TIAM1-RAC1 promote small-cell lung cancer cell survival through antagonizing Nur77-induced BCL2 conformational change

Cell Rep. 2021 Nov 9;37(6):109979. doi: 10.1016/j.celrep.2021.109979.

Abstract

Small-cell lung cancer (SCLC), an aggressive neuroendocrine malignancy, has limited treatment options beyond platinum-based chemotherapy, whereafter acquired resistance is rapid and common. By analyzing expression data from SCLC tumors, patient-derived models, and established cell lines, we show that the expression of TIAM1, an activator of the small GTPase RAC1, is associated with a neuroendocrine gene program. TIAM1 depletion or RAC1 inhibition reduces viability and tumorigenicity of SCLC cells by increasing apoptosis associated with conversion of BCL2 from its pro-survival to pro-apoptotic function via BH3 domain exposure. This conversion is dependent upon cytoplasmic translocation of Nur77, an orphan nuclear receptor. TIAM1 interacts with and sequesters Nur77 in SCLC cell nuclei and TIAM1 depletion or RAC1 inhibition promotes Nur77 translocation to the cytoplasm. Mutant TIAM1 with reduced Nur77 binding fails to suppress apoptosis triggered by TIAM1 depletion. In conclusion, TIAM1-RAC1 signaling promotes SCLC cell survival via Nur77 nuclear sequestration.

Keywords: BCL2; Nur77; RAC; SCLC; TIAM1; apoptosis; neuroendocrine; small cell lung cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Biomarkers, Tumor / genetics
  • Biomarkers, Tumor / metabolism*
  • Cell Proliferation
  • Female
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Mice
  • Mice, Inbred NOD
  • Mice, SCID
  • Nuclear Receptor Subfamily 4, Group A, Member 1 / genetics
  • Nuclear Receptor Subfamily 4, Group A, Member 1 / metabolism*
  • Protein Conformation
  • Proto-Oncogene Proteins c-bcl-2 / chemistry*
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Small Cell Lung Carcinoma / genetics
  • Small Cell Lung Carcinoma / metabolism
  • Small Cell Lung Carcinoma / pathology*
  • T-Lymphoma Invasion and Metastasis-inducing Protein 1 / genetics
  • T-Lymphoma Invasion and Metastasis-inducing Protein 1 / metabolism*
  • Tumor Cells, Cultured
  • Xenograft Model Antitumor Assays
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / metabolism*

Substances

  • BCL2 protein, human
  • Biomarkers, Tumor
  • NR4A1 protein, human
  • Nuclear Receptor Subfamily 4, Group A, Member 1
  • Proto-Oncogene Proteins c-bcl-2
  • RAC1 protein, human
  • T-Lymphoma Invasion and Metastasis-inducing Protein 1
  • TIAM1 protein, human
  • rac1 GTP-Binding Protein