Exosome RNA Exosome RNA Research & Industry News
Ovarian cancer (OvCa) is a challenging disease to treat, and despite advances in cancer immunotherapy, its success has been limited. One of the key hurdles is the tumor microenvironment (TME), which is immunosuppressive and prevents effective immune responses. Within this environment, tumor-associated macrophages (TAMs) play a significant role in promoting tumor growth, resistance to chemotherapy, and even metastasis. These macrophages are not just bystanders in cancer progression; they actively support the tumor by creating a protective, immune-suppressive environment. Researchers are now looking for innovative ways to reprogram these TAMs to act against the tumor, and one promising approach involves the use of microRNAs (miRNAs).
MiRNAs are small RNA molecules that regulate gene expression by silencing specific target genes. It turns out that TAMs in ovarian cancer display distinct miRNA profiles that influence their behavior. By delivering the right miRNAs to these macrophages, scientists aim to shift their phenotype from a pro-tumor to an anti-tumor state, which could enhance the effectiveness of cancer immunotherapies.
Oncolytic viruses (OVs) are viruses that specifically target and kill cancer cells. These viruses can be genetically engineered to deliver therapeutic agents, making them an exciting tool for cancer treatment. Researchers have recently discovered that OVs can be used to deliver miRNAs to the TME, particularly to TAMs, by packaging these miRNAs into tumor-derived extracellular vesicles (TDEVs). These vesicles are small particles released by tumor cells, and OVs can increase their release, allowing miRNAs to spread throughout the tumor and impact the immune cells within.
In this study, researchers at the University of Leeds have identified two miRNAs—miR-155 and miR-19a—that play crucial roles in regulating TAM function. MiR-155 has been linked to promoting an anti-tumor immune response, while miR-19a is associated with a more pro-tumor state. The researchers used an oncolytic rhabdovirus (ORV) to deliver these miRNAs into ovarian cancer cells. The virus not only increased the production of TDEVs containing these miRNAs but also showed that these vesicles were efficiently taken up by TAMs.
Schematic of overall proposed mechanism of action of ORV-miRNA
Following infection of tumour cells with ORV-miRNA, extracellular vesicles are released containing miRNA (TDEV-miRNA), followed by lysis of the tumour cells (oncolysis). Concurrently, TDEV-miRNA are taken up by tumour associated macrophages and are reprogrammed into a less suppressive, inflammatory (anti-tumour) phenotype, the exact mechanism of this altered gene expression is still under investigation. Critically, oncolysis together with TDEV-miRNA release reduces tumour burden and enhances anti-tumour immune responses in ID8 bearing animals.
Through small RNA sequencing, the study identified a collection of miRNAs that were upregulated in TAMs with an anti-tumor phenotype, including miR-155. In contrast, miR-19a was downregulated during the differentiation of TAMs into a pro-tumor state. When TAMs were exposed to TDEVs expressing either miR-155 or miR-19a, their immunosuppressive activity was reversed, suggesting that these miRNAs could reprogram TAMs to support an immune response against the tumor.
The results showed that while both miR-155 and miR-19a had promising effects, the combination of the oncolytic virus and miR-155 was particularly effective in boosting the generation of anti-tumor T cells. Furthermore, miR-19a improved the survival of mice with ovarian tumors, highlighting its therapeutic potential.
This study offers a compelling example of how oncolytic viruses can be leveraged to deliver miRNAs to specific immune cells in the tumor microenvironment, potentially improving the efficacy of cancer immunotherapies. By reprogramming TAMs to adopt an anti-tumor role, these researchers are unlocking new avenues to overcome the immune evasion strategies employed by ovarian cancer, bringing hope for more effective treatments.
