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MKK3 sustains cell proliferation and survival through p38DELTA MAPK activation in colorectal cancer.

ABSTRACT: Colorectal cancer (CRC) is one of the most common malignant tumors worldwide and understanding its underlying molecular mechanisms is crucial for the development of therapeutic strategies. The mitogen-activated protein kinase-kinase 3 (MKK3) is a specific activator of p38 MAP kinases (p38 MAPKs), which contributes to the regulation of several cellular functions, such as proliferation, differentiation, apoptosis as well as response to drugs. At present, the exact MKK3/p38 MAPK pathway contribution in cancer is heavily debated because of its pleiotropic function. In this work, we retrospectively explored the prognostic and pathobiologic relevance of MKK3 in a cohort of CRC patients and assessed MKK3 molecular functions in a panel of CRC lines and colonocytes primary cultures. We found increased MKK3 levels in late-stage CRC patients which correlated with shorter overall survival. Herein, we report that the MKK3 targeting by inducible RNA interference univocally exerts antitumor effects in CRC lines but not in primary colonocytes. While MKK3 depletion per se affects growth and survival by induction of sustained autophagy and death in some CRC lines, it potentiates response to chemotherapeutic drug 5-fluorouracil (5-FU) in all of the tested CRC lines in vitro. Here, we demonstrate for the first time that in CRC the MKK3 specifically activates p38delta MAPK isoform to sustain prosurvival signaling and that such effect is exacerbated upon 5-FU challenge. Indeed, p38delta MAPK silencing recapitulates MKK3 depletion effects in CRC cells in vitro and in vivo. Overall, our data identified a molecular mechanism through which MKK3 supports proliferation and survival signaling in CRC, further supporting MKK3 as a novel and extremely attractive therapeutic target for the development of promising strategies for the management of CRC patients.

SUBMITTER: Stramucci L

PROVIDER: S-EPMC6834673 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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MKK3 sustains cell proliferation and survival through p38DELTA MAPK activation in colorectal cancer.

Stramucci Lorenzo L Pranteda Angelina A Stravato Arianna A Amoreo Carla Azzurra CA Pennetti Annarita A Diodoro Maria Grazia MG Bartolazzi Armando A Milella Michele M Bossi Gianluca G

Cell death & disease 20191106 11

Colorectal cancer (CRC) is one of the most common malignant tumors worldwide and understanding its underlying molecular mechanisms is crucial for the development of therapeutic strategies. The mitogen-activated protein kinase-kinase 3 (MKK3) is a specific activator of p38 MAP kinases (p38 MAPKs), which contributes to the regulation of several cellular functions, such as proliferation, differentiation, apoptosis as well as response to drugs. At present, the exact MKK3/p38 MAPK pathway contributio ...[more]

PMID: 31695024

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Project description:BackgroundHighly expressed STOML2 has been reported in a variety of cancers, yet few have detailed its function and regulatory mechanism. This research aims to reveal regulatory mechanism of STOML2 and to provide evidence for clinical therapeutics, via exploration of its role in colorectal cancer, and identification of its interacting protein.MethodsExpression level of STOML2 in normal colon and CRC tissue from biobank in Nanfang Hospital was detected by pathologic methods. The malignant proliferation of CRC induced by STOML2 was validated via gain-of-function and loss-of-function experiments, with novel techniques applied, such as organoid culture, orthotopic model and endoscopy monitoring. Yeast two-hybrid assay screened interacting proteins of STOML2, followed by bioinformatics analysis to predict biological function and signaling pathway of candidate proteins. Target protein with most functional similarity to STOML2 was validated with co-immunoprecipitation, and immunofluorescence were conducted to co-localize STOML2 and PHB. Pathway regulated by STOML2 was detected with immunoblotting, and subsequent experimental therapy was conducted with RAF inhibitor Sorafenib.ResultsSTOML2 was significantly overexpressed in colorectal cancer and its elevation was associated with unfavorable prognosis. Knockdown of STOML2 suppressed proliferation of colorectal cancer, thus attenuated subcutaneous and orthotopic tumor growth, while overexpressed STOML2 promoted proliferation in cell lines and organoids. A list of 13 interacting proteins was screened out by yeast two-hybrid assay. DTYMK and PHB were identified to be most similar to STOML2 according to bioinformatics in terms of biological process and signaling pathways; however, co-immunoprecipitation confirmed interaction between STOML2 and PHB, rather than DTYMK, despite its highest rank in previous analysis. Co-localization between STOML2 and PHB was confirmed in cell lines and tissue level. Furthermore, knockdown of STOML2 downregulated phosphorylation of RAF1, MEK1/2, and ERK1/2 on the MAPK signaling pathway, indicating common pathway activated by STOML2 and PHB in colorectal cancer proliferation.ConclusionsThis study demonstrated that in colorectal cancer, STOML2 expression is elevated and interacts with PHB through activating MAPK signaling pathway, to promote proliferation both in vitro and in vivo. In addition, combination of screening assay and bioinformatics marks great significance in methodology to explore regulatory mechanism of protein of interest.

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MKK3 sustains cell proliferation and survival through p38DELTA MAPK activation in colorectal cancer.

Publications

MKK3 sustains cell proliferation and survival through p38DELTA MAPK activation in colorectal cancer.

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