Characterization of TNNC1 as a Novel Tumor Suppressor of Lung Adenocarcinoma

Mol Cells. 2020 Jul 31;43(7):619-631. doi: 10.14348/molcells.2020.0075.

Abstract

In this study, we describe a novel function of TNNC1 (Troponin C1, Slow Skeletal and Cardiac Type), a component of actin-bound troponin, as a tumor suppressor of lung adenocarcinoma (LUAD). First, the expression of TNNC1 was strongly down-regulated in cancer tissues compared to matched normal lung tissues, and down-regulation of TNNC1 was shown to be strongly correlated with increased mortality among LUAD patients. Interestingly, TNNC1 expression was enhanced by suppression of KRAS, and ectopic expression of TNNC1 in turn inhibited KRASG12D-mediated anchorage independent growth of NIH3T3 cells. Consistently, activation of KRAS pathway in LUAD patients was shown to be strongly correlated with down-regulation of TNNC1. In addition, ectopic expression of TNNC1 inhibited colony formation of multiple LUAD cell lines and induced DNA damage, cell cycle arrest and ultimately apoptosis. We further examined potential correlations between expression levels of TNNC1 and various clinical parameters and found that low-level expression is significantly associated with invasiveness of the tumor. Indeed, RNA interference-mediated down-regulation of TNNC1 led to significant enhancement of invasiveness in vitro. Collectively, our data indicate that TNNC1 has a novel function as a tumor suppressor and is targeted for down-regulation by KRAS pathway during the carcinogenesis of LUAD.

Keywords: KRAS; TNNC1; invasion; lung adenocarcinoma; tumor suppressor.

MeSH terms

  • Adenocarcinoma of Lung / genetics
  • Adenocarcinoma of Lung / metabolism*
  • Adenocarcinoma of Lung / mortality
  • Adenocarcinoma of Lung / pathology
  • Animals
  • Apoptosis / genetics
  • Cell Cycle Checkpoints / genetics
  • Cell Line, Tumor
  • DNA Damage / genetics
  • Down-Regulation
  • Gene Expression Regulation, Neoplastic / genetics
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism*
  • Lung Neoplasms / mortality
  • Lung Neoplasms / pathology
  • Mice
  • Middle Aged
  • NIH 3T3 Cells
  • Neoplasm Invasiveness / genetics
  • Neoplasm Staging
  • Proto-Oncogene Proteins p21(ras) / genetics
  • Proto-Oncogene Proteins p21(ras) / metabolism*
  • RNA, Small Interfering
  • Signal Transduction / genetics
  • Troponin I / genetics
  • Troponin I / metabolism*
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*

Substances

  • KRAS protein, human
  • RNA, Small Interfering
  • TNNI1 protein, human
  • Troponin I
  • Tumor Suppressor Proteins
  • Proto-Oncogene Proteins p21(ras)