The combination of TRPM8 and TRPA1 expression causes an invasive phenotype in lung cancer

Tumour Biol. 2014 Feb;35(2):1251-61. doi: 10.1007/s13277-013-1167-3. Epub 2013 Sep 15.

Abstract

Our recent studies have shown that hypothermic microenvironment promotes tumor progression and that the molecular sensors for cold are the transient receptor potential (TRP) channels TRPM8 and TRPA1. To evaluate the contribution of TRPM8 and TRPA1 to cancer malignancy, we screened cell subpopulations from Lewis lung cancer (LLC) using limiting dilutions and Western blotting. We identified that LLC-1 cells express 3-fold more TRPM8 than TRPA1, LLC-2 cells express TRPM8 at levels similar to TRPA1, and LLC-3 cells express TRPM8 at one-third the level of TRPA1. LLC-2 cells showed greater adhesion, migration, invasiveness and resistance to hypothermia than LLC-1 and LLC-3 cells, although LLC-2 cells had a longer doubling time. TRPM8 or TRPA1 knockdown using siRNA promoted cell proliferation and decreased adhesion and invasiveness in LLC-2 cells. When assessed for UCP2 staining, LLC-1 cells showed increased staining compared to LLC-2 cells, both of which had more UCP2-positive cells than the LLC-3 subpopulation. In an autophagy assay, hypothermia induced substantially less autophagy in LLC-1 cells than in LLC-2 cells, which displayed decreased autophagy compared to LLC-3 cells. Moreover, mice injected with LLC-2 cells had significantly more spontaneous and experimental lung metastases and a shorter overall survival time than mice injected with LLC-1 or LLC-3 cells. Importantly, LLC-2 cells were also more resistant to activated spleen CTL and the chemotherapeutic drug doxorubicin than LLC-1 and LLC-3 cells in vitro. Collectively, our data suggest that TRPM8 induces UCP2 to trigger metabolic transformation, whereas TRPA1 induces autophagy during adverse conditions, and the combination of both genes contributes directly to an invasive phenotype in lung cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Channels / biosynthesis
  • Calcium Channels / genetics*
  • Carcinoma, Lewis Lung / genetics*
  • Carcinoma, Lewis Lung / pathology
  • Cell Line, Tumor
  • Cell Proliferation
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Ion Channels / metabolism
  • Mice
  • Mitochondrial Proteins / metabolism
  • Neoplasm Invasiveness / genetics*
  • Nerve Tissue Proteins / biosynthesis
  • Nerve Tissue Proteins / genetics*
  • RNA, Small Interfering
  • TRPA1 Cation Channel
  • TRPM Cation Channels / biosynthesis
  • TRPM Cation Channels / genetics*
  • Transient Receptor Potential Channels / biosynthesis
  • Transient Receptor Potential Channels / genetics*
  • Uncoupling Protein 2

Substances

  • Calcium Channels
  • Ion Channels
  • Mitochondrial Proteins
  • Nerve Tissue Proteins
  • RNA, Small Interfering
  • TRPA1 Cation Channel
  • TRPA1 protein, human
  • TRPM Cation Channels
  • TRPM8 protein, human
  • Transient Receptor Potential Channels
  • UCP2 protein, human
  • Ucp2 protein, mouse
  • Uncoupling Protein 2