Synthesis and Cytotoxicity Assay of Aniline Substituted Thienopyrimidines for Anti-Colorectal Cancer Activity

Colorectal cancer had a low incidence several decades ago. However, it has become a predominant cancer and now accounts for approximately 10% of cancer-related mortality in western countries. The 'rise' of colorectal cancer in developed countries can be attributed to the increasingly ageing population, unfavourable modern dietary habits and an increase in risk factors, such as smoking, low physical exercise and obesity. New treatments for primary and metastatic colorectal cancer have emerged, providing additional options for patients; these treatments include laparoscopic surgery for primary disease, more-aggressive resection of metastatic disease (such as liver and pulmonary metastases), radiotherapy for rectal cancer, and neoadjuvant and palliative chemotherapies. However, these new treatment options have had limited impact on cure rates and long-term survival. For these reasons, and the recognition that colorectal cancer is long preceded by a polypoid precursor, screening programmes have gained momentum. This Primer provides an overview of the current state of the art of knowledge on the epidemiology and mechanisms of colorectal cancer, as well as on diagnosis and treatment.

The MTT tetrazolium salt colorimetric assay previously described by Mosmann (1983, J. Immunol. Methods 65, 55) to measure cytotoxicity and cell proliferation was further explored to extend its application to the measurement of cell activation. The level of MTT cleavage by viable cells of various origins was found to be directly proportional to the number of cells but to increase as a non-linear function of time. This non-linear relationship was related to a time-linear cell death during MTT incubation. The cleavage of MTT by viable cells was found to follow first order kinetics and could be fitted to Michaelis' kinetics. Different cell types exhibited similar apparent Km values (1949 microM) and different apparent maximal velocities (V). The apparent V values determined for a given cell type under different experimental conditions were rigorously similar. This analysis of MTT cleavage by viable cells suggests that the colorimetric MTT test can be useful to quantify the activation level of cells, independently of proliferation.

Colorectal cancer (CRC) is often diagnosed at an advanced stage when tumor cell dissemination has taken place. Chemo- and targeted therapies provide only a limited increase of overall survival for these patients. The major reason for clinical outcome finds its origin in therapy resistance. Escape mechanisms to both chemo- and targeted therapy remain the main culprits. Here, we evaluate major resistant mechanisms and elaborate on potential new therapies. Amongst promising therapies is α-amanitin antibody-drug conjugate targeting hemizygous p53 loss. It becomes clear that a dynamic interaction with the tumor microenvironment exists and that this dictates therapeutic outcome. In addition, CRC displays a limited response to checkpoint inhibitors, as only a minority of patients with microsatellite instable high tumors is susceptible. In this review, we highlight new developments with clinical potentials to augment responses to checkpoint inhibitors.