UC Davis

Lung cancer remains the leading cause of cancer-related deaths among both men and women in the United States and worldwide with 80% of cases classified as Non-Small Cell Lung Cancer (NSCLC). While significant advancements have been made in cancer biology and therapies, overall survival of NSCLC patients remains one of the lowest among all cancer types. Therefore, the need for novel therapeutics to combat NSCLC is in high demand. RNA interfering (RNAi) provides researchers with a versatile and powerful tool for basic genetic and biomedical research and advancements in RNAi technologies have also introduced a novel, growing class of RNAi therapeutics into the clinic practice. By examining the six RNAi drugs, namely small interfering RNAs, being approved by the FDA, we revealed their overlapping characteristics with functional microRNAs (miRNAs or miRs) derived from the genome. With improved understanding of roles of miRNAs in NSCLC, replacement therapy may provide a novel route to reintroduce target tumor suppressive miRNAs found depleted in tumors to improve NSCLC therapy. Regrettably, current miRNA studies typically use chemically synthesized and modified miRNA mimics that might not truly represent the physicochemical and biological properties of natural miRNAs. To address this concern, our laboratory has developed an in vivo fermentation based platform technology to offer bioengineered RNAi agents (BioRNA). Using our BioRNA technology, we have successfully produced a panel of 48 novel BioRNAs, among them the BioRNAGly and BioRNALeu panels showed comparable overall yields, purities, and antiproliferative activities against NSCLC cells. Noticing miR-7-5p (miR-7) one of the most effective miRNAs, we further found that BioRNAGly/miR-7 (termed BioRNA/miR-7) offered higher levels of mature miR-7-5p to regulate the expression known targets, namely EGFR, MRP1, and VDAC1, with comparable or slightly greater activities compared with a commercial miR-7-5p mimic.

Indeed, miR-7 is a known tumor suppressive miRNA regulating some target genes important in metabolism, whereas it is commonly found with low levels of expression in NSCLC. Moreover, repression of efflux transporter MRP1 by miR-7 may be implicated in sensitizing NSCLC cells by increasing intracellular drug accumulation. Therefore, we aim to define the impact of miR-7 on NSCLC cell metabolism and anticancer activity of a co-administered small molecule drug. First, we identified the impact of BioRNA/miR-7 on mitochondrial EGFR expression along with two additionally known mitochondrial targets, namely SLC25A37 and TIM50, in NSCLC cells, leading to an abnormal, condensed mitochondria morphology. Second, we validated a new and direct target for miR-7, mitochondrial AGK, and observed a reduction of mitochondrial respiration and glycolytic capacity by BioRNA/miR-7. Further, we revealed a synergism for co-administered pemetrexed (PEM) to inhibit NSCLC growth, accompanied by a sharp increase in intracellular PEM levels. Moreover, we demonstrated the effectiveness of BioRNA/miR-7, alone and combined with PEM, to control tumor growth in a NSCLC patient-derived xenograft mouse model.

Thus, we have identified BioRNA/miR-7 from a set of BioRNAs as a potential anticancer agent that functions through endogenous RNAi mechanisms to disrupt NSCLC cell metabolism and MRP1-mediated drug efflux. Together, our collective works demonstrate a widening role for miR-7 in NSCLC biology and supports the use of miR-7 to improve current therapeutics for NSCLC.