The STAT3 pathway is important to the development of many cancers, but so far, no Food and Drug Administration–approved drugs are ready for clinical use. Napabucasin, a novel oral small-molecule inhibitor of signal transducer and activator of transcription 3 (STAT3), blocks tumor growth and resists metastasis in a broad spectrum of solid tumors. Napabucasin was now found to be effective in inhibiting diffuse large beta cell lymphoma (DLBCL) in cell lines and in in vitro testing, as reported by Xue Li of the West China Hospital, Sichuan (China) University, and colleagues.
In addition, the effects of napabucasin were found to be synergistic with the use of doxorubicin, a standard DLBCL therapy agent, according to the report, published online in Cancer Letters.
‘Dramatic’ results
The researchers found that 34% (23/69) of DLBCL patients expressed STAT3 in tumor tissues. When they tested napabucasin in a variety of DLBCL cell lines they found that the drug exhibited potent cytotoxicity in a dose-dependent manner. In addition, they found that napabucasin induced intrinsic and extrinsic cell apoptosis, downregulated the expression of STAT3 target genes, including the antiapoptotic protein Mcl-1, and regulated the mitogen-activated protein kinase (MAPK) pathway, all important indicators of antitumor effectiveness in vitro.
In cells treated with napabucasin and doxorubicin alone and in combination, napabucasin alone significantly suppressed tumor growth, compared with that of the control (P < .01), achieving tumor growth inhibition (TGI) of 78.8%. The combination treatment, “with a dramatic TGI of 98.2%,” was more effective than doxorubicin monotherapy (TGI = 63.2%; P < .05), according to the researchers.
“Our study provided evidence that napabucasin is an attractive candidate drug either as a monotherapy or in combination therapies for DLBCL treatment. Further work studying the clinical efficacy and combination treatment schedule should be performed for personalized therapy,” the researchers concluded.
The work was supported by grants from the Chinese government. The authors stated that they had no conflicts of interest.
SOURCE: Li X et al. Cancer Lett. 2020 Aug 14. doi: 10.1016/j.canlet.2020.07.032.