How can making use of a CRISPR-cas9n genetic therapy help in eliminating hereditary non-polyposis colorectal cancer with reduced aftereffects and complications compared to current treatment methods?

Started June 2, 2022

Abstract or project description

Hereditary non-polyposis colorectal cancer (HNPCC) is an inherited disorder where individuals have an increased risk of developing colorectal cancer before the age of 50. Current HNPCC treatments involve invasive surgical procedures with debilitating aftereffects. HNPCC can be linked to mutations in genes like MLH1, MSH2, PMS1, PMS2, and EPCAM, some of which are involved in DNA mismatch repair mechanisms. 70% of the patients affected by HNPCC have mutations in 2 genes, MLH1 and MSH2. MLH1 is involved in DNA mismatch repair by binding to PMS2 protein to form a complex around damaged DNA to direct other proteins to fix the damage. Although MSH2 is also involved in DNA mismatch repair, it is different from MLH1 in that it is a tumor suppressor gene that forms heterodimers with MSH6 to form the MutSα complex and MSH3 to form the MutSβ complex. The MutSα complex repairs base mismatches and short insertion/deletion loops, and the MutSβ complex repairs larger insertion/deletion loops. This review will describe current treatments towards HNPCC and a novel CRISPR-Cas9n-based genetic therapy to treat HNPCC without invasive procedures. First, CRISPR, Cas9n, and the gRNA will be added into a hCMV viral vector as a plasmid with replicative abilities silenced. The hCMV vector with these components will be injected into the superior mesenteric artery. Upon entry into the cell, the Cas9n will initiate single strand breaks in MSH2 and MLH1 genes of progenitor and paneth cells to cut out the mutated copy and put in a new copy. Once after this occurs, the tumor cells will undergo apoptosis because MSH2 will initiate DNA repair through MutSβ and MutSα complexes and MLH1 will initiate repair through a joint combination complex with PMS2. Therefore, using CRISPR-Cas9n can treat HNPCC with reduced aftereffects for patients with mutations in MLH1 and MSH2 genes.