pH-responsive targeted gold nanoparticles for in vivo photoacoustic imaging of tumor microenvironments.

The acidic microenvironment of tumor tissues has been proven to be a major characteristic for differentiation from normal tissues, thereby providing a desirable target for both disease diagnosis and functional imaging. We herein introduce a way to endow gold nanoparticles with aggregation behaviour induced by pH tuning. The nanoparticle surface was modified with two thiol conjugate molecules, which could smartly stabilize it at the pH of blood and normal tissues but induce aggregation in response to the acidic extracellular pH in tumor. The surface conjugate molecule composition effect was studied systematically, and at the optimal surface conjugate molecule composition, a pH-responsive active tumor-targeting c(RGDyk)-MHDA/LSC@AuNP nanoprobe was successfully obtained and showed a significantly enhanced contrast effect for both in vitro and in vivo photoacoustic (PA) imaging. Intravenous administration of our nanoprobe to U87MG tumor-bearing nude mice showed PA imaging contrasts almost 3-fold higher than those for the blocking group. Quantitative biodistribution data revealed that 9.7 µg g-1 of nanoprobe accumulated in the U87MG tumor 4 h post-injection. These findings might provide an effective strategy for developing new classes of intelligent and biocompatible contrast agents with a high efficiency for PA imaging and PA imaging-guided cancer therapy.

The cycloartane triterpenoid ADCX impairs autophagic degradation through Akt overactivation and promotes apoptotic cell death in multidrug-resistant HepG2/ADM cells.

Multidrug resistance is the main obstacle in cancer chemotherapy. Emerging evidence demonstrates the important role of autophagy in cancer cell resistance to chemotherapy. Therefore, autophagy inhibition by natural compounds may be a promising strategy for overcoming drug resistance in liver cancer cells. Here, we found that ADCX, a natural cycloartane triterpenoid extracted from the traditional Chinese medicine (TCM) source Cimicifugae rhizoma (Shengma), impaired autophagic degradation by suppressing lysosomal cathepsin B (CTSB) expression in multidrug-resistant liver cancer HepG2/ADM cells, thereby leading to autophagic flux inhibition. Moreover, impairing autophagic flux promoted ADCX-induced apoptotic cell death in HepG2/ADM cells. Interestingly, Akt was overactivated by ADCX treatment, which downregulated CTSB and inhibited autophagic flux. Together, our results provide the first demonstration that an active TCM constituent can overcome multidrug resistance in liver cancer cells via Akt-mediated inhibition of autophagic degradation.

Oleanolic acid isolated from Oldenlandia diffusa exhibits a unique growth inhibitory effect against ras-transformed fibroblasts.

AIMS: Oldenlandia diffusa (Willd.) Roxb. (O. diffusa) is a commonly used traditional Chinese medicine for treating cancer. Its pharmacological activities and anti-cancer effects have been the focus of intense research in recent years. In the present study, we aim to investigate whether the five major compounds from O. diffusa possess a unique inhibitory activity against ras-transformed cells in a well-established cell model. MAIN METHODS: The anti-cancer effects of O. diffusa were assessed in a co-culture system containing normal and transformed Rat 6 (R6) fibroblasts. In addition, a transwell assay was used to examine the interaction between the drugs and the co-cultivated cells. KEY FINDINGS: Our data showed that among the samples tested, oleanolic acid (OA), but not the structural isomer ursolic acid (UA), inhibits the growth of ras oncogene-transformed R6 cells at a dosage that is not toxic to the co-cultivated normal fibroblasts. A significant inhibitory effect was also observed in the transwell experiments, indicating that the mode of action for OA-mediated growth inhibition of transformed cells does not require direct cell-to-cell contact between normal and ras-transformed cells. Data obtained from experiments conducted with the conditioned medium that was collected from normal R6 cells treated with OA also suggest that OA might cause normal cells to secrete inhibitory factor(s) against the transformed cells. The enhanced ability of OA to cause cytotoxicity in transformed cells in the presence of normal fibroblasts is also observed with the human hepatocellular carcinoma cell line, SMMC-7721. SIGNIFICANCE: The present study demonstrates that OA may possess both cancer chemotherapeutic and chemopreventive activities. Thus, it may have great potential for clinical application as a novel anti-cancer drug.