title: Functional parsing of driver mutations in the colorectal cancer genome reveals numerous suppressors of anchorage-independent growth.
abstract: Landmark cancer genome resequencing efforts are leading to the identification of mutated genes in many types of cancer. The extreme diversity of mutations being detected presents significant challenges to subdivide causal from coincidental mutations to elucidate how disrupted regulatory networks drive cancer processes. Given that a common early perturbation in solid tumor initiation is bypass of matrix-dependent proliferation restraints, we sought to functionally interrogate colorectal cancer candidate genes (CAN-genes) to identify driver tumor suppressors. We have employed an isogenic human colonic epithelial cell (HCEC) model to identify suppressors of anchorage-independent growth by conducting a soft agar-based short hairpin RNA (shRNA) screen within the cohort of CAN-genes. Remarkably, depletion of 65 of the 151 CAN-genes tested collaborated with ectopic expression of K-RAS(V12) and/or TP53 knockdown to promote anchorage-independent proliferation of HCECs. In contrast, only 5 of 362 random shRNAs (1.4%) enhanced soft agar growth. We have identified additional members of an extensive gene network specifying matrix-dependent proliferation, by constructing an interaction map of these confirmed progression suppressors with approximately 700 mutated genes that were excluded from CAN-genes, and experimentally verifying soft agar growth enhancement in response to depletion of a subset of these genes. Collectively, this study revealed a profound diversity of nodes within a fundamental tumor suppressor network that are susceptible to perturbation leading to enhanced cell-autonomous anchorage-independent proliferative fitness. Tumor suppressor network fragility as a paradigm within this and other regulatory systems perturbed in cancer could, in large part, account for the heterogeneity of somatic mutations detected in tumors.
authors.affiliation: Departments of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9039, USA.
authors.forename: Ugur
authors.initials: U
authors.lastname: Eskiocak
authors.forename: Sang Bum
authors.initials: SB
authors.lastname: Kim
authors.forename: Peter
authors.initials: P
authors.lastname: Ly
authors.forename: Andres I
authors.initials: AI
authors.lastname: Roig
authors.forename: Sebastian
authors.initials: S
authors.lastname: Biglione
authors.forename: Kakajan
authors.initials: K
authors.lastname: Komurov
authors.forename: Crystal
authors.initials: C
authors.lastname: Cornelius
authors.forename: Woodring E
authors.initials: WE
authors.lastname: Wright
authors.forename: Michael A
authors.initials: MA
authors.lastname: White
authors.forename: Jerry W
authors.initials: JW
authors.lastname: Shay
mesh_terms: D002448:Cell Adhesion / Q000235:genetics; D048708:Cell Growth Processes / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D055785:Gene Knockdown Techniques; D016147:Genes, Tumor Suppressor; D011905:Genes, ras; D015894:Genome, Human; D045325:HCT116 Cells; D006801:Humans; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D009154:Mutation; D019098:Telomerase / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics
chemical_list: C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D048670:MAP Kinase Kinase 4; C509186:TERT protein, human; D019098:Telomerase