====== CDKN2A homozygous deletion ======

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CDKN2A [[homozygous deletion]] characterizes diffuse malignant [[IDH-mutant glioma]]s with worst outcome.

Microvascular proliferation stratifies IDH-mutant gliomas lacking CDKN2A homozygous deletion.
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[[CDKN2A]], also known as cyclin-dependent kinase inhibitor 2A, is a [[gene]] which in humans is located at [[chromosome 9]], band p21.3.

It is ubiquitously expressed in many tissues and cell types.

The gene codes for two proteins, including the INK4 family member p16 (or p16INK4a) and p14arf.

Both act as tumor suppressors by regulating the cell cycle. p16 inhibits cyclin dependent kinases 4 and 6 (CDK4 and CDK6) and thereby activates the retinoblastoma (Rb) family of proteins, which block traversal from G1 to S-phase. p14ARF (known as p19ARF in the mouse) activates the p53 tumor suppressor. Somatic mutations of CDKN2A are common in the majority of human cancers, with estimates that CDKN2A is the second most commonly inactivated gene in cancer after p53. Germline mutations of CDKN2A are associated with familial melanoma, glioblastoma and pancreatic cancer.

The CDKN2A gene also contains one of 27 SNPs associated with increased risk of coronary artery disease.
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[[MGMT]] and [[CDKN2A]] status subdivided a [[cohort]] into three race-specific groups with different prognoses. This findings indicate that [[bevacizumab]] (BEV) approval in [[Japan]] led to [[overall survival]] (OS) improvement exclusively for patients with concurrent [[unmethylated MGMT promoter]] status and [[CDKN2A homozygous deletion]]
((Funakoshi Y, Hata N, Takigawa K, Arita H, Kuga D, Hatae R, Sangatsuda Y, Fujioka Y, Sako A, Umehara T, Yoshitake T, Togao O, Hiwatashi A, Yoshimoto K, Iwaki T, Mizoguchi M. Clinical significance of [[CDKN2A homozygous deletion]] in combination with [[methylated MGMT status]] for [[IDH-wildtype glioblastoma]]. Cancer Med. 2021 Apr 10. doi: 10.1002/cam4.3860. Epub ahead of print. PMID: 33838014.))
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Meningiomas are heterogeneous tumors as depicted by the current 15 distinct variants defined by histology in the 2021 WHO classification, which also incorporated the first molecular criteria for meningioma grading: homozygous loss of [[CDKN2A]]/B and [[TERT promoter mutation]] as criteria for a WHO grade 3 meningioma.