Promoter hypermethylation of RARB and GSTP1 genes in plasma cell-free DNA as breast cancer biomarkers in Peruvian women.

BACKGROUND: Promoter hypermethylation is one of the enabling mechanisms of hallmarks of cancer. Tumor suppressor genes like RARB and GSTP1 have been reported as hypermethylated in breast cancer tumors compared with normal tissues in several populations. This case-control study aimed to determine the association between the promoter methylation ratio (PMR) of RARB and GSTP1 genes (separately and as a group) with breast cancer and its clinical-pathological variables in Peruvian patients, using a liquid biopsy approach. METHODS: A total of 58 breast cancer patients and 58 healthy controls, matched by age, participated in the study. We exacted cell-free DNA (cfDNA) from blood plasma and converted it by bisulfite salts. Methylight PCR was performed to obtain the PMR value of the studied genes. We determined the association between PMR and breast cancer, in addition to other clinicopathological variables. The sensitivity and specificity of the PMR of these genes were obtained. RESULTS: A significant association was not found between breast cancer and the RARB PMR (OR = 1.90; 95% CI [0.62-6.18]; p = 0.210) or the GSTP1 PMR (OR = 6.57; 95% CI [0.75-307.66]; p = 0.114). The combination of the RARB + GSTP1 PMR was associated with breast cancer (OR = 2.81; 95% CI [1.02-8.22]; p = 0.026), controls under 50 years old (p = 0.048), patients older than 50 (p = 0.007), and postmenopausal (p = 0.034). The PMR of both genes showed a specificity of 86.21% and a sensitivity of 31.03%. CONCLUSION: Promoter hypermethylation of RARB + GSTP1 genes is associated with breast cancer, older age, and postmenopausal Peruvian patients. The methylated promoter of the RARB + GSTP1 genes needs further validation to be used as a biomarker for liquid biopsy and as a recommendation criterion for additional tests in asymptomatic women younger than 50 years.

Patrones clínicos de los tumores de mama de acuerdo a su fenotipo en la población peruana / Clinical patterns of breast tumors according to their phenotype in the Peruvian population

Introducción: La clasificación de los tumores de mama estuvo basada en características histológicas, mientras que variables clinicopatológicos eran usadas como factores predictivos del curso clínico de la enfermedad. Los estudios de los perfiles genéticos consiguieron una clasificación molecular mucho más exacta. El objetivo de este estudio fue evaluar los patrones clínicos y de recurrencia de los tumores de mama de acuerdo a su fenotipo determinado por inmunohistoquímica. Material y métodos:Evaluamos un cohorte de 1044 pacientes diagnosticados con cáncer de mama operable entre los años 2000-2002 diagnosticados y tratados en el Instituto Nacional de Enfermedades Neoplásicas. Los fenotipos fueron caracterizado por inmunohistoquímica en [RE+ y/o RP+, HER2+], triple negativo [RE-, RP-, HER2-] y HER2+ [HER2+, sin importar el estado de los receptores hormonales]. Se evaluó la significancia pronóstica del fenotipo. Resultados: En nuestros casos, el 519 (49.7%) presentaron tumores [RE+ y/o RP+, HER2-], 212 (20.3%) presentaron tumores triple negativo y 313 (30.0%) presentaron tumores HER2+. El 23.2% (242) de los casos presentaron recurrencia local o a distancia y el 22.5% (235) fallecieron. El fenotipo [RE+ y/o RP+, HER2+] mostró una frecuencia más elevada de metástasis ósea (38.9%), seguido del fenotipo HER2 (27.2%) y triple negativo(23.6%). El fenotipo triple negativo mostró una baja tendencia a producir metástasis hepática (1.8%) comparado con [RE+ y/o RP+, HER2+] y HER2+ (21.1% y 19.6%, respectivamente). Se encontraron diferencias entre fenotipos en la sobrevida libre de enfermedad (P=0.001) y sobrevida global (P=0.005) los riesgos relativos de recurrencia y muerte fueron tiempo dependientes. Conclusiones: El fenotipo triple negativo y HER2+ se comportan como tumores altamente agresivos. La determinación del fenotipo por inmunohistoquímica es una excelente herramienta del pronóstico del curso de la enfermedad.

Introduction: The classification of breast tumors was based on histologic features, while clinicopa-thologic variables were used as predictors of clinical course of the disease. Studies of genetic profiles obtained a more accurate molecular classification. The objective of this study was to evaluate the clinical patterns and recurrence of breast tumors according to their phenotype determined by immunohistochemistry. Material and methods: We evaluated a cohort of 1044 patients diagnosed with operable breast cancer diagnosed between 2000-2002 and treated at the Instituto Nacional de Enfermedades Neo-plasicas. The phenotypes were characterized by immunohistochemistry in [ER + and / or PR +, HER2+], triple negative [ER-, PR-, HER2-] and HER2 + [HER2 +, regardless of the status of hormone recep-tors]. We assessed significant prognostic phenotype. Results: In our cases, 519 (49.7%) had tumors [ER + and / or PR +, HER2-], 212 (20.3%) had triple-negative tumors and 313 (30.0%) had HER2 + tumors. 23.2% (242) of cases had local or distant recurrence and 22.5% (235) died. The phenotype [ER + and / or PR +, HER2 +] showed a higher frequency of bone metastasis (38.9%), followed by HER2 phenotype (27.2%) and triple negative (23.6%). The triple negative phenotype showed a low tendency to produce liver metastases (1.8%) compared with [ER + and / or PR +, HER2 +] and HER2 + (21.1% and 19.6%, respectively). Differences were found between phenotypes in disease free survival (P = 0.001) and overall survival (P = 0.005) relative risks of recurrence and death were time dependent. Conclusions: Triple negative phenotype and HER2 + tumors behave as highly aggressive. The determination of the phenotype by immunohistochemistry is an excellent tool for predicting the course of the disease.