Complex sentence: The investigational therapeutic cancer vaccine is thought to induce a cellular immune response to cancer cells that express MUC1, a glycoprotein antigen that is widely (over-) expressed on common cancers such as lung cancer, breast cancer, prostate cancer and colorectal cancer.
Split into simpler sentences: The investigational therapeutic cancer vaccine is designed to induce an immune response to cancer cells that express MUC1, a glycoprotein antigen widely expressed on common cancers. MUC1 is over-expressed on many cancers such as lung cancer, breast cancer, prostate cancer and colorectal cancer.