ABSTRACT: Breast cancer is the number one cause of death in women. Therefore, a method to detect early cancer by using biomarkers such as microRNA is needed. One of microRNAs that have important role in breast cancer development is miR-155. The expression of miR-155 is thought to target the expression of tumor suppressor mRNA SOCS1 that control cancer progression. This study aims to determine the of hsa-miR-155-5p and SOCS1 mRNA in blood plasma of breast cancer patients before and after chemotherapy. This research was conducted with sample of breast cancer patients blood plasma obtained from dr. Sardjito Hospital with a total sample of 64 samples. The methods are isolation of RNA using RNA Isolation Kit miRCURY-Biofluid. CDNA synthesis using cDNA Synthesis kit II, running with PCR thermal cycler (Biorad C1000) and the detection of the expression of HSA-miR-155-5p use ExiLent SYBR Green master mix (Exiqon) by using Real-time qPCR (Biorad CFX 96). SOCS1 mRNA was quantified by One-Step qRT-PCR KAPA SYBR kit. Both of qRT-PCR results then analyzed by Livak's and differences values were analyzed in T-test. The results obtained in this study that the expression of hsa-miR-155-5p in the plasma of breast cancer patients after chemotherapy has increased by 10.59 times higher than before chemotherapy (p = 0.001), SOCS1 mRNA expression in the plasma of breast cancer patients after chemotherapy decreased by 74.52 times lower than before chemotherapy (p = 0.001). The expression of hsa-miR-155-5p and SOCS1 mRNA had significant results (p <0.05) From this study we can conclude that there is upregulated expression of hsa-miR-155-5p and downregulated expression of mRNA SOCS1 after chemotherapy compare with before chemotherapy and also there is relationship between the expression of hsa-miR-155-5p as oncomir that targetting mRNA SOCS1 as tumor suppressor.
