PTEN and Organ-Specific microRNAs in Metastatic Breast Cancer

Breast cancer is a heterogeneous disease with varying biological behaviors and a strong tendency to metastasize to specific organs, including the bone, liver, lung, and brain. The development of distant metastases remains the primary cause of breast cancer-related mortality. Therefore, the identification of reliable, minimally invasive biomarkers that can predict metastatic spread is a critical unmet clinical need. MicroRNAs (miRNAs) are small, noncoding RNA molecules that regulate gene expression and have emerged as promising biomarkers due to their stability in the circulation and their association with cancer progression. Specific miRNA expression patterns have been linked to organotropism in breast cancer, including signatures associated with bone, lung, liver, and brain metastases. Additionally, PTEN is a key tumor suppressor gene involved in cell cycle regulation, apoptosis, and PI3K/AKT pathway signaling. Loss of PTEN function is frequently observed in aggressive and metastatic breast cancers, and reduced circulating PTEN levels may correlate with tumor burden and metastatic dissemination. This prospective observational clinical study aims to evaluate serum PTEN levels and organ-specific miRNA profiles in three participant groups: Metastatic breast cancer patients (n=80) diagnosed with distant organ involvement. Early-stage non-metastatic breast cancer patients (n=40) with no radiological or clinical evidence of metastasis. Healthy control participants (n=40) without known malignancy. Serum samples will undergo laboratory analysis using two validated molecular techniques: Quantitative reverse transcription polymerase chain reaction (qRT-PCR) for profiling selected miRNAs associated with organ-specific metastatic patterns. Enzyme-linked immunosorbent assay (ELISA) for quantification of circulating PTEN protein levels. The primary objective of the study is to compare serum PTEN and miRNA expression levels between metastatic and non-metastatic breast cancer groups, as well as healthy controls. Secondary objectives include assessing associations between these biomarkers and (a) the number of metastatic sites, (b) specific organ involvement (bone, lung, liver, brain), and (c) selected clinical characteristics, including hormone receptor status, HER2 expression, patient age, and stage at diagnosis. The overarching goal is to characterize a panel of circulating biomarkers that may contribute to early detection of metastatic potential and organ-specific metastatic patterns in breast cancer. Identifying such signatures may facilitate noninvasive risk stratification, support personalized treatment planning, and form the basis for future translational research aimed at developing clinically applicable diagnostic assay