H2AX acts to maintain genomic stability. We constructed a tetracycline (tet)-directed turn-off vector and integrated it into F9 mouse teratocarcinoma cells by homologous recombination. In homozygously recombined cells, expression of the histone H2AX gene was repressed to 0.02% of the expression observed in wild-type cells by the addition of doxycycline, an analog of tet. Sensitivity of cells with repressed H2AX expression to X-irradiation was increased 1.95x, indicating that DNA repair was impaired by repression of H2AX. When we s.c. injected tet-regulated F9 cells into the flanks of mice, tumor growth was slightly suppressed by X-irradiation in H2AX-repressed tumors, whereas without X-irradiation, tumor growth did not differ by H2AX status. Thus, H2AX might be a potential molecular target for sensitizing cancer cells to radiotherapy to minimize required irradiation doses.

Update on NCI in vitro drug screen utilities

Development of new anti-cancer drugs is a costly and risky proposition. The Developmental Therapeutics Program (DTP) of the National Cancer Institutes of the United States (U.S.) facilitates the drug development process by providing access to preclinical screening services. Since the early 1990's, DTP has screened tens of thousands of compounds against a panel of 60 human tumour cell lines representing nine tissue sites. At the same time, DTP began to accumulate information on the expression of molecular entities in the same 60 cell line panel. Many of these data are freely available to the public at. More recently, additional, more focused screens have entered the picture, with data also available through the web site. These include screening of roughly 100000 compounds against a panel of yeast mutants, and screening of the NCI Diversity Set in assays designed to detect effects on Molecular Targets of interest.

A Phase I and Pharmacokinetic Study of VNP40101M, a Novel Sulfonylhydrazine Alkylating Agent, in Patients with Refractory Leukemia

PURPOSE

VNP40101M is a novel sulfonylhydrazine alkylating agent with broad antitumor activity in animal models. As alkylating agents are important antileukemia drugs, a Phase I and pharmacokinetic study of VNP40101M was conducted in patients with refractory or relapsed leukemias or poor-risk myelodysplastic syndromes (MDS).

EXPERIMENTAL DESIGN

VNP40101M was given as a single i.v. infusion over 15-70 min on day 1. Courses were repeated every 4 weeks according to antileukemic activity. The starting dose of 220 mg/m(2) was escalated by approximately 33% in cohorts of 3-6 patients until a maximum-tolerated dose was established. One additional cohort was treated with the maximum-tolerated dose divided over days 1 and 8.

RESULTS

Thirty-eight patients, including 28 with acute myeloid leukemia and 5 with MDS, received 52 courses of treatment. Nondose-limiting, reversible infusion-related toxicities were the most frequent adverse event, occurring in 24 (63%) patients on the first course. Dose escalation was terminated at 708 mg/m(2) for prolonged myelosuppression in 1 of 7 patients, and 600 mg/m(2) was selected as the recommended Phase II dose, with no significant extramedullary toxicity at this dose level. Two patients, 1 with MDS treated with 300 mg/m(2) and 1 with acute myeloid leukemia treated with 600 mg/m(2), achieved complete remission.

CONCLUSIONS

VNP40101M had significant antileukemic activity and minimal extramedullary toxicity in patients with relapsed or refractory disease.

Xeroderma pigmentosum group a protein and chemotherapy resistance in human germ cell tumors

The exceptional sensitivity of germ cell tumors (GCTs) of adolescents and adults to chemotherapy, in particular to cisplatin, has been attributed to low levels of xeroderma pigmentosum group A protein (XPA), a crucial component of the nucleotide excision repair DNA repair pathway. In different types of solid tumors, resistance to cisplatin has been associated with enhanced expression of XPA. To assess the role of XPA levels in clinical sensitivity and resistance of GCTs to chemotherapy, immunohistochemistry was performed on tumor samples of both unselected patients before therapy and patients with fully documented clinical course before and after therapy. In the case of high XPA levels, fluorescent in situ hybridization was applied to assess the possibility of gene amplification. XPA protein levels were investigated by Western blot analysis after repeated exposure to cisplatin in different GCT-derived cell lines. Finally, XPA levels of both sensitive and cisplatin-resistant GCT cell lines were compared with cell lines derived from other neoplasms. We found that the presence of XPA protein as assessed by immunohistochemistry differs among the various histologies of GCTs. It is found more frequently and with a more homogenous staining pattern in histologic subtypes showing a more differentiated phenotype. Overall, no differences in the presence of XPA was observed between samples of tumors refractory or sensitive to chemotherapy. No XPA gene amplification was found. Interestingly, all tumors resected in relapse after chemotherapy in the refractory group stained positive for XPA. However, XPA was not induced by repeated courses of sublethal doses of cisplatin in GCT-derived cell lines in vitro, and no correlation between XPA protein levels and sensitivity to cisplatin in three GCT-derived cell lines was observed. We therefore conclude that XPA does not play a critical role in overall treatment resistance of GCTs.