RB1 and lymphoma: The p16 gene and protein expression was low in six out of eight (6/8) canine lymphoma cell lines, in which four out of six (4/6) cell lines (CLBL-1, CLC, Nody-1, and UL-1) may have hypermethylation of the p16 gene, decreased expression of the p16 protein, and hyperphosphorylated pRb.