Identification of DOK genes as lung tumor suppressors

Abstract

Genome-wide analyses in human lung adenocarcinoma have identified regions of consistent copy number gain or loss, but in many cases the oncogenes and tumor suppressors presumed to reside in these loci remain to be determined. Here we identify the "Downstream of tyrosine kinase" (Dok) family members Dok1, Dok2 and Dok3 as lung tumor suppressors. Single, double, or triple compound loss of these genes in the mouse results in lung cancer with penetrance and latency dependent on the number of lost Dok alleles, and which is associated with an aberrant expansion and signaling profile of alveolar type II cells and bronchioalveolar stem cells. In human lung adenocarcinoma, we identify DOK2 as a target of copy number loss and mRNA downregulation and find that DOK2 suppresses lung cancer cell proliferation in vitro and in vivo. Given the genomic localization of DOK2, we propose it as an 8p21.3 haploinsufficient human lung tumor suppressor. DOK1, DOK2, and DOK3 are adaptor proteins that function in feedback loops to modulate tyrosine kinase signaling. p62 dok (DOK1), the prototypical DOK family member, was cloned as the major phosphorylation substrate of the p210 bcr/abl oncoprotein in Philadelphia * These authors contributed equally to this work AUTHOR CONTRIBUTIONSA.H.B., M.N., A.M. and P.P.P. designed and analyzed the experiments. B.S.T., C.B., W.L.G., and M.L. performed the human genetic studies. A.V. and N.D.S. analyzed the SNP array data. J.S., N.M., J.T.F., W.L.G., and M.L. coordinated human pathological sample acquisition and distribution. J.T.F. reviewed all mouse pathology. Some of the experiments were performed in the laboratory of P.B.R. A.H.B., M.N., and P.P.P. wrote the manuscript.The authors declare no competing financial interests. NIH Public Access Author ManuscriptNat Genet. Author manuscript; available in PMC 2010 October 18. Published in final edited form as:Nat Genet. We speculated that DOK genes might act as tumor suppressors in solid tissues as well as the hematopoietic compartment, where Dok1 and Dok2 can oppose BCR-ABL-driven leukemogenesis 13,14 . Using an in vivo genetic approach in the mouse, we discovered that Dok1, Dok2, and Dok3 act as tumor suppressors in the lung through their ability to regulate the biology of alveolar type II (AT2) cells and bronchioalveolar stem cells (BASCs). In addition, in a multifaceted analysis of human lung adenocarcinoma samples, we find frequent loss and downregulation of DOK2, consistent with a tumor suppressive role for DOK2 in human cancer. RESULTS Dok1, Dok2, and Dok3 single and compound knockout mice develop lung cancerThe biological functions of Dok1, Dok2, and Dok3 have been studied primarily in the hematopoietic system. To determine if these Dok genes might have functions in other tissues, we investigated the expression of Dok1, Dok2, and Dok3 mRNA in a panel of murine tissues. In addition to high expression in the spleen, the mRNAs of all three Dok family members were expressed at high levels in the lung ( Supplementary Fig. 1a and ref. 3). Wester...

Mice lacking Dok-1, Dok-2, and Dok-3 succumb to aggressive histiocytic sarcoma

“…The incidence of macrophage accumulation in the lung was intermediate (3 of 8) in age-matched Dok-3 À/À mice. Although development of lung adenocarcinoma, but not aggressive HS, has recently been reported in mice lacking Dok-1, Dok-2, and/or Dok-3 on a pure 129S1/SvImj genetic background even at the age of 11-15 months, 23 in this study mice mu- tated in the same genes, but on a 129/SvJ and C57BL/6 mixed background, did not exhibit elevated incidence of lung adenocarcinoma. These different findings are likely due to the difference in the genetic backgrounds.…”

Oncogenic Tyrosine Kinases Target Dok-1 for Ubiquitin-Mediated Proteasomal Degradation To Promote Cell Transformation

“…Dok-1, Dok-2, and Dok-3 constitute a closely related subfamily of the Dok adaptor proteins, which emerged as negative regulators of PTK-induced signaling and cellular transformation driven by OTKs (15,21,63,67,80,95). Findings that their loss promotes transformation or disease progression initiated by deregulated PTKs (4,21,54,63,67,95) suggest that their inactivation could constitute an important component of OTK-driven malignant transformation. However, mechanisms by which OTKs could regulate Dok proteins remained unknown.…”

“…Furthermore, more recent studies have shown that mice with combined Dok-1, Dok-2, and Dok-3 knockouts also succumb to aggressive histiocytic sarcoma (54) or develop lung adenocarcinoma with penetrance and latency dependent on the number of lost Dok family members (4). Finally, DOK-2 has been reported to be a target of frequent copy number loss in human lung cancer (4).…”

A cluster of cooperating tumor-suppressor gene candidates in chromosomal deletions

“…Although DLC1 is at an epicenter of deletions, these deletions are frequently much larger and reduce the dosages of tens or hundreds of genes, often encompassing the entire 8p22 cytoband and beyond (2,5,6). Indeed, multiple candidate TSGs have been proposed in the region (5)(6)(7)(8). Here we explore the hypothesis that chromosome 8p deletions arise owing to selection for the attenuation of multiple genes.…”