Distinct Driver Pathway Enrichments and a High Prevalence of TSC2 Mutations in Right Colon Cancer in Chile: A Preliminary Comparative Analysis.

Colorectal cancer (CRC) is the second leading cause of cancer deaths globally. While ethnic differences in driver gene mutations have been documented, the South American population remains understudied at the genomic level, despite facing a rising burden of CRC. We analyzed tumors of 40 Chilean CRC patients (Chp) using next-generation sequencing and compared them to data from mainly Caucasian cohorts (TCGA and MSK-IMPACT). We identified 388 mutations in 96 out of 135 genes, with TP53 (45%), KRAS (30%), PIK3CA (22.5%), ATM (20%), and POLE (20%) being the most frequently mutated. TSC2 mutations were associated with right colon cancer (44.44% in RCRC vs. 6.45% in LCRC, p-value = 0.016), and overall frequency was higher compared to TCGA (p-value = 1.847 × 10-5) and MSK-IMPACT cohorts (p-value = 3.062 × 10-2). Limited sample size restricts definitive conclusions, but our data suggest potential differences in driver mutations for Chilean patients, being that the RTK-RAS oncogenic pathway is less affected and the PI3K pathway is more altered in Chp compared to TCGA (45% vs. 25.56%, respectively). The prevalence of actionable pathways and driver mutations can guide therapeutic choices, but can also impact treatment effectiveness. Thus, these findings warrant further investigation in larger Chilean cohorts to confirm these initial observations. Understanding population-specific driver mutations can guide the development of precision medicine programs for CRC patients.

Crystal structure and molecular dynamics simulations of a promiscuous ancestor reveal residues and an epistatic interaction involved in substrate binding and catalysis in the ATP-dependent vitamin kinase family members.

Enzymes with hydroxymethylpyrimidine/phosphomethylpyrimidine kinase activity (HMPPK) are essential in the vitamin B1 (thiamine pyrophosphate) biosynthesis and recycling pathways. In contrast, enzymes with pyridoxal kinase activity (PLK) produce pyridoxal phosphate (vitamin B6), an essential cofactor for various biochemical reactions. In the ATP-dependent vitamin kinases family, the members of PLK/HMPPK-like subfamily have both enzymatic activities. It has been proposed that the promiscuous PLK activity of ancestral HMPPK enzymes could have been the starting point for this activity. In earlier work, we reconstructed the ancestral sequences of this family and characterized the substrate specificity of the common ancestor between PLK/HMPPK-like and HMPPK enzymes (AncC). From these studies, the Gln45Met mutation was proposed as a critical event for the PLK activity emergence. Here, we crystallize and determine the AncC structure by X-ray crystallography and assess the role of the Gln45Met mutation by site-directed mutagenesis. Kinetic characterization of this mutant shows a significant increase in the PL affinity. Through molecular dynamics simulation and MM/PBSA calculations some residues, important for substrate interactions and catalysis, were identified in the wild type and in the mutated ancestor. Interestingly, a strong epistatic interaction responsible for the evolutionary pathway of the PLK activity in PLK/HMPPK-like enzymes was revealed. Also, other putative mutations relevant to PLK activity in modern PLK/HMPPK-like enzymes were identified.

Rhabdomyolysis in patients with acute lymphoblastic leukemia

The objective of this paper is to report 5 cases of rhabdomyolysis (RML) in patients with acute leukemia (AL). This occurred consecutively after the administration of chemotherapy, during the ensuing period of myelosuppression. Thirty-six patients with AL received, in a three-month period, 51 cycles of combined chemotherapy which included, in all of them, cytosine arabinoside (ARA-C); among them, along with myelosuppression, five experienced fever, infectious complications, gastrointestinal tract symptoms and severe myalgias. Serum creatine kinase (CK), liver function tests and a light microscopy muscle biopsy were performed on all of them. Ten - 17 days after receiving chemotherapy, five patients (4 males and 1 female) with acute lymphoblastic leukemia developed incapacitating myalgias in neck, thighs and arms. CK and/or alanine aminotransferase and spartate aminotransferase were increased 5-24 times above the normal range in four of these patients, and the muscle byopsy showed focal RML in all five. Myalgias were self-limited and lasted 4-10 days. In addition to the chemotherapy, other factors known to be capable of producing RML, such as sepsis, other medications, and dehydration were found. In conclusion, myalgias were due to focal RML produced probably by a combination of factor, particularly the chemotherapy along with dehydration due to gastrointestinal complications, infection, and the use of diverse antibioticas. The endemic nature of the finding in such a short period of time is outstanding