ERCC1 Protein Research Articles

Association between ERCC1 and XPA expression and polymorphisms and the response to cisplatin in patients with non-seminomatous testicular germ cell tumors.

4555 Background: Cisplatin-based chemotherapy cures over 80% of testicular germ cell tumors (TGCTs); nucleotide-excision repair (NER) modifies the sensitivity to cisplatin. In this work we explored the association between NER-proteins and their polymorphisms (SNPs) with cisplatin-sensitivity (CPS) and overall survival (OS) of patients with advanced non-seminomatous (ns)-TGCTs treated with bleomycin-etoposide-cisplatin (BEP). Methods: ERCC1, XPA-expression and gammaH2AX-presence, were tested in cisplatin-treated cancer cell lines. ERCC1 and XPA-expression were also analyzed in ns-TGCTs by qPCR. Immunohistochemistry was performed to detect ERCC1 protein in ns-TGCTs specimens. The SNPs were genotyped by PCR-RFLPs technique. Results: High basal ERCC1-expression was observed in non-CPS cancer cell lines; ERCC1-expression augmented further, as well as gammaH2AX, after cisplatin-treatment. Basal ERCC1 expression increases in the non-CPS patients in Mexican and Peruvian populations compared to CPS patients (p<0.001; p=0.002). XPAexpression levels weren’t different. These polymorphisms weren’t associated with CPS or OS. ERCC1-positive immunostaining was observed in 30/108 patients (27.8%). From 76 patients that were CPS, 59 (77.6%) were ERCC1-negative, compared with 17 (22.4%) that were ERCC1-positive (p=0.05). 5-year OS probability was smaller for those patients ERCC1-positive and non-CPS (15.38%) than tumor ERCC1-negative and CPS (89.3%) (p<0.001). Using the Cox Model, adjusted on the prognosis groups, the hazard ratio (HR) of death in patients with ERCC1-negative and non-CPS was >14.43 and in patients ERCC1-positive and non-CPS the HR was >11.86 (p<0.001). Conclusions: High-levels of ERCC1-expression and ERCC1-protein are associated with non-CPS, suggesting the use of ERCC1 as a potential indicator of response to cisplatin-based chemotherapy and the prognosis in patients with ns-TGCTs. Moreover, it’s important to identify patients potentially non-CPS in order to diminish the toxicity of cisplatin and improved quality of life avoiding adverse effects due to this agent. Work supported by CONACYT 83959 and PAPIIT IN213311-3.

Randomized International Phase III Trial of ERCC1 and RRM1 Expression–Based Chemotherapy Versus Gemcitabine/Carboplatin in Advanced Non–Small-Cell Lung Cancer

We assessed whether chemotherapy selection based on in situ ERCC1 and RRM1 protein levels would improve survival in patients with advanced non-small-cell lung cancer (NSCLC). Eligible patients were randomly assigned 2:1 to the trial's experimental arm, which consisted of gemcitabine/carboplatin if RRM1 and ERCC1 were low, docetaxel/carboplatin if RRM1 was high and ERCC1 was low, gemcitabine/docetaxel if RRM1 was low and ERCC1 was high, and docetaxel/vinorelbine if both were high. In the control arm, patients received gemcitabine/carboplatin. The trial was powered for a 32% improvement in 6-month progression-free survival (PFS). Of 331 patients registered, 275 were eligible. The median number of cycles given was four in both arms. A tumor rebiopsy specifically for expression analysis was required in 17% of patients. The median time from informed consent to expression analysis was 11 days. We found no statistically significant differences between the experimental arm and the control arm in PFS (6.1 months v 6.9 months) or overall survival (11.0 months v 11.3 months). A subset analysis revealed that patients with low levels for both proteins who received the same treatment in both treatment arms had a statistically better PFS (P = .02) in the control arm (8.1 months) compared with the experimental arm (5.0 months). This demonstrates that protein expression analysis for therapeutic decision making is feasible in newly diagnosed patients with advanced-stage NSCLC. A tumor rebiopsy is safe, required in 17%, and acceptable to 89% (47 of 53) of patients.

Phase II study of neoadjuvant dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin (ddMVAC) chemotherapy in patients with muscle-invasive urothelial cancer (MI-UC): Pathologic and radiologic response, serum tumor markers, and DNA excision repair pathway biomarkers in relation to disease-free survival (DFS).

4530 Background: Neoadjuvant (NA) ddMVAC in patients (pts) with MI-UC is associated with significant pathologic response (PaR) and radiologic response (RaR). We examined the frequency of PaR and RaR as well as the level of serum and tissue biomarkers in correlation with DFS. Methods: Pts treated on phase II prospective study of NA ddMVAC (4 cycles) in MI-UC were evaluated for RaR (at least >50% decrease in the primary tumor and nodes after chemotherapy, with delayed enhancement of residual disease) and PaR (p<T1N0M0). Elevated serum tumor markers (CA125, C19-9 and ßHCG) at baseline and Day 1 of each cycle were documented. Expression level of baseline DNA ERCC1 protein in tumor biopsy tissues was determined by immunohistochemistry based on H-score <0.1 (negative) vs. >0.1 (positive). Fisher’s Exact test was used to evaluate association with response. Post-surgery DFS was estimated by the Kaplan-Meier method and compared between response and biomarker groups using the logrank test. Results: Of 39 pts (cT2:42%, cT3:42%, cT4:16%, and cN1:45%), 49% (90% CI 35-63) experienced PaR, and 62% (90% CI 47-75) achieved RaR after ddMVAC chemotherapy. Pts who achieved PaR experienced a DFS advantage, with 18-month DFS of 78% (95% CI 47-92) vs. 48% (95% CI 18-74) in those who did not (p=0.146). Those achieving RaR had a significantly longer DFS (p=0.006), with 18-month DFS of 87% (95% CI 57-97) vs. 29% (95% CI 5-60) in those who did not. Among 10 pts with any elevated serum tumor marker at baseline, only 2 pts showed normalization, both without a PaR. ERCC1(+) tumors were not associated with PaR, pT0 or RaR. DFS by ERCC1status was inconclusive due to limited sample size. 18-month DFS was 91% (95% CI 51-99) in ERCC1(+) tumors vs. 63% (95% CI 29-85) in ERCC1(-) tumors. Conclusions: ddMVAC achieves significant PaR and RaR in MI-UC pts that translates into a post-surgery DFS advantage. ERCC1(+) was not associated with response. More effective biomarkers of platinum response are needed to select pts most likely to benefit from NA therapy. Clinical trial information: NCT00808639.

MSH3 expression does not influence the sensitivity of colon cancer HCT116 cell line to oxaliplatin and poly(ADP-ribose) polymerase (PARP) inhibitor as monotherapy or in combination

Defective expression of the mismatch repair protein MSH3 is frequently detected in colon cancer, and down-regulation of its expression was found to decrease sensitivity to platinum compounds or poly(ADP-ribose) polymerase inhibitors (PARPi) monotherapy. We have investigated whether MSH3 transfection in MSH3-deficient colon cancer cells confers resistance to oxaliplatin or PARPi and whether their combination restores chemosensitivity. MSH3-deficient/MLH1-proficient colon cancer HCT116(MLH1) cells were transfected with the MSH3 cDNA cloned into the pcDNA3.1(-) vector. MSH3/MLH1-deficient HCT116, carrying MLH1 and MSH3 mutations on chromosome 3 and 5, respectively, and HCT116 in which wild-type MLH1 (HCT116+3), MSH3 (HCT116+5) or both genes (HCT116+3+5) were introduced by chromosome transfer were also tested. Sensitivity to oxaliplatin and to PARPi was evaluated by analysis of clonogenic survival, cell proliferation, apoptosis and cell cycle. MSH3 transfection in HCT116 cells did not confer resistance to oxaliplatin or PARPi monotherapy. MSH3-proficient HCT116+5 or HCT116+3+5 cells, which were more resistant to oxaliplatin and PARPi in comparison with their MSH3-deficient counterparts, expressed higher levels of the nucleotide excision repair ERCC1 and XPF proteins, involved in the resistance to platinum compounds, and lower PARP-1 levels. In all cases, PARPi increased sensitivity to oxaliplatin. Restoring of MSH3 expression by cDNA transfection, rather than by chromosome transfer, did not affect colon cancer sensitivity to oxaliplatin or PARPi monotherapy; PARP-1 levels seemed to be more crucial for the outcome of PARPi monotherapy.

Abstract 1301: Metformin induces cytotoxicity by TP and ERCC1 decrease.

Abstract Metformin is an anti-diabetic drug recently shown to inhibit cancer cell proliferation and growth, although the involved molecular mechanisms have not been elucidated. In many cancer cells, highly expression of thymidine phosphorylase (TP) and ERCC1 are associated with poor prognosis. We used A549 and H1975 huamn non-small cell lung cancer (NSCLC) cell lines to investigate the role of TP and ERCC1 expression in metformin-induced cytotoxicity. Metformin treatment decreased cellular TP and ERCC1 protein and mRNA levels by down-regulating phosphorylated MEK1/2-ERK1/2 protein levels in a dose- and time-dependent manner. The enforced expression of the constitutively active MEK1 (MEK1-CA) vectors significantly restored cellular TP and ERCC1 protein levels and cells viability. Specific inhibition of TP and ERCC1 expression by siRNA enhanced the metformin-induced cytotoxicity and growth inhibition. In conclusion, metformin induces cytotoxicity by down-regulating TP and ERCC1 expression in NSCLC cells. Citation Format: Yun-Wei Lin, Yu-Ching Huang, Sheng-Chieh Tseng, Hsien-Chun Chiu, Huang-Jen Chen, Yi-Jhen Huang, Ting-Yu Wo, Shao-Hsing Weng, Jen-Chung Ko. Metformin induces cytotoxicity by TP and ERCC1 decrease. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1301. doi:10.1158/1538-7445.AM2013-1301

Abstract 630: ERCC1-202 isoform is responsible for all known functions of ERCC1.

Abstract Background: ERCC1 is a DNA repair protein whose expression is a prognostic and predictive biomarker of chemotherapy effect in NSCLC. Four alternative transcripts of the ERCC1 gene have been described (isoforms 201 to 204). We previously found that only ERCC1-202 isoform is able to remove cisplatin-DNA adducts and to improve survival after cisplatin treatment. Little is known however about the role of the other isoforms. Since the four isoforms are expressed in human samples, we sought to elucidate the contribution of these different ERCC1-isoforms to ERCC1 described functions within and beyond DNA repair. Methods: We used an established ERCC1-deficient A549 cells with selective re-expression of each ERCC1 isoform. We searched for negative dominant functions of the ERCC1-201, -203, and -204 isoforms using proliferation assay (WST-1) and clonogenic assay. Respective cellular localizations of the isoforms were assessed by immunofluorescent (IF) staining and interacting abilities with previously identified ERCC1 partners was estimated by proximity ligation assays (Duolink). We finally investigated their influence on the cellular mitotic process (mitotic spindle shape) by alpha- and gamma-tubulin IF and video microscopy. Results: IF detection of ERCC1 protein isoforms revealed a nuclear localization of ERCC1-201 and -202 isoforms whereas ERCC1-203 and -204 isoforms were mainly detected in the cytoplasm. This alternative cellular localization suggests alternative roles for ERCC1-203 and -204. Only ERCC1-202 formed a stable heterodimer complex with XPF and other interacting partners (XPA, MSH2, FANCG, SLX4 and TRF2). None of the isoforms decreased cisplatin resistance (IC50) associated with ERCC1-202 expression. Interstrand Cross-Link repair (ICL-R) efficiency (mitomycin-C treatment) was also exclusively rescued with ERCC1-202 re-expression. Further, ERCC1 deficient cells displayed mitotic aberrations such as chromosome bridges at anaphase that impaired cytokinesis and generated aneuploidy. Only ERCC1-202 isoform restored chromosome segregation accuracy. Conclusions: Alternative roles for ERCC1 beyond the canonical NER pathway are currently emerging. Our data suggest that all currently known functions of ERCC1 are fulfilled by the same ERCC1 isoform ERCC1-202. Despite their wide expression in human samples, the identification of alternative roles of other isoforms is still under investigation. Our A549 clones, with stable ERCC1 deficiency, provide a promising tool to analyze different functions of ERCC1. Finally, most antibodies used to test ERCC1 status in patients do not distinguish between different isoforms, it is important to develop an antibody (or alternative diagnostic method) able to specifically recognize only the functional ERCC1-202 isoform. Given that ERCC1-202/XPF interaction domains can be produced together it would be realistic to use it as an immunogenic epitope and/or a therapeutic target. Citation Format: Luc Friboulet, Ken André Olaussen, Florence Ponsonnailles, Annabelle Stoclin, Nicolas Dorvault, Julien Adam, Frédéric Commo, Patrick Saulnier, Fabrice André, Jean-Charles Soria. ERCC1-202 isoform is responsible for all known functions of ERCC1. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 630. doi:10.1158/1538-7445.AM2013-630

Small Molecule Inhibitors of ERCC1-XPF Protein-Protein Interaction Synergize Alkylating Agents in Cancer Cells

The benefit of cancer chemotherapy based on alkylating agents is limited because of the action of DNA repair enzymes, which mitigate the damage induced by these agents. The interaction between the proteins ERCC1 and XPF involves two major components of the nucleotide excision repair pathway. Here, novel inhibitors of this interaction were identified by virtual screening based on available structures with use of the National Cancer Institute diversity set and a panel of DrugBank small molecules. Subsequently, experimental validation of the in silico screening was undertaken. Top hits were evaluated on A549 and HCT116 cancer cells. In particular, the compound labeled NSC 130813 [4-[(6-chloro-2-methoxy-9-acridinyl)amino]-2-[(4-methyl-1-piperazinyl)methyl]] was shown to act synergistically with cisplatin and mitomycin C; to increase UVC-mediated cytotoxicity; to modify DNA repair as indicated by the staining of phosphorylated H2AX; and to disrupt interaction between ERCC1 and XPF in cells. In addition, using the Biacore technique, we showed that this compound interacts with the domain of XPF responsible for interaction with ERCC1. This study shows that small molecules targeting the protein-protein interaction of ERCC1 and XPF can be developed to enhance the effects of alkylating agents on cancer cells.

Induction of apoptosis and suppression of ERCC1 expression by the potent amonafide analogue 8-c in human colorectal carcinoma cells

Previous studies have reported that 8-c [6-(2-(2-(dimethylamino)ethylamino)ethylamino)-2-octyl-1H-benzo[de]isoquinoline-1,3(2H)-dione], a novel amonafide analogue, was generated as a new anticancer candidate. However, little is known about its activity in chemoresistant cells. In this study, the antitumor effects of 8-c on the multi-drug-resistant human colorectal carcinoma cancer cell lines HCT-116/L-OHP and HCT-8/VCR have been investigated for the first time. 8-c showed similar concentration-dependent inhibitory activities against multi-drug-resistant cells and corresponding parental cell lines by the MTT assay after 48 h of treatment. 8-c treatment resulted in the induction of apoptosis, as evidenced by fluorescent staining analysis, comet assay data, and the increase in the number of apoptotic cells as detected by flow cytometry. Western blot, qPCR, and siRNA techniques were used to elucidate the molecular mechanism. Our study suggested that the apoptotic effect of 8-c can be attributed to the upregulation of p53, caspase-3, and cleaved poly(ADP-ribose) polymerase (PARP) and the downregulation of Bcl-2. Furthermore, ERCC1 is essential for nucleotide excision repair. ERCC1 expression was correlated with sensitivity to chemotherapy in various colon cancer cell lines. It is intriguing that decreases in ERCC1 protein and mRNA levels were also observed in the HCT-116/L-OHP and HCT-8/VCR cells after exposure to 8-c. Further transient transfection of multi-drug-resistant cells with ERCC1 siRNA enhanced 8-c-induced cytotoxicity. In contrast, epidermal growth factor-induced increase in ERCC1 protein levels was shown to rescue cell viability upon 8-c treatment. These findings suggest that 8-c has a strong potential to be developed as a new antitumor agent for the treatment of multi-drug-resistant colon cancer cells, and is worthy of further studies.

Relationship of ERCC1 genotype variant with mRNA expression and ERCC1 protein levels in advanced urothelial carcinoma (UC).

260 Background: DNA repair factors may be predictive for response to chemotherapies that produce DNA damage. While low ERCC1 protein and mRNA levels have been reported as associated with improved outcomes in metastatic UC patients treated with platinum-based chemotherapy, the relationship between genotype, mRNA expression, and protein level is unknown. The ERCC1 germline 19007C>T single-nucleotide polymorphism (SNP) is functionally associated with reduced translation of ERCC1 mRNA. We investigated the relationship between ERCC1 germline SNP, ERCC1 tumor mRNA and protein expression, in a cohort of patients with advanced UC who received first-line, platinum-based chemotherapy. Methods: A cohort of clinically annotated, uniformly-treated advanced UC patients with FFPE primary tumor tissue available was identified through the Hellenic cooperative Oncology Group (HECOG) (N=93). Genomic DNA extraction, nested PCR, and restriction fragment length polymorphism techniques for the 19007C>T SNP were performed to identify C/C, C/T and T/T genotypes. ERCC1 mRNA expression was interrogated using Nanostring nCounter profiling. IHC analysis was performed on tissue arrays using an ERCC1 antibody. Percent of positive nuclear staining was categorized as quartiles using previously identified cut-points. Results: ERCC1 C/T genotype was identified in 30/61 samples (49%) and T/T in 14/61 samples (23%). In 54 patients with both SNP and mRNA data available, T/T genotype was associated with the highest level of mRNA expression, followed by the C/T genotype (p=0.04). Neither ERCC1 genotype (N=44) nor ERCC1 mRNA expression (N=54) was associated with ERCC1 protein expression as measured by IHC (p=0.52 and p=0.13, respectively). Conclusions: ERCC1 19007C>T is associated with increased ERCC1 mRNA expression. However, neither genotype nor mRNA are surrogates for ERCC1 protein detected by IHC in advanced UC tumors. This suggests that while genotype influences mRNA expression of ERCC1, the use of the nucleotide excision repair pathway as a predictive biomarker of platinum-sensitivity may be more complex than previously appreciated and require the integrative use of proteomics, genomics and epigenomics.

Assessment of ERCC1 and XPF Protein Expression Using Quantitative Immunohistochemistry in Nasopharyngeal Carcinoma Patients Undergoing Curative Intent Treatment

We sought to evaluate the prognostic/predictive value of ERCC1 and XPF in patients with nonmetastatic nasopharyngeal carcinoma (NPC) treated with curative intent. ERCC1 and XPF protein expression was evaluated by immunofluorescence combined with automated quantitative analysis (AQUA) using the FL297 and 3F2 antibodies, respectively. ERCC1 and XPF protein expression levels were correlated with clinical outcomes. Patient characteristics were as follows: mean age 52 years (range, 18-85 years), 67% male, 72% Karnofsky performance status (KPS) ≥ 90%, World Health Organization (WHO) type 1/2/3 = 12%/28%/60%, stage III/IV 65%. With a median follow-up time of 50 months (range, 2.9 to 120 months), the 5-year overall survival (OS) was 70.8%. Median standardized nuclear AQUA scores were used as cutpoints for ERCC1 (n=138) and XPF (n=130) protein expression. Agreement between dichotomized ERCC1 and XPF scores was high at 79.4% (kappa = 0.587, P<.001). Neither biomarker predicted locoregional recurrence, DFS, or OS after adjustment for age and KPS, irrespective of stratification by stage, WHO type, or treatment. Neither ERCC1 nor XPF, analyzed by quantitative immunohistochemistry using the FL297 and 3F2 antibodies, was prognostic or predictive in this cohort of NPC patients.

Using protein microarray technology to screen anti-ERCC1 monoclonal antibodies for specificity and applications in pathology

BackgroundAn antibody with cross-reactivity can create unexpected side effects or false diagnostic reports if used for clinical purposes. ERCC1 is being explored as a predictive diagnostic biomarker for cisplatin-based chemotherapy. High ERCC1 expression is linked to drug resistance on cisplatin-based chemotherapy. 8F1 is one of the most commonly used monoclonal antibodies for evaluating ERCC1 expression levels in lung cancer patient tissues, but it has been noted that this antibody cross-reacts with an unknown protein.ResultsBy using a high density protein microarray chip technology, we discovered that 8F1 not only reacts with its authentic target, ERCC1, but also cross-reacts with an unrelated nuclear membrane protein, PCYT1A. The cross-reactivity is due to a common epitope presented on these two unrelated proteins. Similar to the subcellular localization of ERCC1, IHC tests demonstrated that PCYT1A is localized mainly on nuclear membrane. In this study, we also discovered that the PCYT1A gene expression level is significantly higher than the ERCC1 gene expression level in a certain population of lung cancer patient tissue samples. To develop the best monoclonal antibody for ERCC1 IHC analysis, 18 monoclonal antibodies were generated and 6 of them were screened against our protein microarray chip. Two clones showed high mono-specificity on the protein microarray chip test and both worked for the IHC application.ConclusionIn summary, the 8F1 clone is not suitable for ERCC1 IHC assay due to its cross-reactivity with PCYT1A protein. Two newly generated monoclonal antibodies, 4F9 and 2E12, demonstrated ultra-specificity against ERCC1 protein and superior performance for IHC analyses.

Emodin affects ERCC1 expression in breast cancer cells

BackgroundMulti-drug resistance to chemotherapeutic agents is a major cause of treatment failure in breast cancer. In this study, we investigated the effects of emodin on reversing the multi-drug resistance, examined the ERCC1 protein expression in breast cancer cell line, and explored the relationship between reversal of multi-drug resistance and ERCC1 protein expression.MethodsMTT assay was conducted to test the cytotoxicity of adriamycin and cisplatin to MCF-7/Adr cells with and without emodin pretreatment, and Western blot was performed to examine the ERCC1 protein expression.ResultsMCF-7/Adr cells had 21-fold and 11-fold baseline resistances to adriamycin and cisplatin, respectively. When emodin was added to the cell culture at the concentration of 10 μg/ml, the drug resistance was reduced from 21 folds to 2.86 folds for adriamycin, and from 11 folds to 1.79 folds for cisplatin. MCF-7/Adr cells treated with two concentrations (10μg/mL and 20μg/mL) of emodin, after 2, 4, 6, 10 days, the trend of ERCC1 expression was gradually decreased and the reduction was more obvious comparatively at the concentration of 20μg/mL.ConclusionsEmodin could reverse the multi-drug resistance in MCF-7/Adr cells and down-regulate ERCC1 protein expression.

DNA repair endonuclease ERCC1-XPF as a novel therapeutic target to overcome chemoresistance in cancer therapy

The ERCC1–XPF complex is a structure-specific endonuclease essential for the repair of DNA damage by the nucleotide excision repair pathway. It is also involved in other key cellular processes, including DNA interstrand crosslink (ICL) repair and DNA double-strand break (DSB) repair. New evidence has recently emerged, increasing our understanding of its requirement in these additional roles. In this review, we focus on the protein–protein and protein–DNA interactions made by the ERCC1 and XPF proteins and discuss how these coordinate ERCC1–XPF in its various roles. In a number of different cancers, high expression of ERCC1 has been linked to a poor response to platinum-based chemotherapy. We discuss prospects for the development of DNA repair inhibitors that target the activity, stability or protein interactions of the ERCC1–XPF complex as a novel therapeutic strategy to overcome chemoresistance.

Expression of ERCC1 protein (excision repair cross complementing group 1) in patients with invasive carcinoma of the uterine cervix (CC) undergoing definitive chemoradiation (CR).

e15562 Background: CC is the leading cause of cancer death among women in developing countries. ERCC1 protein participates in DNA repair through the nucleotide excision repair pathway, involved in resistance to platinum-based chemotherapy. Its value as a predictive marker of tumor response to treatment, progression or death is still unknown. We evaluated ERCC1 protein expression and clinical variables as a predictive marker of progression-free survival (PFS) and overall survival (OS) in patients (pts) with CC submitted to CR. Methods: Retrospective data analysis of pts with histological diagnosis of CC, treated with CR between 2004-2009. Platinum-based chemotherapy was administered weekly (x6) concurrent to external beam radiotherapy (EBRT) to the pelvis (39.6 – 45.0 Gy), parametrial boost (14.0 – 20.0 Gy) when indicated and high-dose rate brachytherapy (HDR) (28.0 – 30.0 Gy). ERCC1 expression was assessed by immunohistochemistry (IHC). Results: We analyzed 75 pts, median age was 55 years (range 24-76), the performance status (PS) was 0 or 1 at baseline in 50 pts (66%) and 63 had squamous histology (84%). Thirty-two were stage IIB (43%) and 19 were IIIB (25%). Sixty-five patients received cisplatin 40mg/m2/w (87%) and 9, carboplatin AUC2/w (12%), median of 6 cycles (range 2-9). Median RT and HDR doses were 59.4 Gy (range 40.4 to 60.3) and 28.0 Gy (range 14.0 – 37.5), respectively. Thirty-two pts were available by ERCC1 IHC and all expressed the marker. Median PFS and OS were 35.5 (95% CI – 13.8 - 57.6) and 81 (95% CI- 21.2 - 140.8) months, respectively. In multivariate analysis, receiving &lt; 6 chemotherapy cycles and baseline Hb &lt;10.0 were correlated with disease progression and death, HR 0.302; p 0.011 (95% CI- 0.012-0.762) and HR 0.6; p 0.00 (95% CI- 0.474 – 0.760), respectively. PS at baseline did not correlate with PFS or OS, HR 0.985; p 0.614 (95% CI 0.930 – 1.044). Conclusions: In this population, since all pts expressed the protein, ERCC1 expression couldn't discriminate patients who most benefit from CR. Interestingly, a minimum of 6 chemotherapy cycles and a baseline Hb ≥ 10.0 seem to have a prognostic value.

Comparison of ERCC1/XPF genetic variation, mRNA and protein levels in women with advanced stage ovarian cancer treated with intraperitoneal platinum

ObjectiveApproximately 20% of patients receiving platinum-based chemotherapy for epithelial ovarian cancer (EOC) are refractory or develop early recurrence. Identifying these patients early could reduce treatment-associated morbidity and allow quicker transfer to more effective therapies. Much attention has focused on ERCC1 as a potential predictor of response to therapy because of its essential role in the repair of platinum-induced DNA damage. The purpose of this study was to accurately measure protein levels of ERCC1 and its essential binding partner XPF from patients with EOC treated with platinum-based therapy and determine if protein levels correlate with mRNA levels, patient genotypes or clinical outcomes. MethodsERCC1 and XPF mRNA and protein levels were measured in frozen EOC specimens from 41 patients receiving intraperitoneal platinum-based chemotherapy using reverse transcription polymerase chain reaction and western blots. Genotypes of common nucleotide polymorphisms were also analyzed. Patient outcomes included progression free (PFS) and overall survival (OS). ResultsExpression of ERCC1 and XPF were tightly correlated with one another at both the mRNA and protein level. However, the mRNA and protein levels of ERCC1 were not positively correlated. Likewise, none of the SNPs analyzed correlated with ERCC1 or XPF protein levels. There was an inverse correlation between mRNA levels and patient outcomes. ConclusionNeither genotype nor mRNA levels are predictive of protein expression. Despite this, low ERCC1 mRNA significantly correlated with improved PFS and OS.

Co-expression of ERCC1 and Snail is a prognostic but not predictive factor of cisplatin-based neoadjuvant chemotherapy for bladder cancer

Neoadjuvant chemotherapy (NC) for bladder cancer has been reported to significantly improve the 5-year survival rate. The aim of the present study was to examine the roles of ERCC1 and Snail in determining the response to chemotherapy in bladder cancer treated with NC and radical cystectomy (RC). The expression of the Snail and ERCC1 proteins was determined by immunohistochemical staining of specimens obtained from 58 patients with bladder tumors treated with NC and RC. The correlation between clinical response and the expression of Snail and ERCC1 was investigated. Snail and ERCC1 were co-expressed in 24 (41.4%) of the 58 patients. A marked correlation was found between the expression of Snail and ERCC1 (P=0.001). The co-expression of Snail and ERCC1 was not able to predict pathological complete response (P=0.202). Results of the univariate analysis revealed that the co-expression of Snail and ERCC1 predicted shorter disease-free survival (DFS) and overall survival (OS) than the negative expression of Snail and/or ERCC1. Moreover, the co-expression of ERCC1 and Snail was the only predictive factor for both DFS (P=0.029) and OS (P=0.040). The expression of Snail was correlated with that of ERCC1 and the co-expression of Snail and ERCC1 was the only significant predictive factor of shorter DFS and OS in patients with bladder cancer treated with NC and RC.

Abstract 4682: Compensatory activation of alternative DNA repair pathways following exposure to the PARP Inhibitor ABT-888 in vitro and in patients with solid malignancies

Abstract PARP inhibitors are being developed with the hope of inhibiting base excision repair in tumor cells following DNA insult. They do so by inhibiting poly ADP-ribose polymerase-1(PARP-1) which plays an important role in the repair of single-stranded DNA (ssDNA) breaks. Although some PARP inhibitors have been shown to suppress its target at safely achievable concentrations in humans, mono-therapy with these agents is generally not able to induce responses. The compensatory effect of alternative repair pathways, including., homologous recombination (HR) repair, nucleotide excision repair (NER), among others, could potentially be responsible for this lack of effect. Examples of HR repair proteins include those involved in the Fanconi Anemia/BRCA pathway and for NER, the ERCC proteins. We performed Western immunoblot analysis to evaluate the expression level of PAR, Fanconi Anemia D2, ERCC1 and beta-actin proteins in the human cancer cell lines H1299 (lung) and MDA-MB-231(breast) following exposure to the PARP inhibitor ABT-888 (veliparib). The expression level of these protein was also evaluated in human peripheral blood mononuclear cells (PBMCs) obtained from consenting patients with advanced solid malignancies participating in a dose escalation trial with ABT-888, as monotherapy or in combination with mitomycin C. PAR protein level was reduced at 6 hours post ABT-888 exposure (5μM) and maintained at low levels through 48 hours in the H1299 and MDA-MB-231cancer cells. However FANCD2 and ERCC1 protein expression was elevated simultaneously in these cancer cells post ABT-888. Similarly, FANCD2 and ERCC1 protein levels increased in the PBMCs of 22 patients analyzed following ABT-888 as a single agent (n=12) or in combination with mitomycin C (n=10). These results confirm that ABT888 can inhibit its target PAR expression both in cancer cells and patients’ PBMCs. However, our results also show that ABT-888 up-regulates homologous recombination (HR) and nucleotide excision repair (NER) pathways, which have the potential of resulting in not only resistance to the antitumor effect of ABT-888, but also in decreasing the effect of DNA targeting cytotoxic chemotherapy when combined with isolated PARP inhibition. It is plausible that cancers with defective FA or NER pathways, which are incapable of mounting a compensatory response, would represent a better target for ABT-888 alone or in combination with DNA targeted cytotoxic chemotherapy. Experiments aimed to evaluate this notion are underway. The potential role of other compensatory repair mechanisms also merit further investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4682. doi:1538-7445.AM2012-4682

Abstract 3120: Functional characterization of ERCC1 isoforms in NSCLC

Abstract Background: ERCC1 is a DNA repair protein whose expression is a prognostic and predictive biomarker of chemotherapy effect in NSCLC. Five alternative transcripts of the ERCC1 gene have been described or hypothesized to exist (isoforms 201 to 205). Nevertheless, little is known about the function and relative expression of these isoforms. We explored 3 main questions: a- Which ERCC1 isoforms are detected by clinically validated antibodies? b- Which isoforms are expressed in lung cancer cell lines and patient samples? c- Which isoforms are functional for removal of cisplatin DNA-adducts and potentially relevant as predictors of cisplatin resistance? Methods: To determine the specificity of anti-ERCC1 antibodies, a screening of isoform specific peptide sequences was achieved using a peptide array (Epitope Mapping CelluSpots™). The expression of ERCC1 isoforms was evaluated in 20 lung cancer cell lines and in 123 NSCLC patients by qRT-PCR. We established a functional DNA repair assay by monitoring the accumulation of cisplatin adducts over time with a specific antibody RC-18 (courtesy of Juergen Thomale, Germany). To investigate isoforms functionality, we created stable ERCC1 attenuated A549 cells with Zinc Finger Nucleases technology (Sigma). Using lentiviral constructs we rescued ERCC1 isoforms expression. Results: The 2 monoclonal antibodies, clone 8F1 and 3H11 recognize a conserved region shared by all isoforms of ERCC1 protein, and so, are unable to distinguish the different isoforms. The 5 isoforms were all detected at mRNA level, both in cancer cell lines and in patient tissues. Interestingly, a significant increase in isoform 201 expression was observed in all tumor tissues compared to normal counterparts. We obtained 7 A549 clones harboring a 85-95% decrease in ERCC1 expression. In these cells we observed a 7-fold increase in IC50 of cisplatin accompanied by a significant decrease in the rate of nucleotide excision repair (NER). We are currently exploring isoform function by analyzing DNA repair efficiency in the different stable cell lines. Conclusions: Alternative roles for ERCC1 beyond NER are currently emerging. Our 7 A549 clones, with stable and strong ERCC1 attenuation, provide a very promising tool to analyse all functions of ERCC1. Since most antibodies used to test ERCC1 positivity in patients do not distinguish the different isoforms, it is urgent to characterize their function further, particularly the role of isoform 201 overexpression in NSCLC tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3120. doi:1538-7445.AM2012-3120

Abstract 1766: Persistence of drug-induced DNA interstrand cross-links distinguishes bendamustine from conventional DNA cross-linking agents

Abstract Bendamustine has demonstrated substantial clinical efficacy in the treatment of hematologic malignancies and continues to distinguish itself from other alkylating agents. The mechanistic and clinical differences associated with bendamustine may be directly related to its unique structural features, although the precise mechanism of action is still poorly understood. We have undertaken a detailed study of the drug-DNA interactions of bendamustine. It alkylates DNA primarily at guanine-N7 positions with a sequence selectivity similar to other nitrogen mustards. It produces DNA interstrand cross-links (ICLs) in both solid tumor and hematological tumor cells at doses that cause growth inhibition. ICLs peak at 8h following a 1h treatment and persist over 48h in tumor cells including those that are proficient at repairing (unhooking) ICLs formed by melphalan or cisplatin. This persistence of ICLs is also observed in multiple myeloma cells from patients who have relapsed on melphalan therapy and which efficiently repair melphalan-induced ICLs compared to cells from treatment naive patients. The peak γ-H2AX response follows the ICL peak and also persists beyond 48h. Cells defective in ICL unhooking proteins ERCC1 and XPF, or defective in homologous recombination repair, show increased sensitivity to bendamustine, but at a level less than observed for other nitrogen mustards or cisplatin. Real time PCR profiling showed that at equivalent peak levels of DNA ICLs bendamustine induced fewer changes in DNA damage signaling and DNA repair gene expression compared to either cisplatin or melphalan. These data suggest that the critical DNA damage produced by bendamustine induces a different signaling and repair response to conventional cross-linking agents, including other nitrogen mustards, which may be an important contribution to its clinical efficacy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1766. doi:1538-7445.AM2012-1766

Expression and Purification of the Human Xeroderma Pigmentosum F (XPF/ERCC1) Complex in Bacterial Cells for Protein Binding Assays and Crystallographic Studies

Mutations in dna repair enzymes of the XP complementation group, XPA‐XPG, leads to a number of genetic disorders such as Xeroderma Pigmentosum, Cockayne's Syndrome, and Trichothiodystrophy. The structure specific dna repair endonuclease responsible for the 5′ incision during dna repair, XPF, is involved in homologous recombination that assists in removing interstrand cross‐link. XP‐F is an autosomal recessive disease characterized by hypersensitivity of the skin to sunlight followed by high incidence of skin cancer and frequent neurologic abnormalities. I expressed and purified human recombinant XPF and ERCC1 proteins in E.Coli Rosetta and BL21 cells, these results will be scaled up for use in interaction and crystallographic studies with proteins of the XP family.