CDKN2A and neoplasm: Another study showed that homozygous or heterozygous deletion of Ptprd in the absence of Cdkn2a, a gene that encodes the tumor suppressors p16Ink4 and p14/p19Arf, resulted in increased tumorigenesis in comparison to mice with Cdkn2a deletion alone, and Ptprd-deficiency may influence which types of tumors form [30].