RHAMM-mediated bifunctional nanotherapy targeting Bcl-xL and mitochondria for pancreatic neuroendocrine tumor treatment.

The incidence of pancreatic neuroendocrine tumor (PNET) has continued to rise. Due to their indolent feature, PNET patients often present with incurable, metastatic diseases. Novel therapies are urgently needed. We have previously shown that Receptor for Hyaluronic Acid-Mediated Motility isoform B (RHAMM) and Bcl-xL are upregulated in PNETs and both of them promote PNET metastasis. Because RHAMM protein is undetectable in most adult tissues, we hypothesized that RHAMM could be a gateway for nanomedicine delivery into PNETs. To test this, we developed a RHAMM-targeting nanoparticle (NP). Inside this NP, we assembled small interfering RNA (siRNA) against Bcl-xL (siBcl-xL) and mitochondria-fusing peptide KLA. We demonstrated that RHAMM-positive PNETs picked up the RHAMM-targeting NPs. siBcl-xL or KLA alone killed only 30% of PNET cells. In contrast, a synergistic killing effect was achieved with the co-delivery of siBcl-xL and KLA peptide . Unexpectedly, siBcl-xL induced cell death before reducing Bcl-xL protein levels. The systemically injected RHAMM-targeting NPs carrying siBcl-xL and KLA peptide significantly reduced tumor burden in mice bearing RHAMM-positive PNETs. Together, these findings indicate that the RHAMM-targeting nanotherapy serves as a promising drug delivery system for PNET and possibly other malignancies with upregulated RHAMM. The combination of siBcl-xL and KLA peptide can be a therapy for PNET treatment.