miR-145-3p subexpression, life habits and comorbidities in cholangiocarcinoma carcinogenesis pathway

Cholangiocarcinoma (CCA) is a malignant tumor that originates from cholangiocytes, epithelial cells of the bile ducts. It can be classified, according to the anatomical location, as intrahepatic (iCCA) or extrahepatic (eCCA). Although it is associated with inflammatory liver diseases, advanced age, diabetes, obesity, infectious agents, alcohol, drugs, and smoking, its etiology is often unknown. Angiogenesis, the formation of new blood vessels from existing vessels, is a process of great importance related to carcinogenesis. On this basis, microRNAs (miRNA), endogenous non-coding RNAs whose primary function is to control gene expression at the post-transcriptional level, inhibiting the expression of target mRNA, are associated with crucial factors of angiogenesis, such as vascular endothelial growth factor (VEGF) A, an isoform of VEGF and the main mediator of hypoxia-induced tumor growth. Thus, miR-145-3p, which acts on the VEGF gene, is underexpressed in several types of cancer, including breast, prostate, and lung cancer, in conditions of hypoxia and iCCA. Furthermore, miRNAs may show changes in their expression in smokers, compared to those who never smoked, as well as there are miRNAs with overexpression related to increased serum levels of high-density lipoprotein, low-density lipoprotein, and triglycerides. This study evaluated miR-145-3p expression in patients with CCA and its association with lifestyle, comorbidities, tumor size and subtypes, and the discriminatory potential of miR-145-3p expression with tumor subtypes. Sixty-six individuals were studied, distributed into: Study Group (SG) – 66 patients with CCA (median age=59 years; 50% female); Control Group (CG) – 30 individuals without CCA, undergoing gallbladder removal surgery (median age=45 years; 76,6% female). RNA was extracted from paraffined tumor tissue (SG) and cystic duct sample (CG). The miR-145 expression was analyzed by real-time polymerase chain reaction. Life habits - smoking and alcoholism - and comorbidities – diabetes mellitus (DM), systemic arterial hypertension (SAH) and body mass index (BMI≥25kg/m2) – were obtained through medical questionnaires and records. The admitted alpha error was 5%. There was a decrease in miR-145-3p expression in patients compared to controls (median=0.22; P < 0.0001). For lifestyle habits, smoking prevailed in the SG (47.5%; P=0.004), while alcohol consumption was similar between groups. Alcoholism, DM, SAH, BMI, size and tumor subtype were not associated with miR-145-3p expression. The analysis of the discriminatory potential of miR-145-3p expression showed an area under the curve (AUC) of 0.41 (0.25 – 0.57) with 73.3% sensitivity and 47.6% specificity for a ≤0.415 cutoff. Logistic regression analysis to identify independent factors showed that patients with CCA are 11 times more likely to be smokers (odds ratio=11.207; P=0.013). miR-145-3p underexpression and smoking are associated with CCA. The reduced expression of this microRNA can modulate mechanisms involved in the CCA carcinogenesis pathway, highlighting smoking as a factor related to the disease.