Nuclear PLD1 combined with NPM1 induces gemcitabine resistance through tumorigenic IL7R in pancreatic adenocarcinoma

Objective:Pancreatic ductal adenocarcinoma(PDAC)is a highly malignant gastrointestinal cancer with a 5-year survival rate of only 9%.Of PDAC patients,15%-20%are eligible for radical surgery.Gemcitabine is an important chemotherapeutic agent for patients with PDAC;however,the efficacy of gemcitabine is limited due to resistance.Therefore,reducing gemcitabine resistance is essential for improving survival of patients with PDAC.Identifying the key target that determines gemcitabine resistance in PDAC and reversing gemcitabine resistance using target inhibitors in combination with gemcitabine are crucial steps in the quest to improve survival prognosis in patients with PDAC.Methods:We constructed a human genome-wide CRISPRa/dCas 9 overexpression library in PDAC cell lines to screen key targets of drug resistance based on sgRNA abundance and enrichment.Then,co-IP,ChIP,ChIP-seq,transcriptome sequencing,and qPCR were used to determine the specific mechanism by which phospholipase D1(PLD1)confers resistance to gemcitabine.Results:PLD1 combines with nucleophosmin 1(NPM1)and triggers NPM1 nuclear translocation,where NPM1 acts as a transcription factor to upregulate interleukin 7 receptor(IL7R)expression.Upon interleukin 7(IL-7)binding,IL7R activates the JAK1/STAT5 signaling pathway to increase the expression of the anti-apoptotic protein,BCL-2,and induce gemcitabine resistance.The PLD1 inhibitor,Vu0155069,targets PLD1 to induce apoptosis in gemcitabine-resistant PDAC cells.Conclusions:PLD1 is an enzyme that has a critical role in PDAC-associated gemcitabine resistance through a non-enzymatic interaction with NPM1,further promoting the downstream JAK1/STAT5/Bcl-2 pathway.Inhibiting any of the participants of this pathway can increase gemcitabine sensitivity.

Photodynamic eradication of intratumoral microbiota with bacteria-targeted micelles overcomes gemcitabine resistance of pancreatic cancer

Increasing evidence suggests that intratumoral microbiota plays a pivotal role in tumor progression,immunosurveillance,metastasis,and chemosensitivity.Particularly,in pancreatic ductal adenocarcinoma,tumor-resident Gammaproteobacteria could transform the chemotherapeutic drug gemcitabine(Gem)into its inactive form,thus rendering chemotherapy ineffective.Herein,a strategy for selectively eradicating intratumoral bacteria was described for overcoming Gem resistance in a pancreatic cancer animal model.An antimicrobial peptide was linked with photosensitizer through a poly(ethylene glycol)chain,which can self-assemble into micelles with a diameter of∼20 nm.The micelles could efficiently kill bacteria under light irradiation by inducing membrane depolarization,thereby inhibiting Gem metabolism.In a bacteria-resident pancreatic cancer animal model,the selective photodynamic eradication of intratumoral bacteria was demonstrated to efficiently reverse Gem resistance.This research highlights antibacterial photodynamic therapy as a promising adjuvant strategy for cancer therapy by modulating intratumoral microbiota.

Promising molecular mechanisms responsible for gemcitabine resistance in cancer

Gemcitabine is the first-line treatment for pancreatic ductual adenocarcinoma(PDAC)as well as acts against a wide range of other solid tumors.Patients usually have a good initial response to gemcitabine-based chemotherapy but would eventually develop resistance.To improve survival and prognosis of cancer patients,better understanding of the mechanisms responsible for gemcitabine resistance and discovery of new therapeutic strategies are in great need.Amounting evidence indicate that the developmental pathways,such as Hedgehog(Hh),Wnt and Notch,become reactivated in gemcitabine-resistant cancer cells.Thus,the strategies for targeting these pathways may sensitize cancer cells to gemcitabine treatment.In this review,we will summarize recent development in this area of research and discuss strategies to overcome gemcitabine resistance.Given the cross-talk between these three developmental signaling pathways,designing clinical trials using a cocktail of inhibitory agents targeting all these pathways may be more effective.Ultimately,our hope is that targeting these developmental pathways may be an effective way to improve the gemcitabine treatment outcome in cancer patients.

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。