Oncogenic KRAS/ERK/JUNB signaling suppresses differentiation regulator GATA6 in pancreatic cancer
Zheng Zhong, Xinang Cao, Pei-Ju Liao, Raman Sethi, Jeffrey A. Klomp, Clint A. Stalnecker, Jinmiao Chen, Yue Wan, Channing J. Der, David M. Virshup
Zheng Zhong, Xinang Cao, Pei-Ju Liao, Raman Sethi, Jeffrey A. Klomp, Clint A. Stalnecker, Jinmiao Chen, Yue Wan, Channing J. Der, David M. Virshup
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Research Article Cell biology Oncology

Oncogenic KRAS/ERK/JUNB signaling suppresses differentiation regulator GATA6 in pancreatic cancer

Abstract

GATA6 is a master regulator of differentiation in the pancreas, and its expression levels determine the 2 main molecular subtypes of pancreatic cancer. High GATA6 levels contribute to the classical pancreatic cancer subtype, which is associated with a higher degree of tumor differentiation and better disease prognosis. However, why GATA6 expression varies across pancreatic cancers and what regulates GATA6 expression remain elusive. Here, we report that oncogenic KRAS-activated ERK signaling suppresses GATA6 transcription in pancreatic cancers. GATA6 mRNA levels inversely correlated with KRAS/ERK activity in pancreatic tumors. A genome-wide CRISPR screen in a GATA6-EGFP reporter knockin cell line identified JUNB as the ERK-regulated transcriptional repressor for GATA6. Active ERK stabilized JUNB protein, while KRAS/ERK inhibition led to ubiquitin-independent proteasomal degradation of JUNB and increased transcription of GATA6. Upregulation of GATA6 enhanced chemosensitivity of pancreatic cancer cells, and KRAS/ERK inhibitors synergized with chemotherapy in a GATA6-dependent manner. Our study identifies how oncogenic KRAS/ERK signaling suppresses GATA6 to cause dedifferentiation in pancreatic cancer. Combining KRAS/ERK inhibitors with standard-of-care chemotherapies could be a promising therapeutic strategy for treating pancreatic cancers.

Authors

Zheng Zhong, Xinang Cao, Pei-Ju Liao, Raman Sethi, Jeffrey A. Klomp, Clint A. Stalnecker, Jinmiao Chen, Yue Wan, Channing J. Der, David M. Virshup

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Figure 9

Upregulating GATA6 enhances chemosensitivity of pancreatic cancer cells.

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Upregulating GATA6 enhances chemosensitivity of pancreatic cancer cells....
(A–C) GATA6 knockout led to EMT and increased stemness in HPAF-II cells. (A) Western blotting confirmed the knockout of GATA6. Numbers 1–3 are 3 single-cell–derived clonal GATA6KO lines. (B) Representative images showing EMT morphology of GATA6KO cells. Scale bar: 100 μm. (C) GATA6KO lines showed increased colony formation capacity when single cells were seeded in 96-well plates. n = 3 biological replicates/condition. The P value of Dunnett’s multiple-comparison test is shown. (D and E) Overexpressing GATA6 slowed the proliferation of Panc08.13 cells. (D) Panc08.13 cells were transduced with lentivirus expressing GATA6S or mCherry as a control. n = 2 biological replicates × 2 technical replicates/condition. (E) Cells were seeded in 96-well plates, and cell proliferation was monitored with the CellTiter-Glo assay. n = 3 biological replicates/condition. P values of 2-tailed, unpaired t test are shown. (F and G) GATA6 affected sensitivity to standard-of-care chemotherapy combinations in HPAF-II (F) and Panc08.13 (G) cells. The concentration (Conc) shown on the x axes of these plots refers to the concentration of 5-FU or gemcitabine in the drug combinations. n = 2–3 biological replicates/condition. (H and I) GATA6 knockout conferred resistance to oxaliplatin in HPAF-II cells. (H) Responses to individual chemotherapy agents were examined for GATA6 WT and knockout HPAF-II cells. Changes in IC50 values relative to WT HPAF-II cells are shown. (I) The dose–response curve to oxaliplatin is shown. n = 2–3 biological replicates/condition. (J and K) Overexpressing GATA6 sensitized Panc08.13 cells to irinotecan and oxaliplatin. (J) Responses to individual chemotherapy agents were examined for parental Panc08.13 as well as GATA6S- or mCherry-overexpressing cells. Changes in IC50 values relative to WT Panc08.13 cells are shown. (I) The dose–response curve to oxaliplatin is shown. n = 2–3 biological replicates/condition. Data are shown as the mean ± SD.