“Protect your warrior”: Safeguarding the catalytic destroyers of oncogenic microRNAs from rapid biological degradation

MicroRNA, ‘a small RNA molecule with a big mission’, has been recognised by the 2024 Nobel Prize award for its huge role as a master regulator of the expression of genes by inactivating the translation of messenger RNAs into proteins. When regulation by microRNAs becomes dysfunctional, serious diseases are triggered, including inflammatory diseases and aggressive forms of cancer. Indeed, excessive expression of “oncogenic” microRNAs are linked to human tumour transformations. Destroying these oncogenic miRNAs can reverse cell functions from “diseased” to “normal”. We have demonstrated specific and potent destruction of these oncogenic microRNAs in cells and tumours by a smart peptide–DNA molecule. We engineer the smart molecule as a catalyst to work like an enzyme, to bind and destroy many copies of target microRNA, by carefully linking a short piece of DNA (to recognise and bind particular microRNA sequences) to catalytic peptides (to breakdown the bound microRNA for recycling). Our smart catalysts work on their own, but crucially also work in synergy with the biological machinery inside cells to boost the speed of microRNA breakdown in cells and reduce their half-life by more than 150-times. This has put aggressive diseases within scope of our approach. Even the oncogenic microRNAs, which are rapidly produced in the most aggressive cancer cells, are knocked back down by these smart catalysts to reverse cells to their normal functions. A single dose of such peptide–DNA molecules was disease-modifying: it suppressed the malignant properties of cancer cells and inhibited tumour growth over weeks. However, these catalytic agents are rather unstable in cells and tissues, because the DNA used in our smart molecules (to recognise and bind harmful microRNAs) is degraded by cellular enzymes in body fluids within hours. The poor biological stability of these (currently unprotected) smart catalysts poses the main risk for transforming them into future therapies. In this project, we shall protect our microRNA-inactivating molecules from rapid biological degradation by shielding their most vulnerable parts with chemical alterations. This will make them resistant to cellular enzymes and increase their survival in the body considerably. We understand, of course, that any structural alterations may not only affect the “enzyme-like” properties of our smart catalyst, but also endanger its crucial synergy with cell machinery. It is important therefore that not only the biological stability in serum, but also both the catalytic and synergistic activities of the protected forms are measured in this project. Fortunately, we have years of extensive experience working with these microRNA-inactivating catalysts, which allowed us to find the best structural designs most likely to retain and even increase their “enzyme-like” action and synergy with cell machinery. Solving this “high-risk” factor (i.e., “biological instability”) will also boost the overall potency of the protected smart catalyst by increasing its survival time in body fluids, so that more of the dose reaches the target, and the knock-down continues to work for much longer to combat the rapid over-production of fresh microRNA in aggressive diseases with limited or no therapeutic solutions. Of many such unmet clinical needs, we chose knock-down of one of the most aggressive metastatic cancers (Triple-Negative Breast Cancer) as the demonstrator of success.