Proteomic profiling identifies dysregulated pathways in small cell lung cancer and novel therapeutic targets including PARP1

Cancer Discov. 2012 Sep;2(9):798-811. doi: 10.1158/2159-8290.CD-12-0112. Epub 2012 Sep 6.

Abstract

Small cell lung cancer (SCLC) is an aggressive malignancy distinct from non-small cell lung cancer (NSCLC) in its metastatic potential and treatment response. Using an integrative proteomic and transcriptomic analysis, we investigated molecular differences contributing to the distinct clinical behavior of SCLCs and NSCLCs. SCLCs showed lower levels of several receptor tyrosine kinases and decreased activation of phosphoinositide 3-kinase (PI3K) and Ras/mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase (MEK) pathways but significantly increased levels of E2F1-regulated factors including enhancer of zeste homolog 2 (EZH2), thymidylate synthase, apoptosis mediators, and DNA repair proteins. In addition, PARP1, a DNA repair protein and E2F1 co-activator, was highly expressed at the mRNA and protein levels in SCLCs. SCLC growth was inhibited by PARP1 and EZH2 knockdown. Furthermore, SCLC was significantly more sensitive to PARP inhibitors than were NSCLCs, and PARP inhibition downregulated key components of the DNA repair machinery and enhanced the efficacy of chemotherapy.

Significance: SCLC is a highly lethal cancer with a 5-year survival rate of less than 10%. To date, no molecularly targeted agents have prolonged survival in patients with SCLCs. As a step toward identifying new targets, we systematically profiled SCLCs with a focus on therapeutically relevant signaling pathways. Our data reveal fundamental differences in the patterns of pathway activation in SCLCs and NSCLCs and identify several potential therapeutic targets for SCLCs, including PARP1 and EZH2. On the basis of these results, clinical studies evaluating PARP and EZH2 inhibition, together with chemotherapy or other agents, warrant further investigation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Carcinoma, Non-Small-Cell Lung / drug therapy
  • Carcinoma, Non-Small-Cell Lung / genetics
  • Carcinoma, Non-Small-Cell Lung / metabolism
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Cell Line, Tumor
  • ErbB Receptors / metabolism
  • Humans
  • Indoles / pharmacology
  • Lung Neoplasms / drug therapy*
  • Lung Neoplasms / genetics*
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Molecular Targeted Therapy
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phthalazines / pharmacology
  • Piperazines / pharmacology
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerase Inhibitors*
  • Poly(ADP-ribose) Polymerases / biosynthesis
  • Poly(ADP-ribose) Polymerases / genetics
  • Poly(ADP-ribose) Polymerases / metabolism
  • Proteome / metabolism
  • Proteomics / methods*
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Rad51 Recombinase / metabolism
  • Receptor Protein-Tyrosine Kinases / metabolism
  • Signal Transduction / drug effects
  • Small Cell Lung Carcinoma / drug therapy*
  • Small Cell Lung Carcinoma / genetics*
  • Small Cell Lung Carcinoma / metabolism
  • Small Cell Lung Carcinoma / pathology
  • TOR Serine-Threonine Kinases / metabolism

Substances

  • Indoles
  • Phthalazines
  • Piperazines
  • Poly(ADP-ribose) Polymerase Inhibitors
  • Proteome
  • RNA, Messenger
  • rucaparib
  • PARP1 protein, human
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases
  • Phosphatidylinositol 3-Kinases
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • ErbB Receptors
  • Receptor Protein-Tyrosine Kinases
  • RAD51 protein, human
  • Rad51 Recombinase
  • olaparib