For example, in squamous cell NSCLC elevated levels of histone deacetylases (HDAC), such as HDAC3 and HDAC6, are detected, that are reported to upregulate PD-L1 expression by STAT3 signalling pathway in melanoma, osteosarcoma, and pancreatic cancer [77,78]. Here, STAT3 is linked to osteosarcoma.