PDCD1 and cancer: In the PDCD1 gene, several polymorphisms have been identified, such as PDCD-1.1 (rs36084323), PDCD-1.3 (rs11568821), PDCD-1.5 (rs2227981), PDCD-1.9 (rs2227982), and so on.[8–10] The association between polymorphisms in PDCD1 gene and cancer risk has been studied in many studies.