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Simple Summary: Lynch syndrome is an autosomal dominant hereditary disease that confers a high risk of developing various types of tumors, especially colorectal and endometrial cancer. In recent years, the molecular mechanisms underlying Lynch syndrome have generated considerable interest. Several studies have highlighted the epiphenomenon of microsatellite instability, caused by a deficit in the ability of cells to repair DNA damage, as a disease-specific feature. The discovery of microRNAs has served to clarify how these small oligonucleotide molecules may contribute to the progression of Lynch syndrome by modulating the expression of several players involved in DNA repair pathways. The purpose of this review is to analyze the management of patients with Lynch syndrome by emphasizing the importance of microRNAs as markers or therapeutics for the development of novel clinical approaches. Lynch syndrome (LS), also known as Hereditary Non-Polyposis Colorectal Cancer (HNPCC), is an autosomal dominant cancer syndrome which causes about 2–3% of cases of colorectal carcinoma. The development of LS is due to the genetic and epigenetic inactivation of genes involved in the DNA mismatch repair (MMR) system, causing an epiphenomenon known as microsatellite instability (MSI). Despite the fact that the genetics of the vast majority of MSI-positive (MSI+) cancers can be explained, the etiology of this specific subset is still poorly understood. As a possible new mechanism, it has been recently demonstrated that the overexpression of certain microRNAs (miRNAs, miRs), such as miR-155, miR-21, miR-137, can induce MSI or modulate the expression of the genes involved in LS pathogenesis. MiRNAs are small RNA molecules that regulate gene expression at the post-transcriptional level by playing a critical role in the modulation of key oncogenic pathways. Increasing evidence of the link between MSI and miRNAs in LS prompted a deeper investigation into the miRNome involved in these diseases. In this regard, in this study, we discuss the emerging role of miRNAs as crucial players in the onset and progression of LS as well as their potential use as disease biomarkers and therapeutic targets in the current view of precision medicine. [ABSTRACT FROM AUTHOR]

Simple Summary: DNA-damage repair (DDR) gene alterations are a hallmark for cancer. The exploitation of DDR alterations has improved outcomes in breast, ovarian, pancreatic, and prostate cancers. However, little is known about the role of DDR alterations, leading to a homologous recombination deficiency (HRD) state in lung cancer. In this review, we discuss the existing literature examining the role of DDR alterations as both predictive biomarkers of response to therapy and as therapeutic targets in lung cancer. Lung cancer remains the second most commonly diagnosed cancer worldwide and the leading cause of cancer-related mortality. The mapping of genomic alterations and their role in lung-cancer progression has been followed by the development of new therapeutic options. Several novel drugs, such as targeted therapy and immunotherapy, have significantly improved outcomes. However, many patients with lung cancer do not benefit from existing therapies or develop progressive disease, leading to increased morbidity and mortality despite initial responses to treatment. Alterations in DNA-damage repair (DDR) genes represent a cancer hallmark that impairs a cell's ability to prevent deleterious mutation accumulation and repair. These alterations have recently emerged as a therapeutic target in breast, ovarian, prostate, and pancreatic cancers. The role of DDR alterations remains largely unknown in lung cancer. Nevertheless, recent research efforts have highlighted a potential role of some DDR alterations as predictive biomarkers of response to treatment. Despite the failure of PARP inhibitors (main class of DDR targeting agents) to improve outcomes in lung cancer patients, there is some evidence suggesting a role of PARP inhibitors and other DDR targeting agents in benefiting a distinct subset of lung cancer patients. In this review, we will discuss the existing literature on DDR alterations and homologous recombination deficiency (HRD) state as predictive biomarkers and therapeutic targets in both non-small cell lung and small cell lung cancer. [ABSTRACT FROM AUTHOR]