Poly (ADP-ribose) Polymerase-1(PARP1)Expression In Breast Cancer Patients And Its Association With Polymorphisms In PARP1Promoter And3’untranslated Region And Chemotherapy Sensitivity

ObjectiveThe purpose of this study is to assess PARP1expression in triple-negative breast cancer (TNBC) and to evaluate the association between polymorphisms in PARP1promoter or3’untranslated region (3’UTR) and PARP1expression. To study the prognostic significance of PARP1expression in different subcellular localization in invasive breast carcinomas and identify PARP1expression in BC as possible biomarkers of chemotherapy treatment response.MethodsPARP1were assessed by immunohistochemistry in302cases of invasive breast carcinomas. No endocrine therapy, chemotherapy or radiotherapy was offered to patients before surgery. Genomic DNA from breast tumor tissues was isolated using QIAamp DNA Mini Kit, PARP1promoter or3’UTR was amplified using Platinum Taq system (Invitrogen, Carlsbad, CA). The results were analyzed by ABI Variant Reporter v1.1software. We assessed PARP1expression in different chemosensitivity BC specimens based on collagen gel droplet embedded culture-drug sensitivity test (CD-DST)(in vitro) results and chemotherapeutic response of NC (in vivo). The surgical specimens from108patients with BC were recruited for CD-DST and PARP1immunohistological examination before chemotherapy. CD-DST was performed in108patients with invasive breast carcinomas. Surgical specimens from90patients with breast cancer who received neoadjuvant chemotherapy were assessed by comparing with the diagnostic pre-treatment core biopsy and the pathological response to chemotherapy was graded by Miller-Payne grading systemResults1.Tumor samples showed different nuclear (nPARPl) and cytoplasmic (cPARPl) PARP1expression patterns, which were categorized as low/high (nuclear) or negative/positive (cytoplasmic), In a number of cancers (99/302,32.8%) both cytoplasmic and nuclear expression (coPARPl) was seen. 2. PARP1was overexpressed in nuclear (nPARP1), cytoplasm (cPARP1) and nuclear-cytoplasmic coexisting (coPARPl) of187TNBCs in comparison to that of115non-TNBCs (P<0.001). nPARP, cPARP1and coPARP1correlated with triple negative status (P<0.001), ER (P<0.05) and PgR negative status (P<0.001), and molecular subtypes (P<0.05).3. High expression of nPARP1and cPARP1in breast cancer was related to worse progression-free survival (P<0.05). Multivariate cox-regression analysis confirmed that high PARP1expression was an unfavorable predictor of PFS (nPARP1,P=0.017; cPARP1, P=0.043) except nuclear-cytoplasmic coexisting (P=0.980).4. we identified seven published polymorphism sites in the promoter region and in3’UTR of PARP1by sequencing. rs7527192and rs2077197genotypes were found to be significantly associated with the cPARP1expression in TNBC patients (rs7527192AA+GA versus GG, P=0.014; rs2077197AA+GA versus GG, P=0.041). These findings were confirmed in an independent validation set of88TNBCs (rs7527192GG versus GA+AA, P=0.030;rs2077197GG versus GA+AA, P=0.030).5. In the univariable Kaplan-Meier survival analyses, the rs7527192and rs2077197genotypes were not demonstrated to be a significant prognostic indicator (PFS, P=0.521and P=0.288respectively).6. Three published SNPs (rs13306133, rs8679, rs3219149) were identified in PARP13’UTR. No significant differences in genotype frequencies were observed between TNBCs and non-TNBCs. No significant association was observed between PARP1levels and3’UTR SNP genotyping.7. The chemosensitivity to each anticancer drug based on the CD-CST were as follows:EPI,46cases (42.6%); DOC,50cases (46.3%); NVB,18cases (16.7%) and CDDP,33cases (30.6%)8. Higher nuclear PARP1(nPARP1) expression was correlated with increased in vitro chemosensitivity against docetaxel (P=0.001) and epirubicin (P=0.022) based on CD-DST results.9. Tumors with high nPARPl expression were more sensitive to anthracycline/taxane based chemotherapy and associated with pathologic response to NC on univariate and multivariate analyses (P=0.019; P=0.036).ConclusionsThe PARP1over-expression including nuclear, cytoplasm and nuclear-cytoplasmic coexisting is a feature of TNBCs and the assessment of its expression may help to predict the efficacy of chemotherapy with PARP1inhibitor. High expression of nPARP1and cPARP1in breast cancer were related to worse PFS. Certain single nucleotide polymorphisms in PARP1promoter may predict cPARPl over-expression. Nuclear expression of PARP1protein analyzed may be useful as predictive markers for response to neoadjuvant chemotherapy in patients with breast cancer.