Genetic and Epigenetic Analysis of the Putative Tumor Suppressor <i>km23</i> in Primary Ovarian, Breast, and Colorectal Cancers

Campbell, Ian; Phillips, Wayne A.; Choong, David Y.H.

doi:10.1158/1078-0432.ccr-06-0800

Cited by 10 publications

(5 citation statements)

References 10 publications

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“…Hence we believe that contamination is not an issue. Somatic hypermethylation events have been reported for km23 (a TGF-β receptor-interacting protein), ATM, BRCA1 & 2 [48][49][50]. Our observations on the existence of somatic hypermethylation of BRMS1 may have a bearing on the susceptibility to develop breast cancer metastases or overall patient prognosis; however this study is underpowered to address this issue.…”

Section: Discussionmentioning

confidence: 81%

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

Metge

Frost

King

et al. 2008

Clin Exp Metastasis

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Breast Cancer Metastasis Suppressor 1 (BRMS1) suppresses metastasis of human breast cancer, ovarian cancer and melanoma in athymic mice. Studies have also shown that BRMS1 is significantly downregulated in some breast tumors, especially in metastatic disease. However, the mechanisms which regulate BRMS1 expression are currently unknown. Upon examination of the BRMS1 promoter region by methylation specific PCR (MSP) analysis, we discovered a CpG island (−3477 to −2214), which was found to be hypermethylated across breast cancer cell lines. A panel of 20 patient samples analyzed showed that 45% of the primary tumors and 60% of the matched lymph node metastases, displayed hypermethylation of BRMS1 promoter. Furthermore, we found a direct correlation between the methylation status of the BRMS1 promoter in the DNA isolated from tissues, with the loss of BRMS1 expression assessed by immunohistochemistry. There are several studies investigating the mechanism by which BRMS1 suppresses metastasis; however thus far there is no

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Section: Discussionmentioning

confidence: 81%

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

Metge

Frost

King

et al. 2008

Clin Exp Metastasis

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“…However, in approximately 30–40% of colon cancers, the mechanism(s) resulting in impaired TGF-β signaling is not known. Some investigators have shown that epigenetic alterations can affect KM23, TGFBI (Betaig-h3 gene), and RUNX3 , which are all genes involved with regulation of the TGF-β signaling pathway, but none of these studies have demonstrated that the aberrant methylation of these genes directly alters the TGF-β signaling pathway 40–42. We have provided evidence that TGF-β1 activation is impaired when TSP1 is aberrantly methylated resulting in the suppression of TGF-β receptor activation.…”

Section: Discussionmentioning

confidence: 99%

“…Some investigators have shown that epigenetic alterations can affect KM23, TGFBI (Betaig-h3 gene), and RUNX3, which are all genes involved with regulation of the TGF-b signaling pathway, but none of these studies have demonstrated that the aberrant methylation of these genes directly alters the TGF-b signaling pathway. [40][41][42] We have provided evidence that TGF-b1 activation is impaired when TSP1 is aberrantly methylated resulting in the suppression of TGF-b receptor activation. These results provide the first evidence of which we are aware that an epigenetic event can attenuate TGF-b responsiveness in colon cancer.…”

Section: Discussionmentioning

confidence: 99%

The aberrant methylation of TSP1 suppresses TGF‐β1 activation in colorectal cancer

Rojas¹,

Meherem²,

Kim³

et al. 2008

Intl Journal of Cancer

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Colorectal cancer arises from the progressive accumulation of mutations and epigenetic alterations in colon epithelial cells. Such alterations often deregulate signaling pathways that affect the formation of colon cancer, such as the Wnt, RAS-MAPK and TGF-b pathways. The tumor promoting effects of mutations in genes, such as APC, have been demonstrated in cancer cell lines and in mouse models of intestinal cancer; however, the biological effects of most epigenetic events identified in colorectal cancer remain unknown. Consequently, we assessed whether the aberrant methylation of TSP1, the gene for thrombospondin 1, a regulator of TGF-b ligand activation, is an epigenetic mechanism for inhibiting the TGF-b signaling pathway. We found methylated TSP1 occurs in colon cancer cell lines (33%), colon adenomas (14%) and colon adenocarcinomas (21%). In primary colorectal cancers, loss of TSP1 expression correlated with impaired TGF-b signaling as indicated by decreased Smad2 phosphorylation and nuclear localization. Furthermore, methylation-induced silencing of TSP1 expression reduced the concentration of secreted active TGF-b1 and attenuated TGF-b signaling. Reversal of TSP1 methylation resulted in increased TSP1 mediated activation of the latent LAP:TGF-b complex and subsequent TGF-b receptor activation. Our results demonstrate that the aberrant methylation of TSP1 has biological consequences and provide evidence that the aberrant methylation of TSP1 is a novel epigenetic mechanism for suppressing TGF-b signaling in colorectal cancer. ' 2008 Wiley-Liss, Inc.Key words: thrombospondin; transforming growth factor b; methylation; colorectal cancer; epigenetics Colorectal cancer is the third most common cancer in the United States. In 2008, 154,000 new cases of colorectal cancer will be diagnosed and more than 52,000 people are predicted to die from the disease. 1 Colon cancer arises from the accumulation of DNA alterations in colon epithelial cells, which mediate the initiation and progression of this cancer. Mutations in genes such as KRAS, TP53 and members of the transforming growth factor (TGF-b) signaling pathway play a pathogenic role in the polypcarcinoma sequence. [2][3][4] TGF-b is a pluripotent cytokine that has a multitude of effects on epithelial cells including the inhibition of proliferation, the induction of apoptosis and the stimulation of differentiation. Inactivating mutations in central members of the TGF-b signaling pathway, TGFBR2 and SMAD4, have been identified in approximately half of colon cancers. [5][6][7][8] The biological effects of TGF-b in the colon and the identification of inactivating mutations in TGFBR2 and SMAD4 in colon cancers have demonstrated that the TGF-b signaling pathway can act as a colon cancer tumor suppressor pathway.The TGF-b signaling pathway consists of the TGF-b ligand; the heteromeric TGF-b receptor composed of the type I and type II TGF-b receptors (TGFBR1 and TGFBR2); and the post-receptor signaling proteins, including SMAD2, 3, and 4. TGF-b1 is the most commonly expre...

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“…km23-1, also termed km23 (Campbell et al, 2006; Kang et al, 2007; Tang et al, 2002), Robl1 (Nikulina et al, 2004), DNLC2A (Jiang et al, 2001), mLC7-1 (Tang et al, 2002), DYNLRB1, (Pfister et al, 2005) has been shown to interact with Rab6 (Wanschers et al, 2008), the human reduced folate carrier (Ashokkumar et al, 2009), dynein intermediate chain (DIC) (Susalka et al, 2002; Tang et al, 2002), and LIN-5 and GPR-1/2 in C. elegans (Couwenbergs et al, 2007). We have shown that km23-1 undergoes rapid phosphorylation on serine residues after TßR activation, in keeping with the kinase specificity of the TßRs (Tang et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Requirement for protein kinase A in the phosphorylation of the TGFβ receptor-interacting protein km23-1 as a component of TGFβ downstream effects

Jin

Zhong

Mulder

2013

Experimental Cell Research

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km23-1 was previously identified as a TGFß-receptor interacting protein that was phosphorylated on serines after TGFß stimulation. In the current report, we examined the role of km23-1 phosphorylation in the downstream effects of TGFß/ protein kinase A (PKA) signaling. Using phosphorylation site prediction software, we found that km23-1 has two potential PKA consensus phosphorylation sites. In vitro kinase assays further demonstrated that PKA directly phosphorylates km23-1 on serine 73 (S73). Moreover, our results show that the PKA-specific inhibitor H89 diminishes phosphorylation of km23-1 on S73 after TGFß stimulation. Taken together, our results demonstrate that TGFß induction of PKA activity results in phosphorylation of km23-1 on S73. In order to assess the mechanisms underlying PKA phosphorylation of km23-1 on S73 (S73-km23-1) after TGFß stimulation, immunoprecipitation (IP)/blot analyses were performed, which demonstrate that TGFß regulates complex formation between the PKA regulatory subunit RIß and km23-1 in vivo. In addition, an S73A mutant of km23-1 (S73A-km23-1), which could not be phosphorylated by PKA, inhibited TGFß induction of the km23-1-dynein complex and transcriptional activation of the activin-responsive element (ARE). Furthermore, our results show that km23-1 is required for cAMP-responsive element (CRE) transcriptional activation by TGFß, with S73-km23-1 being required for the CRE-dependent TGFß stimulation of fibronectin (FN) transcription. Collectively, our results demonstrate for the first time that TGFß/PKA phosphorylation of km23-1 on S73 is required for ARE- and CRE-mediated downstream events that include FN induction.

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Genetic and Epigenetic Analysis of the Putative Tumor Suppressor km23 in Primary Ovarian, Breast, and Colorectal Cancers

Cited by 10 publications

References 10 publications

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

The aberrant methylation of TSP1 suppresses TGF‐β1 activation in colorectal cancer

Requirement for protein kinase A in the phosphorylation of the TGFβ receptor-interacting protein km23-1 as a component of TGFβ downstream effects

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