Fig. S3. Absolute quantification of the indicated species in 3 day CM. (A-D) 8-MDP and dipyridamole were applied to PSC2s conditioning the media at 6.67 uM. A83 was applied to PSC2s conditioning the media at 5 uM. Data show 3 biological replicates +/- SEM except for 293T data which shows one biological replicate. ***, P {less than or equal to} 0.001, ns, not significant (one-way ANOVA with Bonferroni post-tests).
Funding
NIH
NCI
Damon Runyon Cancer Research Foundation
MIT Center for Precision Cancer Medicine and the Ludwig Center at MIT
ARTICLE ABSTRACT
Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer deaths in the United States. The deoxynucleoside analogue gemcitabine is among the most effective therapies to treat PDAC, however, nearly all patients treated with gemcitabine either fail to respond or rapidly develop resistance. One hallmark of PDAC is a striking accumulation of stromal tissue surrounding the tumor, and this accumulation of stroma can contribute to therapy resistance. To better understand how stroma limits response to therapy, we investigated cell-extrinsic mechanisms of resistance to gemcitabine. Conditioned media from pancreatic stellate cells (PSC), as well as from other fibroblasts, protected PDAC cells from gemcitabine toxicity. The protective effect of PSC-conditioned media was mediated by secretion of deoxycytidine, but not other deoxynucleosides, through equilibrative nucleoside transporters. Deoxycytidine inhibited the processing of gemcitabine in PDAC cells, thus reducing the effect of gemcitabine and other nucleoside analogues on cancer cells. These results suggest that reducing deoxycytidine production in PSCs may increase the efficacy of nucleoside analog therapies.
This study provides important new insight into mechanisms that contribute to gemcitabine resistance in PDAC and suggests new avenues for improving gemcitabine efficacy.
