Summary The poor clinical outcome in pancreatic ductal adenocarcinoma (PDA) is attributed to intrinsic chemoresistance and a growth-permissive tumor microenvironment. Conversion of quiescent to activated pancreatic stellate cells (PSCs) drives the severe stromal reaction that characterizes PDA. Here we reveal that the vitamin D receptor (VDR) is expressed in stroma from human pancreatic tumors and that treatment with the VDR ligand calcipotriol markedly reduced markers of inflammation and fibrosis in pancreatitis and human tumor stroma. We show that VDR acts as a master transcriptional regulator of PSCs to reprise the quiescent state resulting in induced stromal remodeling, increased intratumoral gemcitabine, reduced tumor volume and a 57% increase in survival compared to chemotherapy alone. This work describes a molecular strategy through which transcriptional reprogramming of tumor stroma enables chemotherapeutic response and suggests Vitamin D priming as an adjunct in PDA therapy.

Pancreatic cancer is the fourth leading cause of cancer-related death among men and women in the United States. A major challenge in treatment remains patients’ advanced disease at diagnosis. The NCCN Guidelines for Pancreatic Adenocarcinoma provides recommendations for the diagnosis, evaluation, treatment, and follow-up for patients with pancreatic cancer. Although survival rates remain relatively unchanged, newer modalities of treatment, including targeted therapies, provide hope for improving patient outcomes. Sections of the manuscript have been updated to be concordant with the most recent update to the guidelines. This manuscript focuses on the available systemic therapy approaches, specifically the treatment options for locally advanced and metastatic disease.

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis largely due to inefficient diagnosis and tenacious drug resistance. Activation of pancreatic stellate cells (PSCs) and consequent development of dense stroma are prominent features accounting for this aggressive biology 1 , 2 . The reciprocal interplay between PSCs and pancreatic cancer cells (PCCs) not only enhances tumour progression and metastasis but also sustains their own activation, facilitating a vicious cycle to exacerbate tumourigenesis and drug resistance 3 – 7 . Moreover, PSC activation occurs very early during PDAC tumourigenesis 8 – 10 , and activated PSCs comprise a significant fraction of the tumour mass, providing a rich source of readily detectable factors. Therefore, we hypothesized that the communication between PSCs and PCCs could be an Achilles’ heel exploitable to develop effective strategies for PDAC therapy and diagnosis. Here, starting with systematic proteomic investigation of secreted disease mediators and underlying molecular mechanisms, we reveal that leukemia inhibitory factor (LIF) is a key paracrine factor from activated PSCs acting on cancer cells. Both pharmacologic LIF blockade and genetic Lifr deletion significantly slow tumour progression and augment chemotherapy efficacy to prolong survival of PDAC mouse models, mainly by modulating cancer cell differentiation and EMT status. Moreover, we show that, consistently in both mouse models and human PDAC, aberrant production of LIF in the pancreas is unique to pathological conditions and correlates with PDAC pathogenesis, and circulating LIF level changes correlate well with tumour response to therapy. Collectively, these findings uncover a previously unappreciated function of LIF in PDAC tumourigenesis, and suggest its translational potential as an attractive therapeutic target and circulating marker. These studies underscore how a better understanding of cell-cell communications within the tumour microenvironment promotes novel strategies for cancer therapy.

Urgent intervention is required to improve the 5 year survival rate of pancreatic ductal adenocarcinoma (PDAC). While the four-drug regimen, FOLFIRINOX (comprising irinotecan, 5-fluorouracil, oxaliplatin, and leucovorin), has a better survival outcome than the more frequently used gemcitabine, the former treatment platform is highly toxic and restricted for use in patients with good performance status. Since irinotecan contributes significantly to FOLFIRINOX toxicity (bone marrow and gastrointestinal tract), our aim was to reduce the toxicity of this drug by a custom-designed mesoporous silica nanoparticle (MSNP) platform, which uses a proton gradient for high-dose irinotecan loading across a coated lipid bilayer (LB). The improved stability of the LB-coated MSNP (LB-MSNP) carrier allowed less drug leakage systemically with increased drug concentrations at the tumor sites of an orthotopic Kras-derived PDAC model compared to liposomes. The LB-MSNP nanocarrier was also more efficient for treating tumor metastases. Equally important, the reduced leakage and slower rate of drug release by the LB-MSNP carrier dramatically reduced the rate of bone marrow, gastrointestinal and liver toxicity compared to the liposomal carrier. We propose that the combination of high efficacy and reduced toxicity by the LB-MSNP carrier could facilitate the use of irinotecan as a first-line therapeutic to improve PDAC survival.

Study approvalAll animal experiments were performed using protocols approved by the UCLA Animal Research Committee. UCLA Institutional Review Board approval was given for collection of samples from human subjects and informed consent was given by all participating human subjects.