coibamide-a and Breast-Neoplasms

Natural products are useful tools for biological mechanism research and drug discovery. Due to the excellent tumor cell growth inhibitory profile and sub-nanomolar potency, Coibamide A (CA), an N-methyl-stabilized depsipeptide isolated from marine cyanobacterium, has been considered as a promising lead compound for cancer treatment. However, the molecular anti-cancer mechanism of the action of CA remains unclear. Here, we showed that CA treatment induced caspase-independent cell death in breast cancer cells. CA treatment also led to severe lysosome defects, which was ascribed to the impaired glycosylation of lysosome membrane protein LAMP1 and LAMP2. As a consequence, the autophagosome-lysosome fusion was blocked upon CA treatment. In addition, we presented evidence that this autophagy defect partially contributed to the CA treatment-induced tumor cell death. Together, our work uncovers a novel mechanism underlying the anti-cancer action of CA, which will promote its further application for cancer therapy.

Topics: Antineoplastic Agents; Autophagosomes; Autophagy; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Depsipeptides; Female; Humans; Lysosomes; Signal Transduction

To enable the large-scale synthesis of coibamide A, we developed an improved synthetic strategy for this class of cyclodepsipeptide. The versatility of the synthetic procedure was demonstrated by the preparation of a series of designed coibamide A analogues, which enabled the preliminary structure-activity relationship (SAR) studies for this compound. Although most modifications of coibamide A resulted in decrease or loss of the antiproliferativity, we found that versatile substitution at position 3 was well tolerated. Remarkably, a simplified analogue, [MeAla3-MeAla6]-coibamide (1f), not only showed nearly the same inhibition as coibamide A against the tested cancer cells but also significantly inhibited tumor growth in vivo. The improved synthetic strategy and the relevant trends of SAR disclosed in this study will be valuable for further optimization of the overall profile of coibamide A.

Topics: Animals; Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Proliferation; Depsipeptides; Female; Humans; Mice; Mice, Nude; Molecular Structure; Structure-Activity Relationship; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

Coibamide A is a cytotoxic lariat depsipeptide isolated from a rare cyanobacterium found within the marine reserve of Coiba National Park, Panama. Earlier testing of coibamide A in the National Cancer Institute in vitro 60 human tumor cell line panel (NCI-60) revealed potent anti-proliferative activity and a unique selectivity profile, potentially reflecting a new target or mechanism of action. In the present study we evaluated the antitumor activity of coibamide A in several functional cell-based assays and in vivo. U87-MG and SF-295 glioblastoma cells showed reduced migratory and invasive capacity and underwent G1 cell cycle arrest as, likely indirect, consequences of treatment. Coibamide A inhibited extracellular VEGFA secreted from U87-MG glioblastoma and MDA-MB-231 breast cancer cells with low nM potency, attenuated proliferation and migration of normal human umbilical vein endothelial cells (HUVECs) and selectively decreased expression of vascular endothelial growth factor receptor 2 (VEGFR2). We report that coibamide A retains potent antitumor properties in a nude mouse xenograft model of glioblastoma; established subcutaneous U87-MG tumors failed to grow for up to 28 days in response to 0.3 mg/Kg doses of coibamide A. However, the natural product was also associated with varied patterns of weight loss and thus targeted delivery and/or medicinal chemistry approaches will almost certainly be required to improve the toxicity profile of this unusual macrocycle. Finally, similarities between coibamide A- and apratoxin A-induced changes in cell morphology, decreases in VEGFR2 expression and macroautophagy signaling in HUVECs raise the possibility that both cyanobacterial natural products share a common mechanism of action.

Topics: Animals; Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Cell Proliferation; Depsipeptides; Female; Glioblastoma; Human Umbilical Vein Endothelial Cells; Humans; Mice; Mice, Nude; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2; Xenograft Model Antitumor Assays