A genetic variant of 5-hydroxytryptamine receptor 3C (HTR3C): A novel link to chemotherapy-induced side effects.

Abstract

9630 Background: Symptom clusters are defined as three or more concurrent symptoms that are related to each other. Clusters may stem from common physiological mechanisms and may better represent adverse effects to chemotherapy compared to individual symptoms. We aimed to identify association between the experience of symptom clusters and specific genetic alterations. Methods: Study population consisted of 108 breast cancer patients who received over two cycles of adjuvant doxorubicin and cyclophosphamide (AC) treatment at the oncology institute of the Sheba Medical Center. Participants completed the Memorial Symptom Assessment Scale, the Lee Fatigue Scale and the Center for Epidemiological Studies Depression Scale. Hierarchical cluster analysis was used to identify patients' subgroups based on their symptom experience. For the genetic analyses, DNA was extracted from peripheral blood and single nucleotide polymorphisms (SNPs) of candidate genes were tested using restriction endonuclease assays. Results: Two distinct subgroups were identified based on severity of fatigue, depression, nausea, and change in food tastes: "all high" (n=79) and "all low" (n=29) level of all symptoms. As patients did not have active cancer, symptoms were attributed solely to chemotherapy. A genetic variant of HTR3C (rs6766410) results in a substitution of asparagine to lysine (N163K) may be associated with nausea and vomiting. We tested the association between this variant and symptom score. 51 of 75 (68%) patients with high symptom score harbored the variant allele, compared to 13 of 28 (46%) of those with low symptom score (p=0.038). Conclusions: Analysis of genetic background of clusters, rather than for individual symptoms, represents a novel approach for the study of chemotherapy-induced side effects. This approach enabled the identification of HTR3C variant as a possible mediator of side effects following treatment with AC. Discovering the genetic basis of symptom clusters may lead to the development of novel diagnostic and therapeutic modalities able to improve symptom management. This may translate to improved outcome among chemotherapy-treated cancer patients.