Cancer-Associated Fibroblast Induces Acinar-to-Ductal Cell Transdifferentiation and Pancreatic Cancer Initiation Via LAMA5/ITGA4 Axis

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is characterized by desmoplastic stroma surrounding most tumors. Activated stromal fibroblasts, namely cancer-associated fibroblasts (CAFs), play a major role in PDAC progression. We analyzed whether CAFs influence acinar cells and impact PDAC initiation, that is, acinar-to-ductal metaplasia (ADM). ADM connection with PDAC pathophysiology is indicated, but not yet established. We hypothesized that CAF secretome might play a significant role in ADM in PDAC initiation.

METHODS

Mouse and human acinar cell organoids, acinar cells cocultured with CAFs and exposed to CAF-conditioned media, acinar cell explants, and CAF cocultures were examined by means of quantitative reverse transcription polymerase chain reaction, RNA sequencing, immunoblotting, and confocal microscopy. Data from liquid chromatography with tandem mass spectrometry analysis of CAF-conditioned medium and RNA sequencing data of acinar cells post-conditioned medium exposure were integrated using bioinformatics tools to identify the molecular mechanism for CAF-induced ADM. Using confocal microscopy, immunoblotting, and quantitative reverse transcription polymerase chain reaction analysis, we validated the depletion of a key signaling axis in the cell line, acinar explant coculture, and mouse cancer-associated fibroblasts (mCAFs).

RESULTS

A close association of acino-ductal markers (Ulex europaeus agglutinin 1, amylase, cytokeratin-19) and mCAFs (α-smooth muscle actin) in LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx1Cre (KPC) and LSL-KrasG12D/+; Pdx1Cre (KC) autochthonous progression tumor tissue was observed. Caerulein treatment-induced mCAFs increased cytokeratin-19 and decreased amylase in wild-type and KC pancreas. Likewise, acinar-mCAF cocultures revealed the induction of ductal transdifferentiation in cell line, acinar-organoid, and explant coculture formats in WT and KC mice pancreas. Proteomic and transcriptomic data integration revealed a novel laminin α5/integrinα4/stat3 axis responsible for CAF-mediated acinar-to-ductal cell transdifferentiation.

CONCLUSIONS

Results collectively suggest the first evidence for CAF-influenced acino-ductal phenotypic switchover, thus highlighting the tumor microenvironment role in pancreatic carcinogenesis inception.

Elevated PAF1-RAD52 axis confers chemoresistance to human cancers

Cisplatin- and gemcitabine-based chemotherapeutics represent a mainstay of cancer therapy for most solid tumors; however, resistance limits their curative potential. Here, we identify RNA polymerase II-associated factor 1 (PAF1) as a common driver of cisplatin and gemcitabine resistance in human cancers (ovarian, lung, and pancreas). Mechanistically, cisplatin- and gemcitabine-resistant cells show enhanced DNA repair, which is inhibited by PAF1 silencing. We demonstrate an increased interaction of PAF1 with RAD52 in resistant cells. Targeting the PAF1 and RAD52 axis combined with cisplatin or gemcitabine strongly diminishes the survival potential of resistant cells. Overall, this study shows clinical evidence that the expression of PAF1 contributes to chemotherapy resistance and worse clinical outcome for lethal cancers.

Metabolic programming of distinct cancer stem cells promotes metastasis of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) metastasizes to distant organs, which is the primary cause of mortality; however, specific features mediating organ-specific metastasis remain unexplored. Emerging evidence demonstrates that cancer stem cells (CSCs) and cellular metabolism play a pivotal role in metastasis. Here we investigated the role of distinct subtypes of pancreatic CSCs and their metabolomic signatures in organ-specific metastatic colonization. We found that PDAC consists of ALDH+/CD133+ and drug-resistant (MDR1+) subtypes of CSCs with specific metabolic and stemness signatures. Human PDAC tissues with gemcitabine treatment, autochthonous mouse tumors from Kras^G12D; Pdx1-Cre (KC) and Kras^G12D; Trp53^R172H; Pdx-1 Cre (KPC) mice, and KPC- Liver/Lung metastatic cells were used to evaluate the CSC, EMT (epithelial-to-mesenchymal transition), and metabolic profiles. A strong association was observed between distinct CSC subtypes and organ-specific colonization. The liver metastasis showed drug-resistant CSC- and EMT-like phenotype with aerobic glycolysis and fatty acid β-oxidation-mediated oxidative (glyco-oxidative) metabolism. On the contrary, lung metastasis displayed ALDH+/CD133+ and MET-like phenotype with oxidative metabolism. These results were obtained by evaluating FACS-based side population (SP), autofluorescence (AF+) and Alde-red assays for CSCs, and Seahorse-based oxygen consumption rate (OCR), extracellular acidification rate (ECAR), and fatty acid β-oxidation (FAO)-mediated OCR assays for metabolic features along with specific gene signatures. Further, we developed in vitro human liver and lung PDAC metastasis models by using a combination of liver or lung decellularized scaffolds, a co-culture, and a sphere culture methods. PDAC cells grown in the liver-mimicking model showed the enrichment of MDR1+ and CPT1A+ populations, whereas the PDAC cells grown in the lung-mimicking environment showed the enrichment of ALDH+/CD133+ populations. In addition, we observed significantly elevated expression of ALDH1 in lung metastasis and MDR1/LDH-A expression in liver metastasis compared to human primary PDAC tumors. Our studies elucidate that distinct CSCs adapt unique metabolic signatures for organotropic metastasis, which will pave the way for the development of targeted therapy for PDAC metastasis.