PKP1 and skin cancer: The decrease of DSG1, DSC2, DSC3, DSG3, PG, PKP1-3, and DSP expression associated with poor prognosis in patients with multiple cancers such as head and neck cancer, colon cancer, skin cancer, esophageal cancer, lung cancer, cervical cancer, and gastric cancer [15,16,17,18,19,20,21,22].