18F-fluorodeoxyglucose Uptake with Expression of Excision Repair Cross-complementary Group I and Ribonucleotide Reductase Subunit M1 in Non-small Cell Lung Cancer

Fluorodeoxyglucose positron emission tomography/conlputed tomography （FDG PET/CT） is widely applied in non-small cell lung cancer （NSCLC）. The standardized uptake value （SUV）, a semi-quantitative index, plays an essential role in NSCLC tbr diagnosis, staging, and efficacy evaklation. It has been px3posed that the SUV of tumors may correlate with the presence or absence of chemotherapy resistance-associated biomarkers based on studies that have displayed a close correlation between SUV and the expression levels of excision repair cross-complementary Group 1 （ERCC 1 ）1~1 and Tp53-induced glycolysis and apoptosis regulator.121 FDG avidity of NSCLC and ERCC 1 and ribonucleotide reductase subunit M 1 （RRM 1 ） levels have not been as extensively investigated. Based on these findings, we looked tbr correlations among metabolic parameters （SUVm,,. metabolic tumor volume [MTV], and total lesion glycolysis [TLG]） and ERCC1 and RRM1 expression in patients with NSCLC, to investigate whether FDG uptake reflects the presence or absence ofchemoresistance proteins （ERCC1 and RRM 1 ） within tumor cells.

Development of gemcitabine-resistant patient-derived xenograft models of pancreatic ductal adenocarcinoma

Aim:Gemcitabine is a frontline agent for locally-advanced and metastatic pancreatic ductal adenocarcinoma(PDAC),but neither gemcitabine alone nor in combination produces durable remissions of this tumor type.We developed three PDAC patient-derived xenograft(PDX)models with gemcitabine resistance(gemR)acquired in vivo,with which to identify mechanisms of resistance relevant to drug exposure in vivo and to evaluate novel therapies.Methods:Mice bearing independently-derived PDXs received 100 mg/kg gemcitabine once or twice weekly.Tumors initially responded,but regrew on treatment and were designated gemR.We used immunohistochemistry to compare expression of proteins previously associated with gemcitabine resistance[ribonucleotide reductase subunit M1(RRM1),RRM2,human concentrative nucleoside transporter 1(hCNT1),human equilibrative nucleoside transporter 1(hENT1),cytidine deaminase(CDA),and deoxycytidine kinase(dCK)]in gemR and respective gemcitabine-naïve parental tumors.Results:Parental and gemR tumors did not differ in tumor cell morphology,amount of tumor-associated stroma,or expression of stem cell markers.No consistent pattern of expression of the six gemR marker proteins was observed among the models.Increases in RRM1 and CDA were consistent with in vitro-derived gemR models.However,rather than the expected decreases of hCNT1,hENT1,and dCK,gemR tumors expressed no change in or higher levels of these gemR marker proteins than parental tumors.Conclusion:These models are the first PDAC PDX models with gemcitabine resistance acquired in vivo.The data indicate that mechanisms identified in models with resistance acquired in vitro are unlikely to be the predominant mechanisms when resistance is acquired in vivo.Ongoing work focuses on characterizing unidentified mechanisms of gemR and on identifying agents with anti-tumor efficacy in these gemR models。