Bioavailability enhancement of paclitaxel via a novel oral drug delivery system: paclitaxel-loaded glycyrrhizic acid micelles.

Paclitaxel (PTX, taxol), a classical antitumor drug against a wide range of tumors, shows poor oral bioavailability. In order to improve the oral bioavailability of PTX, glycyrrhizic acid (GA) was used as the carrier in this study. This was the first report on the preparation, characterization and the pharmacokinetic study in rats of PTX-loaded GA micelles The PTX-loaded micelles, prepared with ultrasonic dispersion method, displayed small particle sizes and spherical shapes. Differential scanning calorimeter (DSC) thermograms indicated that PTX was entrapped in the GA micelles and existed as an amorphous state. The encapsulation efficiency was about 90%, and the drug loading rate could reach up to 7.90%. PTX-loaded GA micelles displayed a delayed drug release compared to Taxol in the in vitro release experiment. In pharmacokinetic study via oral administration, the area under the plasma concentration-time curve (AUC0→24 h) of PTX-loaded GA micelles was about six times higher than that of Taxol (p < 0.05). The significant oral absorption enhancement of PTX from PTX-loaded GA micelles could be largely due to the increased absorption in jejunum and colon intestine. All these results suggested that GA would be a promising carrier for the oral delivery of PTX.

New application of an old drug: Antitumor activity and mechanisms of doxycycline in small cell lung cancer.

Small cell lung cancer (SCLC) remains one of the most aggressive tumors with a poor prognosis. The clinical outcome of SCLC patients has reached its plateau with the existing standard treatment and thus new therapies are urgently required. Accumulating evidences have indicated that doxycycline, a commonly used antibiotic, has antitumor activity against several malignancies. However, whether doxycycline has antitumor activity in SCLC and its underlying mechanisms remain unclear. Our investigation demonstrated that doxycycline could significantly inhibit the proliferation and colony formulation of SCLC cells (p<0.05). Furthermore, both Hoechst 33258 dye staining and TUNEL assays indicated that doxycycline could induce remarkable apoptosis of H446 cells in a concentration-dependent manner. RT-PCR and western blot assays proved that apoptosis induction effect of doxycycline was achieved via inducing the expression of caspase-3 and bax, as well as attenuating the expression of survivin and bcl-2. Moreover, the wound healing assay and Transwell assay indicated that doxycycline could significantly suppress the migration and invasion of H446 cells in a concentration-dependent manner (p<0.05). ELISA assay proved that the inhibitory effect of doxycycline on the migration and invasion of H446 cells was achieved via decreasing the secretion of MMP-2, MMP-9 and VEGF, as well as increasing the secretion of TIMP-2. Taken together, doxycycline dose-dependently suppressed the proliferation, colony formulation, migration and invasion of SCLC cells, as well as induced apoptosis. These findings encourage further investigations on the potential of doxycycline as a candidate drug for the treatment of SCLC.

Afatinib reverses multidrug resistance in ovarian cancer via dually inhibiting ATP binding cassette subfamily B member 1.

ABCB1-mediated multidrug resistance (MDR) remains a major obstacle to successful chemotherapy in ovarian cancer. Herein, afatinib at nontoxic concentrations significantly reversed ABCB1-mediated MDR in ovarian cancer cells in vitro (p < 0.05). Combining paclitaxel and afatinib caused tumor regressions and tumor necrosis in A2780T xenografts in vivo. More interestingly, unlike reversible TKIs, afatinib had a distinctive dual-mode action. Afatinib not only inhibited the efflux function of ABCB1, but also attenuated its expression transcriptionally via down-regulation of PI3K/AKT and MAPK/p38-dependent activation of NF-κB. Furthermore, apart from a substrate binding domain, afatinib could also bind to an ATP binding domain of ABCB1 through forming hydrogen bonds with Gly533, Gly534, Lys536 and Ala560 sites. Importantly, mutations in these four binding sites of ABCB1 and the tyrosine kinase domain of EGFR were not correlated with the reversal activity of afatinib on MDR. Given that afatinib is a clinically approved drug, our results suggest combining afatinib with chemotherapeutic drugs in ovarian cancer. This study can facilitate the rediscovery of superior MDR reversal agents from molecular targeted drugs to provide a more effective and safer way of resensitizing MDR.