MYO10-filopodia support basement membranes at pre-invasive tumor boundaries.

Ductal carcinoma in situ (DCIS) is a pre-invasive stage of breast cancer. During invasion, the encapsulating DCIS basement membrane (BM) is compromised, and tumor cells invade the surrounding stroma. The mechanisms that regulate functional epithelial BMs in vivo are poorly understood. Myosin-X (MYO10) is a filopodia-inducing protein associated with metastasis and poor clinical outcome in invasive breast cancer (IBC). We identify elevated MYO10 expression in human DCIS and IBC, and this suggests links with disease progression. MYO10 promotes filopodia formation and cell invasion in vitro and cancer-cell dissemination from progressively invasive human DCIS xenografts. However, MYO10-depleted xenografts are more invasive. These lesions exhibit compromised BMs, poorly defined borders, and increased cancer-cell dispersal and EMT-marker-positive cells. In addition, cancer spheroids are dependent on MYO10-filopodia to generate a near-continuous extracellular matrix boundary. Thus, MYO10 is protective in early-stage breast cancer, correlating with tumor-limiting BMs, and pro-invasive at later stages, facilitating cancer-cell dissemination.

Design, synthesis and biological evaluation of quinoline-2-carbonitrile-based hydroxamic acids as dual tubulin polymerization and histone deacetylases inhibitors.

A series of quinoline and quinazoline analogs were designed and synthesized as new tubulin polymerization (TP) and histone deacetylases (HDAC) inhibitors. Compounds 12a and 12d showed the best cytotoxicity activities against a panel of human cancer cell lines with an averaged IC50 value of 0.6 and 0.7 nM, respectively. Furthermore, these lead compounds showed good activities against CA-4-resistant colon-carcinoma and multidrug-resistant leukemia cells. In addition, compounds 12a and 12d induced HT29 cell cycle arrest in the G2/M phase and produced caspase-induced apoptosis of HT29 cells through mitochondrial dysfunction. Also, 12a and 12d inhibited HDAC8, 6, and 11 activities. Furthermore, lead compound 12a exhibited higher metabolic stability than isoCA-4 and was highly potent in suppressing tumor growth in the fibrosarcoma MCA205 tumor model. Collectively, these studies suggest that 12a represents a new dual inhibitor of TP and HDAC activities, which makes it a suitable candidate for further investigations in clinical development.

Characterization of Microtubule Destabilizing Drugs: A Quantitative Cell-Based Assay That Bridges the Gap between Tubulin Based- and Cytotoxicity Assays.

(1) Background: Microtubule depolymerizing agents (MDAs) are commonly used for cancer treatment. However, the therapeutic use of such microtubule inhibitors is limited by their toxicity and the emergence of resistance. Thus, there is still a sustained effort to develop new MDAs. During the characterization of such agents, mainly through in vitro analyses using purified tubulin and cytotoxicity assays, quantitative comparisons are mandatory. The relationship between the effect of the drugs on purified tubulin and on cell viability are not always direct. (2) Methods: We have recently developed a cell-based assay that quantifies the cellular microtubule content. In this study, we have conducted a systematic comparative analysis of the effect of four well-characterized MDAs on the kinetics of in vitro tubulin assembly, on the cellular microtubule content (using our recently developed assay) and on cell viability. (3) Conclusions: These assays gave complementary results. Additionally, we found that the drugs' effect on in vitro tubulin polymerization is not completely predictive of their relative cytotoxicity. Their effect on the cellular microtubule content, however, is closely related to their effect on cell viability. In conclusion, the assay we have recently developed can bridge the gap between in vitro tubulin assays and cell viability assays.

Cyclic bridged analogs of isoCA-4: Design, synthesis and biological evaluation.

In this work, a series of cyclic bridged analogs of isocombretastatin A-4 (isoCA-4) with phenyl or pyridine linkers were designed and synthesized. The synthesis of the desired analogs was performed by the formation of nitro-vinyl intermediates, followed by a Cadogan cyclization. Structure activity relationship (SAR) study demonstrates the critical role of the combination of quinaldine as ring A, pyridine as the linker, and indole as ring B in the same molecule, for the cytotoxic activity. Among all tested compounds, compound 42 showed the highest antiproliferative activity against a panel of cancer cell lines with average IC50 values of 5.6 nM. Also, compound 42 showed high antiproliferative activity against the MDR1-overexpressing K562R cell line; thus, it was 1.5- and 12-fold more active than the reference compounds, isoCA-4 and CA-4, respectively. Moreover, 42 displayed a strong antiproliferative activity against the colon-carcinoma cells (HT-29), which are resistant to combretastatin A-4 and isoCA-4, and it was found to be 8000-fold more active than natural CA-4. Compound 42 also effectively inhibited tubulin polymerization both in vitro and in cells, and induced cell cycle arrest in G2/M phase. Next, we demonstrated that compound 42 dose-dependently caused caspase-induced apoptosis of K562 cells through mitochondrial dysfunction. Finally, we evaluated the effect of compound 42 in human no cancer cells compared to the reference compound. We demonstrated that 42 was 73 times less cytotoxic than isoCA-4 in quiescent peripheral blood lymphocytes (PBLs). In summary, these results suggest that compound 42 represents a promising tubulin inhibitor worthy of further investigation.