Tiny Aduro Biotech Inc. hopes to put the STING on cancer with a potential $750 million deal between the Berkeley company and drug giant Novartis AG. The deal centers on experimental synthetic small molecules, developed by Aduro, that could be the latest weapon in the hot field of cancer immunotherapy. The molecules bind to a receptor for a protein known as STING, which researchers believe plays a critical role in helping the immune system recognize and marshal its tumor-fighting forces against cancer. What's…