CDKN2A and pachyonychia congenita: The expression of S1R and TMEM97/S2R was evaluated in cells derived both from primary tumor and metastatic site (i.e., liver), characterized by different doubling time and different mutational status of p53, KRAS, P16/CDKN2A, and SMAD 4 (Table 1), the major driver-genes involved in the pathogenesis of PC (Sipos et al., 2003).