**4. Role of miRNAs in ovarian cancer**

miRNAs are single-stranded RNA nucleotides that regulate gene expression. In the human body, they are reported to be involved in regulating around 60% of genes affecting various cellular and biological processes. Each miRNA has multiple gene targets or multiple miRNAs can act on one target gene. They can function either as an oncogene or a tumor suppressor and their expressions in cancer cells are deregulated [136]. The miRNA expression profile for each OC subtype is reported to be distinct, with a subset of miRNAs downregulated or upregulated [137]. The miRNA signatures identified in various cancer types are being investigated for their utility as cancer biomarkers in tumor diagnosis, prognosis and therapeutic outcome.


### **Table 4.**

*Deregulated miRNAs in ovarian cancer subtypes.*

The sensitivity of a cancer drug profoundly affects treatment efficacy and prognosis. miRNAs are involved in conferring chemo-sensitive or chemoresistant phenotype by regulating the drug-resistance related genes [138]. Therefore, manipulating the expression levels of specific miRNAs can aid in drug sensitivity. As previously mentioned, the sensitivity for platinum drugs varies among each OC subtype, and this profoundly affects the treatment efficacy and prognosis. Though still in its infancy, targeting miRNA holds great promise for a more customized therapeutic approach. Here, we highlight the key miRNAs reported in recent literature, which are deregulated in the various OC subtypes (**Table 4**).
