Protein Kinases as Tumor Biomarkers and Therapeutic Targets

Over the last three decades, neoplasms have become the largest cause of human mortality due to both high tumor incidence and mortality. Chemotherapy is one of the main therapies employed to treat neoplasms. Although classical genotoxic drugs, such as cyclophosphamide, 5-FU, cisplatin and doxorubicin have been applied in clinical settings and have achieved very good treatment efficacy, many cancer patients died of tumor metastasis, drug toxicity or drug resistance due to tumor heterogeneity. Targeted molecular treatments based on the genes, receptors, and kinases expressed by a tumor make individualized treatment possible. Protein kinases catalyze the phosphorylation of proteins and are involved in multiple cellular processes. In many cancers, mutation or abnormal expression of protein kinases is correlated with tumorigenesis, metastasis and resistance to chemotherapy. Tumor-related protein kinases have become important molecular targets and biomarkers. The use of protein kinases as tumor biomarkers primarily focuses on tyrosine and serine/threonine kinases. Many tumor drugs targeting protein kinases, such as monoclonal antibody and tyrosine kinase inhibitors (TKIs), are widely utilized in clinic. Additional drugs aimed at combating drug resistance and metastasis should be developed targeting protein kinases. In this review, we summarize several important protein kinases involved in cancer and analyze why these kinases can be used as biomarkers or targets for cancer diagnosis and/or treatment. Furthermore, numerous drugs targeting protein kinases as well as their development and activity are discussed.