The Role of Four Circulating MicroRNAs as Prognostic Biomarkers for Non Small Cell Lung Cancer in Lebanese Patients

Abstract

Introduction: Globally, lung cancer (LC) is the primary cause of cancer morbidity and mortality. It is divided into 2 types: Small Cell Lung Cancer (SCLC), which accounts for 15% of cases, and Non-Small Cell Lung Cancer (NSCLC), which accounts for 85% of cases. The main issue with LC is that it is an asymptomatic disease in its early stages. This leads to missed early diagnosis, treatment, and eventually poor prognosis in patients. This highlights the need for non-invasive prognostic biomarkers to help precisely predict disease progression and enhance individualized treatment plans, due to late diagnosis. Biomarkers are defined as quantifiable biological molecules found in the blood or other body fluids that reflect whether the body is in a normal or pathological state and can predict disease progression and response to treatment. miRNAs, which are small non-coding RNAs, are examples of biomarkers. In cancer, they are usually secreted by the tumor into the circulation. Research highlights that specific miRNAs are frequently dysregulated in LC, whereby they contribute to tumor progression and resistance to treatment. However, no such studies have been done in Lebanon, and there is limited data on circulating miRNAs in NSCLC, especially concerning prognosis.

Aims: This study aims to investigate the prognostic value of four candidate circulating miRNAs: miR-21-5p, miR-155-5p, miR-205-5p, and miR-126, in the serum of stage IV Lebanese NSCLC patients.

Methods: This study builds on an Institutional Review Board (IRB)-approved cohort comprising newly diagnosed LC patients (IM.AT1.23). A total of 49 NSCLC patients were selected, all presenting with stage IV disease and undergoing therapy. Candidate miRNAs were selected following an extensive literature review. Total RNA was isolated from serum samples and reverse transcribed. miRNA expression levels were quantified by real-time PCR. UniSp6 was used as an endogenous control. The ΔCt method was used to quantify the expression level of the miRNAs. For data analysis, the Mann-Whitney U test was conducted to compare expression levels between patients with long and short Progression-free survival (PFS) durations (≤6 months and > 6 months), and Kaplan-Meier survival analysis was conducted to compare differences in PFS based on high versus low miRNA expression.

Results: There was no significant association between the expression of the four circulating miRNAs (miR-21, miR-155, miR-205, and miR-126) and the PFS duration (≤6 months and > 6 months). Similarly, Kaplan-Meier analysis showed no statistical differences between PFS and high versus low expression of all four candidate miRNAs.

Conclusion: To our knowledge, this study is the first to investigate the prognostic potential of circulating miR-21, miR-155, miR-205, and miR-126 in Lebanese NSCLC patients. The results showed that the expression of the four miRNAs is not statistically associated with PFS, indicating that they cannot serve as prognostic biomarkers in this cohort. The small sample size may have decreased the statistical power. Further experiments done on a larger cohort, including more dysregulated miRNAs, and studying different clinical endpoints, might yield statistically significant results, making circulating miRNAs valuable prognostic biomarkers.