Enhanced anti-colorectal cancer effects of carfilzomib combined with CPT-11 via downregulation of nuclear factor-κB in vitro and in vivo

Jun 28, 2014International journal of oncology

Stronger anti-colorectal cancer effects of carfilzomib combined with CPT-11 linked to reduced NF-κB activity in lab and animal studies

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Abstract

Carfilzomib (CFZ) significantly inhibited the growth of SW620 colorectal cancer cells and enhanced the effects of irinotecan (CPT-11).

CFZ alone or in combination with CPT-11 reduced cell survival and colony formation in colorectal cancer cells.
The combination treatment may inhibit NF-κB activation and alter key signaling pathways, including MEK/ERK and PI3K/AKT.
Co-administration of CFZ and CPT-11 resulted in G2/M cell cycle arrest and increased expression of p21WAF1/CIP.
Increased apoptosis was observed with higher levels of PARP cleavage and caspase 3 activation after combination treatment.
The combined treatment reduced the invasive and migratory capabilities of colorectal cancer cells by altering protein expression of MMP and TIMP.
In vivo studies showed that CFZ and CPT-11 together suppressed tumor growth more effectively than either agent alone.

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Upregulation of nuclear factor-κB (NF-κB) in colorectal carcinoma (CRC) accelerates tumor growth, whereas, irinotecan (CPT-11)-induced NF-κB activation reduces chemosensitivity and weakens the anti-colorectal cancer function itself, while proteasome inhibitors can inhibit NF-κB and improve the effect of chemotherapy. Carfilzomib (CFZ) is a novel proteasome inhibitor that has been recently approved by the FDA and is in clinical use for the treatment of multiple myeloma, but little is known about its activity against CRC. The aim of the present study was to explore whether CFZ alone or in combination with CPT-11 is effective in CRC treatment. We evaluated the novel therapeutic ability and mechanism of action of CFZ in CRC in vitro and in vivo. SW620 cells were incubated with CFZ alone or in combination with CPT-11. Cell proliferation was assessed by WST-1 and clonogenic assays, the cytotoxic interaction was assessed with a combination index (CI). Cell cycle progression was analysed with flow cytometry. Cell apoptosis was evaluated by detecting the Annexin V/propidium iodide (PI) ratio, caspase 3 and CD95 expression, and with TUNEL staining. Cell migration and invasion was determined with a wound-healing assay and a Transwell matrix penetration assay. A CRC xenograft model was established to monitor tumor growth. EMSA was used to analyse NF-κB activation and western blot analysis was used to detect the protein levels of related signaling factors. CFZ significantly inhibited the growth of SW620 cells, and had synergistic inhibitory effects with CPT-11 on survival and colony formation; possibly by inhibition of NF-κB activation, MEK/ERK and PI3K/AKT pathway factor dephosphorylation and survivin downregulation. Co-administration of CFZ and CPT-11 induced G2/M arrest, increased p21WAF1/CIP, and decreased mutant p53 and cdc25c expression. Induction of apoptosis was accompanied by marked increases in PARP cleavage, caspase 3 activation, an increase of CD95 and p-p38, and ATF3 activation. Combination treatment lowered the invasive and migration ability of SW620 cells, reduced MMP and increased TIMP protein expression. Finally, co-administration of CFZ and CPT-11 suppressed tumor growth and increased apoptosis compared with single-agent treatment in SW620 xenograft models correlated with NF-κB downregulation. Carfilzomib alone or in combination with CPT-11 is effective against colorectal cancer through inhibition of multiple mechanisms related to NF-κB, and could be a potential novel therapy for CRC.

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Abstract

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