MiR-1253 exerts tumor-suppressive effects in medulloblastoma via inhibition of CDK6 and CD276 (B7-H3)

Of the four primary subgroups of medulloblastoma, the most frequent cytogenetic abnormality, i17q, distinguishes Groups 3 and 4 which carry the highest mortality; haploinsufficiency of 17p13.3 is a marker for particularly poor prognosis. At the terminal end of this locus lies miR-1253, a brain-enriched microRNA that regulates bone morphogenic proteins during cerebellar development. We hypothesized miR-1253 confers novel tumor-suppressive properties in medulloblastoma. Using two different cohorts of medulloblastoma samples, we first studied the expression and methylation profiles of miR-1253. We then explored the anti-tumorigenic properties of miR-1253, in parallel with a biochemical analysis of apoptosis and proliferation, and isolated oncogenic targets using high-throughput screening. Deregulation of miR-1253 expression was noted, both in medulloblastoma clinical samples and cell lines, by epigenetic silencing via hypermethylation; specific de-methylation of miR-1253 not only resulted in rapid recovery of expression but also a sharp decline in tumor cell proliferation and target gene expression. Expression restoration also led to a reduction in tumor cell virulence, concomitant with activation of apoptotic pathways, cell cycle arrest and reduction of markers of proliferation. We identified two oncogenic targets of miR-1253, CDK6 and CD276, whose silencing replicated the negative trophic effects of miR-1253. These data reveal novel tumor-suppressive properties for miR-1253, i.e., (i) loss of expression via epigenetic silencing; (ii) negative trophic effects on tumor aggressiveness; and (iii) downregulation of oncogenic targets.

17p13.3 microduplication, a potential novel genetic locus for nonsyndromic bilateral cleft lip and palate

Cleft lip and palate (CLP) is a relatively common congenital malformation. The etiology is complex and postulated to be a combination of genetic and environmental factors. The genetic loci for nonsyndromic CLP remain poorly characterized. Two families have recently been reported with a chromosome 17p13.3 microduplication and CLP. We report a third family with four individuals affected by nonsyndromic bilateral CLP and a 350-kb chromosome 17p13.3 microduplication (17:1,113,102-1,461,838). Our family possesses the smallest overlapping chromosome 17p13.3 microduplication associated with CLP, narrowing down the critical region for this potential new genetic locus for CLP.

Prognostic significance of loss of heterozygosity at loci on chromosome 17p13.3-ter in sporadic breast cancer is evidence for a putative tumour suppressor gene

Several studies indicate that the short arm of chromosome 17 is one of the most frequently altered regions in sporadic breast carcinomas (45-60%). In the present report the 17p13.3-ter locus in tumour DNA of breast cancer patients, along with their matching normal lymphocyte DNA, have been mapped with four markers (D17S5, D17S379, ABR and D17S34), spanning nearly 3 cM of the telomer. Sixty-five of 143 heterozygous tumours had lost at least one of the markers at the minimum region of loss (45%). High levels of loss of these distal markers on 17p13.3 are independent of TP53 mutations and are associated with tumour cell proliferation. A follow-up period of over 7 years demonstrates that loss of these markers correlates both with disease-free (P = 0.004) and overall survival (P = 0.007). In addition we show that for disease-free survival the prognostic power of this genetic alteration is second only to axillary lymph node involvement (3.1 vs 6.3 relative risk), and is a better predictor than the mutational status of TP53 (1.6 relative risk). Our results are further evidence of the presence, within the region, of at least a second tumour suppressor gene distal to TP53, that might be targeted by deletions.