Hepatocellular carcinoma (HCC) is the second leading cause of cancer deaths worldwide largely due to lack of effective targeted drugs to simultaneously block multiple cancer-driving pathways. The identification of all-trans retinoic acid (ATRA) as a potent Pin1 inhibitor provides a promising candidate for HCC targeted therapy because Pin1 is overexpressed in most HCC and activates numerous cancer-driving pathways. However, the efficacy of ATRA against solid tumors is limited due to its short half-life of 45min in humans. A slow-releasing ATRA formulation inhibits solid tumors such as HCC, but can be used only in animals. Here, we developed a one-step, cost-effective route to produce a novel biocompatible, biodegradable, and non-toxic controlled release formulation of ATRA for effective HCC therapy. We used supercritical carbon dioxide process to encapsulate ATRA in largely uniform poly L-lactic acid (PLLA) microparticles, with the efficiency of 91.4% and yield of 68.3%, and ~4-fold higher C and AUC over the slow-releasing ATRA formulation. ATRA-PLLA microparticles had good biocompatibility, and significantly enhanced the inhibitory potency of ATRA on HCC cell growth, improving IC by over 3-fold. ATRA-PLLA microparticles exerted its efficacy likely through degrading Pin1 and inhibiting multiple Pin1-regulated cancer pathways and cell cycle progression. Indeed, Pin1 knock-down abolished ATRA inhibitory effects on HCC cells and ATRA-PLLA did not inhibit normal liver cells, as expected because ATRA selectively inhibits active Pin1 in cancer cells. Moreover ATRA-PLLA microparticles significantly enhanced the efficacy of ATRA against HCC tumor growth in mice through reducing Pin1, with a better potency than the slow-releasing ATRA formulation, consistent with its improved pharmacokinetic profiles. This study illustrates an effective platform to produce controlled release formulation of anti-cancer drugs, and ATRA-PLLA microparticles might be a promising targeted drug for HCC therapy as PLLA is biocompatible, biodegradable and nontoxic to humans.

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To solve the problem of synthesized magnetic nanoparticles in cancer therapy, a new drug delivery system synthesized from bacteria was used to load cytosine arabinoside (Ara-C). Genipin (GP) and poly- l -glutamic acid (PLGA) were selected as dual cross-linkers. The preparation and characterization of Ara-C-loaded GP-PLGA-modified bacterial magnetosomes (BMs) (ABMs-P), as well as their in vitro antitumor effects, were all investigated. Transmission electron micrographs (TEM) and Fourier transform infrared (FTIR) spectroscopy suggested that Ara-C could be bound to the membrane of BMs modified by GP-PLGA. The diameters of the BMs and ABMs-P were 42.0±8.6 nm and 74.9±8.2 nm, respectively. The zeta potential revealed that the nanoparticles were stable. Moreover, this system exhibited optimal drug-loading properties and long-term release behavior. The optimal encapsulation efficiency and drug-loading were 64.1%±6.6% and 38.9%±2.4%, respectively, and ABMs-P could effectively release 90% Ara-C within 40 days, without the release of an initial burst. In addition, in vitro antitumor experiments elucidated that ABMs-P is cytotoxic to HL-60 cell lines, with an inhibition rate of 95%. The method of coupling drugs on BMs using dual cross-linkers is effective, and our results reveal that this new system has potential applications for drug delivery in the future.

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