Optimized from the purine template of seliciclib, CCT068127 exhibits greater potency and selectivity against purified CDK2 and CDK9 and superior antiproliferative activity against human colon cancer and melanoma cell lines.
To identify miR-514a regulated targets we conducted a miR-514a-mRNA 'pull-down' experiment, which revealed hundreds of genes, including: CTNNB1, CDK2, MC1R, and NF1, previously associated with melanoma.
Overall, our results show how CDK2 blockade may offer a promising therapy for genetically defined melanomas, where NUAK2 is amplified and PTEN is deleted.
Such subsets of familial pancreatic cancer involve germline cationic trypsinogen or PRSS1 mutations (hereditary pancreatitis), BRCA2 mutations (usually in association with hereditary breast-ovarian cancer syndrome), CDKN2 mutations (familial atypical mole and multiple melanoma), or DNA repair gene mutations (e.g., ATM and PALB2, apart from those in BRCA2).
It causes growth arrest in melanocytes, associated with the inhibition of Cyclin E/Cdk2 and β-catenin phosphorylation at the transcriptional activity site Ser(552) and is silenced through DNA methylation in 27/35 (77%) melanoma tissues/early cultures.
Through DNA microarray analysis, we found that the antimelanoma effect of IFN-gamma in DM6 was associated with the down-regulation of multiple genes involved in G-protein signaling and phospholipase C activation (including Rap2B and calpain 3) as well as the down-regulation of genes involved in melanocyte/melanoma survival (MITF and SLUG), apoptosis inhibition (Bcl2A1 and galectin-3), and cell cycling (CDK2).
We have therefore studied the prevalence of germline 9p deletions encompassing the CDKN2 locus in melanoma pedigrees, using multiplex ligation-dependent probe amplification.
Collectively, these data indicate that CDK2 activity in melanoma is largely maintained at the transcriptional level by MITF, and unlike other malignancies, it may be a suitable drug target in melanoma.
We also examined the expression of the CDK2 gene in melanoma cell lines, to assess its possible co-regulation with the gene for the melanocyte-lineage antigen pmel17, which maps less than 1 kb away in head to head orientation with CDK2 and may be transcribed off the same bidirectional promoter.
Our recent studies have demonstrated that the two tumor suppressor genes, p53 and p16/CDKN2, do not play a major role in the acquisition of the metastatic phenotype in human melanoma.
The occurrence of p16/CDKN2 germline mutations in 12 Icelandic melanoma kindreds (kindreds with two or more cases of melanoma or melanoma, pancreas and/or glioma cases) was examined.
We have identified two novel CDKN2 mutations (88delG and Ala118Thr) which are likely to be associated with the development of melanoma, because of their co-segregation with the disease and their likely functional effect on the CDKN2 protein.
These data strongly support the idea that deregulation of the CDK4/cyclin D pathway, via CDKN2 or CDK4 mutations, is of biological significance in the development of melanoma.
Although a low frequency of CDKN2 DNA aberrations was observed, the high number of tumours that lackedCDKN2 expression but showed overexpression of CDK4 and/or CCND1, suggest that functional inactivation of pRb through this pathway may be involved in the development or progression of sporadic human melanomas.
Our results support the following conclusions: (i) somatic mutation of the CDKN2 gene is rare in sporadic melanomas with allelic loss at 9p21; (ii) homozygous loss is more frequent than mutation of the CDKN2 gene in sporadic melanomas; (iii) at 9p21-p23 genes other than CDKN2 may be involved in the development of sporadic melanomas.
As reported previously, the mutational spectrum of CDKN2 in melanomas differs from that of internal malignancies and supports the involvement of UV in melanoma tumorigenesis.
The results support an involvement of the CDKN2 product in the development of a subgroup of sporadic melanomas and encourage the search for alterations in additional genes of the 9p21 region.
In seven kindreds (including our six largest), CDKN2 mutations were found to segregate with the putative melanoma chromosome previously assigned by 9p haplotype analysis.
Loss of heterozygosity studies in melanoma and pancreatic carcinoma from gene carriers strongly support the view that CDKN2 is a general tumour suppressor gene predisposing not only to melanoma but also to other malignancies.