Aberrant promoter methylation of human DAB2 interactive protein (hDAB2IP) gene in lung cancers

Abstract

The human DOC-2/DAB2 interactive protein gene (hDAB2IP) is a novel member of the Ras GTPase-activating gene family that is known to act as a tumor suppressor gene and is inactivated by methylation in prostate and breast cancers. We established previously a methylation-specific PCR (MSP) for the promoter region (m2a and m2b regions) of hDAB2IP and examined hDAB2IP methylation status in breast cancers. We analyzed the methylation and expression status of hDAB2IP in lung cancers. The methylation status of hDAB2IP was examined in lung cancer cell lines using bisulfite sequencing and MSP. Expression was examined using conventional and real-time RT-PCR, and methylation was found to be inversely correlated with expression, confirming that the MSP can also be used to examine hDAB2IP methylation status in lung cancers. Aberrant methylation was detected at the m2a region in 19 of 47 lung cancer cell lines (40%) and 26 of 70 primary tumors (37%) and at the m2b in 16 lines (34%) and 25 of 70 tumors (36%). Gene expression was restored in methylated cell lines supplemented with 5-aza-2-deoxycytidine, confirming that methylation was responsible for downregulation. We also examined the relationship between hDAB2IP methylation and clinico-pathological features of the lung cancers and found that hDAB2IP methylation was associated with advanced disease stage. Our results demonstrate that hDAB2IP methylation is frequently present in lung cancers and plays a key role in hDAB2IP silencing. hDAB2IP methylation could be used as a biomarker for disease stage, reflecting the degree of clinico-pathological malignancy of lung cancer.

Genetic and epigenetic changes in lung carcinoma and their clinical implications

“…The RASSF1A, APC, ESR1, ABCB1, MT1G, and HOXC9 genes were more frequently methylated in stage I lung adenocarcinomas/squamous cell carcinomas than the non-cancerous lesions, 104 whereas the prevalence of hDAB2IP, H-cadherin, DAL-1, and FBN2 methylation was associated significantly with advanced stage of lung cancer, [105][106][107] indicating that these genes might be involved in different phases of lung cancer progression.…”

Block one, unleash a hundred. Mechanisms of DAB2IP inactivation in cancer

“…[60][61][62][63] These studies focused on a CpG island partially overlapping exon 3, which contains a functional promoter and TSS. Transcripts originating at this TSS are spliced to exon 4 and are predicted to encode the shortest DAB2IP protein isoform (Figure 1).…”

“…Published studies provide compelling evidence that methylation of this region correlates with reduced DAB2IP expression in tumor tissues and cell lines, despite the presence of at least two additional TSSs located, respectively, 130 and 48 kbp upstream, and other functional TSSs further downstream. [60][61][62][63][64][65] It is possible that methylation of this region is sufficient to turn the gene off; alternatively, other sites may be coordinately methylated for efficient DAB2IP silencing. Three additional CpG islands are mapped in the hDAB2IP gene, in some cases corresponding to functional TSSs; little is currently known about the methylation status of these regions in normal or pathological conditions, or its potential impact on DAB2IP transcription.…”

Differential Regulation of RasGAPs in Cancer

“…36 DAB2IP, which is a RasGAP associated with the disabled gene family member DAB2, is also silenced in prostate, breast, lung, and gastrointestinal tumors through aberrant promoter CpG methylation. [128][129][130][131][132] Furthermore, 2 genome-wide studies identified DAB2IP as a putative tumor suppressor in aggressive prostate adenocarcinoma. 133 Unfortunately, little is known about the regulation of DAB2IP in vivo and correlation to Ras activity in the cancer samples analyzed, but together with the observations described below, epigenetic silencing of the various GAPs implicates a general theme that requires further investigation.…”