Role of the cyclin-dependent kinase inhibitor CDKN2A in familial melanoma

The cell senescence regulator p16 is a promising cancer prognostic and immune check-point inhibitor (ICI) therapy biomarker

Cyclin-dependent kinase inhibitor 2A (CDKN2A) encodes the cell senescence regulator protein p16. The expression of p16 raises in cell senescence and has a nuclear regulation in cell aging. Meanwhile, it's also reported to inhibit the aggression of several cancers. But its clinical application and role in cancer immunotherapy needs further investigation. We collected the transcriptional data of pan-cancer and normal human tissues from The Cancer Genome Atlas and the Genotype-Tissue Expression databases. CBioPortal webtool was employed to mine the genomic alteration status of CDKN2A across cancers. Kaplan-Meier method and univariate Cox regression were performed for prognostic assessments across cancers, respectively. Gene Set Enrichment Analysis is the main method used to search the associated cancer hallmarks associated with CDKN2A. TIMER2.0 was used to analyze the immune cell infiltration relevance with CDKN2A in pan-cancer. The associations between CDKN2A and immunotherapy biomarkers or regulators were performed by spearman correlation analysis. We found CDKN2A is overexpressed in most cancers and exhibits prognosis predictive ability in various cancers. In addition, it is significantly correlated with immune-activated hallmarks, cancer immune cell infiltrations and immunoregulators. The most interesting finding is that CDKN2A can significantly predict anti-PDL1 therapy response. Finally, specific inhibitors which correlated with CDKN2A expression in different cancer types were also screened by using Connectivity Map (CMap) tool. The results revealed that CDKN2A acts as a robust cancer prognostic and immunotherapy biomarker. Its function in the regulation of cancer cell senescence might shape the tumor microenvironment and contribute to its predictive ability of immunotherapy.

Phytochemical Constituents and Derivatives of Cannabis sativa; Bridging the Gap in Melanoma Treatment

Melanoma is deadly, physically impairing, and has ongoing treatment deficiencies. Current treatment regimens include surgery, targeted kinase inhibitors, immunotherapy, and combined approaches. Each of these treatments face pitfalls, with diminutive five-year survival in patients with advanced metastatic invasion of lymph and secondary organ tissues. Polyphenolic compounds, including cannabinoids, terpenoids, and flavonoids; both natural and synthetic, have emerging evidence of nutraceutical, cosmetic and pharmacological potential, including specific anti-cancer, anti-inflammatory, and palliative utility. Cannabis sativa is a wellspring of medicinal compounds whose direct and adjunctive application may offer considerable relief for melanoma suffers worldwide. This review aims to address the diverse applications of C. sativa's biocompounds in the scope of melanoma and suggest it as a strong candidate for ongoing pharmacological evaluation.

The molecular basis of melanomagenesis and the metastatic phenotype

The last two decades have seen spectacular advances in our understanding of the biology of melanoma and, in particular, have elucidated the mechanisms operative in disease initiation and progression. With respect to the former, the genetics of melanoma and in particular the impact of genetic defects on dysregulation of the cell cycle are key issues in malignant transformation and are a major focus of this review. With respect to the latter, consideration also is given to the acquisition of growth factor autonomy and the capacity for invasion and metastasis from the standpoint of cell adhesion, motility, and matrix digestion. These events have specific morphologic correlates that will be briefly addressed. Where relevant, we will address certain of the modern pharmacogenetic strategies that flow from these novel observations concerning melanoma biology.

Clinical and Molecular Characterization of Patients at Risk for Hereditary Melanoma in Southern Brazil

Melanoma is the most dangerous of all common skin cancers, due to its propensity to metastasize. Therefore, identification of at-risk populations may allow early detection of disease at a curable stage. In Europe and North America, between 8-14% of melanoma patients have a family history of the disease, and a subset of these individuals possess germline mutations in the CDKN2A gene, which encodes the p16(INK4A) and p14(ARF) tumor suppressors. We identified 30 patients (29 families) from Southern Brazil, who had a family history of melanoma and/or pancreatic cancer; or a personal history of multiple primary melanoma. We screened this cohort for mutations in the CDKN2A and CDK4 genes, and detected two functional mutations: a G-34T transversion in 5'untranslated region; and a M53I alteration encoded in exon 2. Both mutants have been previously associated with melanoma and demonstrate founder effects. We conclude that germline mutations of CDKN2A occur in the Brazilian population, and that these mutations likely originated in Europe.

Germline splicing mutations of CDKN2A predispose to melanoma

Coding mutations of the CDKN2A gene on chromosome 9p21 cosegregate with 25-60% of familial melanoma cases, but there remains a number of 9p21-linked kindreds that lack germline coding mutations of CDKN2A. We sequenced CDKN2A exons 1alpha, 2, 3, and the adjacent intronic regions in 167 melanoma-prone families (at least two affected first-degree relatives), and detected four splice site variations, three of which cosegregate with the disease. RT-PCR experiments verified that these three variants, including an AGgt to ATgt mutation that demonstrates a founder effect, do affect splicing. While an exon 1alpha splice donor site mutation incompletely abolishes splicing, the correctly spliced mRNA yields a protein (Q50P) that cannot effectively interact with CDK4. We also performed RT-PCR on mRNA from 16 melanoma-prone kindreds to search for cryptic splice sites deep within introns, but identified no splice variants. Meanwhile, we screened 139 affected families using allele-specific PCR for the recently discovered IVS2-105A>G mutation, but found only one family that possesses this alteration. We conclude that splice site mutations do predispose to disease in a subset of melanoma-prone kindreds. Characterization of additional splice site variants and other noncoding alterations of CDKN2A should allow us to detect a wider range of mutations in at-risk patients.

Concurrent acute lymphoblastic leukemia and juvenile pilocytic astrocytoma in a pediatric patient

The concurrence of acute lymphoblastic leukemia (ALL) and an asymptomatic juvenile pilocytic astrocytoma is described. A 6-year-old boy without clinical evidence of neurofibromatosis had a juvenile pilocytic astrocytoma diagnosed on radiologic examination and before treatment of acute pre-B cell lymphoblastic leukemia. The patient has had a partial resection of the astrocytoma and is 9 months into treatment of his ALL, which is in complete remission. p53 gene mutation was not identified in this patient. The concurrent diagnosis before treatment of ALL and juvenile pilocytic astrocytoma, the latter normally an indolent tumor, suggests that some cases of astrocytoma previously ascribed to radiotherapy or other treatment may in fact be caused by other factors.

Malignant melanoma arising from nevi, p53, p16, and Bcl-2: expression in benign versus malignant components

BACKGROUND

The etiology of malignant melanoma has been the subject of much study. Tumour suppressor genes p53 and p16 and the antiapoptotic, Bcl-2, are implicated in the development and progression of malignant melanoma.

OBJECTIVE

To compare the expression of p53, p16, and the Bcl-2 genes in both benign and malignant components of malignant melanoma arising from pre-existing nevocellular nevi.

METHODS

Twenty cases of malignant melanoma arising from pre-existing nevi were selected and studied by immunohistochemistry for the expression of p53 (D07) CDK4I/MTS-1/INK <4, which detects both wild and mutant type, p16 CDK4I/MTS-1/INK <4, and Bcl-2 using an avidin-biotin technique on formalin-fixed, paraffin-embedded sections.

RESULTS

Fifteen cases demonstrated p53 immunoreactivity in the malignant components ranging from 5 to 20% with no expression being seen in the benign components. The p16 gene showed strong nuclear reactivity in the benign components of 14 cases and weak reaction in 6 cases; the malignant components expressed weak nuclear staining in 18 cases and cytoplasmic staining in all cases. The Bcl-2 gene was expressed strongly to moderately in benign components and weakly in malignant components of nine cases, and was negative in 11 cases.

CONCLUSION

Immunostaining for p53 is expressed only in the malignant component, whereas p16 and Bcl-2 showed decreased staining and a different pattern in malignant compared with benign components. These findings suggest that expression and alterations in the subcellular localization of the cell cycle regulators may contribute to the mechanism of tumourigenesis.

Mutation of the CDKN2A 5' UTR creates an aberrant initiation codon and predisposes to melanoma

Approximately 8-12% of melanoma is inherited in an autosomal dominant fashion with variable penetrance. A chromosome 9p21 locus has been linked to this disease in 50-80% of affected families. CDKN2A (also known as P16, INK4, p16INK4A and MTS1) is allelic to this locus and encodes a cdk4/cdk6 kinase inhibitor that constrains cells from progressing through the G1 restriction point. Although germline CDKN2A coding mutations cosegregate with melanoma in 25-60% of families predisposed to the disease, there remains a number of mutation-negative families that demonstrate linkage of inherited melanoma to 9p21 markers. We show here that a subset of these kindreds possess a G-->T transversion at base -34 of CDKN2A, designated G-34T. This mutation gives rise to a novel AUG translation initiation codon that decreases translation from the wild-type AUG. The G-34T mutation is not seen in controls, segregates with melanoma in families and, on the basis of haplotyping studies, probably arose from a common founder in the United Kingdom. Characterization of this and other CDKN2A non-coding mutations should have an impact on current efforts to identify susceptible melanoma-prone families and individuals.