Defects in cell death signaling pathways are one of the hallmarks of cancer and can lead to resistance to conventional therapy. Natural products are promising compounds that can overcome this resistance. In the present study we studied the effect of six quaternary benzophenanthridine alkaloids (QBAs), sanguinarine, chelerythrine, sanguirubine, chelirubine, sanguilutine, and chelilutine, on Jurkat leukemia cells, WT, and cell death deficient lines derived from them, CASP3/7/6-/- and FADD-/-, and on solid tumor, human malignant melanoma, A375 cells. We demonstrated the ability of QBAs to overcome the resistance of these deficient cells and identified a novel mechanism for their action. Sanguinarine and sanguirubine completely and chelerythrine, sanguilutine, and chelilutine partially overcame the resistance of CASP3/7/6-/- and FADD-/- cells. By detection of cPARP, a marker of apoptosis, and pMLKL, a marker of necroptosis, we proved the ability of QBAs to induce both these cell deaths (bimodal cell death) with apoptosis preceding necroptosis. We identified the new mechanism of the cell death induction by QBAs, the downregulation of the apoptosis inhibitors cIAP1 and cIAP2, i.e., an effect similar to that of Smac mimetics.

• Keywords
• Smac mimetic drug resistance, apoptosis, benzophenanthridine alkaloids, cIAP, cancer, cell death, chelerythrine, sanguinarine,
• MeSH
• Alkaloids * pharmacology   metabolism   MeSH
• Apoptosis * MeSH
• Benzophenanthridines pharmacology   MeSH
• Caspase 3 metabolism   MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Signal Transduction MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Alkaloids * MeSH
• Benzophenanthridines MeSH
• Caspase 3 MeSH

Aberrant expression of proteins involved in cell division is a constant feature in multiple myeloma (MM), especially in high-risk disease. Increasingly, therapy of myeloma is moving towards individualization based on underlying genetic abnormalities. Aurora kinases are important mediators of cell cycle and are up regulated in MM. Functional loss of Aurora kinases results in genetic instability and dysregulated division leading to cellular aneuploidy and growth arrest. We investigated the role of Aurora kinase inhibition in MM, using a small molecule inhibitor A1014907. Low nanomolar A1014907 concentrations induced aneuploidy in MM cell lines independent of underlying cytogenetic abnormalities by inhibiting Aurora Kinases. However, A1014907 induced more pronounced and dose dependent apoptosis in cell lines with t(4;14) translocation. Translocation t(4;14) is observed in about 15% of patients with MM leading to constitutive activation of FGFR3 in two-thirds of these patients. Further investigation of the mechanism of action of A1014907 revealed potent FGFR3 pathway inhibition only in the sensitive cell lines. Thus, our results show that aurora kinase inhibition causes cell cycle arrest and aneuploidy with minimal apoptosis whereas inhibiting both aurora kinase and FGFR3 activity induced potent apoptosis in MM cells. These results support clinical evaluation of A1014907 in MM patients with t(4;14) translocation and/or FGFR3 expression.

• Keywords
• Aurora kinase, FGFR3, apoptosis, multiple myeloma, proliferation,
• Publication type
• Journal Article MeSH

Bcl2 and IAP families are anti-apoptotic proteins deregulated in multiple myeloma (MM) cells. Pharmacological inhibition of each of these families has shown significant activity only in subgroups of MM patients. Here, we have examined a broad-spectrum Bcl2 family inhibitor Obatoclax (OBX) in combination with a Smac mimetic LCL161 in MM cell lines and patient cells. LCL161/OBX combination induced synergistic cytotoxicity and anti-proliferative effects on a broad range of human MM cell lines. The cytotoxicity was mediated through inhibition of the IAPs, activation of caspases and up regulation of the pro-apoptotic proteins Bid, Bim, Puma and Noxa by the drug combination. In addition, we observed that OBX caused ER stress and activated the Unfolded Protein Response (UPR) leading to drug resistance. LCL161, however inhibited spliced Xbp-1, a pro-survival factor. In addition, we observed that OBX increased GRP78 localization to the cell surface, which then induced PI3K dependent Akt activation and resistance to cell death. LCL161 was able to block OBX induced Akt activation contributing to synergistic cell death. Our results support clinical evaluation of this combination strategy in relapsed refractory MM patients.

• Keywords
• Bcl-2, GRP78, IAP, apoptosis, myeloma,
• MeSH
• Apoptosis drug effects   MeSH
• Endoplasmic Reticulum Chaperone BiP MeSH
• Drug Resistance, Neoplasm MeSH
• Down-Regulation MeSH
• Phosphatidylinositol 3-Kinases metabolism   MeSH
• Phosphorylation MeSH
• Indoles MeSH
• Intracellular Signaling Peptides and Proteins agonists   MeSH
• Caspases metabolism   MeSH
• Humans MeSH
• Neoplasm Recurrence, Local drug therapy   pathology   MeSH
• Mitochondrial Proteins agonists   MeSH
• Multiple Myeloma drug therapy   pathology   MeSH
• Cell Line, Tumor MeSH
• Apoptosis Regulatory Proteins MeSH
• Heat-Shock Proteins metabolism   MeSH
• Antineoplastic Agents pharmacology   therapeutic use   MeSH
• Antineoplastic Combined Chemotherapy Protocols pharmacology   therapeutic use   MeSH
• Proto-Oncogene Proteins c-akt metabolism   MeSH
• Proto-Oncogene Proteins c-bcl-2 antagonists & inhibitors   metabolism   MeSH
• Pyrroles pharmacology   therapeutic use   MeSH
• Unfolded Protein Response drug effects   MeSH
• Endoplasmic Reticulum Stress drug effects   MeSH
• Drug Synergism MeSH
• Thiazoles pharmacology   therapeutic use   MeSH
• Up-Regulation MeSH
• X-Box Binding Protein 1 metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• BCL2 protein, human MeSH Browser
• Endoplasmic Reticulum Chaperone BiP MeSH
• DIABLO protein, human MeSH Browser
• HSPA5 protein, human MeSH Browser
• Indoles MeSH
• Intracellular Signaling Peptides and Proteins MeSH
• Caspases MeSH
• LCL161 MeSH Browser
• Mitochondrial Proteins MeSH
• obatoclax MeSH Browser
• Apoptosis Regulatory Proteins MeSH
• Heat-Shock Proteins MeSH
• Antineoplastic Agents MeSH
• Proto-Oncogene Proteins c-akt MeSH
• Proto-Oncogene Proteins c-bcl-2 MeSH
• Pyrroles MeSH
• Thiazoles MeSH
• XBP1 protein, human MeSH Browser
• X-Box Binding Protein 1 MeSH