Characterization of RON protein isoforms in pancreatic cancer: implications for biology and therapeutics.
The RON tyrosine kinase receptor is under investigation as a novel target in pancreatic cancer. While RON mutations are uncommon, RON isoforms are produced in cancer cells via a variety of mechanisms. In this study we sought to: 1) characterize RON isoform expression in pancreatic cancer, 2) investigate mechanisms that regulate isoform expression, and 3) determine how various isoforms effect gene expression, oncogenic phenotypes and responses to RON directed therapies. We quantified RON transcripts in human pancreatic cancer and found expression levels 2500 fold that of normal pancreas with RON isoform expression comprising nearly 50% of total transcript. RNA seq studies revealed that the short form (sfRON) and P5P6 isoforms which have ligand independent activity, induce markedly different patterns of gene expression than wild type RON. We found that transcription of RON isoforms is regulated by promoter hypermethylation as the DNA demethylating agent 5-aza-2'-deoxycytidine decreased all RON transcripts in a subset of pancreatic cancer cell lines. The viability of sfRON-expressing HPDE cells was reduced by a RON specific small molecule inhibitor, while a therapeutic monoclonal antibody had no demonstrable effects. In summary, RON isoforms may comprise half of total RON transcript in human pancreatic cancer and their expression is regulated at least in part by promoter hypermethylation. RON isoforms activate distinct patterns of gene expression, have transforming activity and differential responses to RON directed therapies. These findings further our understanding of RON biology in pancreatic cancer and have implications for therapeutic strategies to target RON activity.
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Jeffery
J
Chakedis
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Randall
R
French
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Michele
M
Babicky
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Dawn
D
Jaquish
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Evangeline
E
Mose
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Peter
P
Cheng
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Patrick
P
Holman
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Haleigh
H
Howard
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Jaclyn
J
Miyamoto
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Paula
P
Porras
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Zakk
Z
Walterscheid
Lead Discovery Center GmbH, Dortmund, Germany.
Carsten
C
Schultz-Fademrecht
Merck KGaA, Darmstadt, Germany.
Christina
C
Esdar
Merck KGaA, Darmstadt, Germany.
Oliver
O
Schadt
Lead Discovery Center GmbH, Dortmund, Germany.
Jan
J
Eickhoff
Department of Surgery, Division of Surgical Oncology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
Andrew M
AM
Lowy
D000818:Animals; D021441:Carcinoma, Pancreatic Ductal / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D064593:Heterografts; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics; D014407:Tumor Cells, Cultured
D007527:Isoenzymes; C080835:RON protein; D020794:Receptor Protein-Tyrosine Kinases
RON; alternative splicing; isoform; pancreatic cancer; tyrosine kinase inhibitor