Antitumor Effects In Vitro and In Vivo and Mechanisms of Protection against Melanoma B16F10-Nex2 Cells By Fastuosain, a Cysteine Proteinase from Bromelia fastuosa

Abstract

In the present work, the antitumor effect of fastuosain, a cysteine proteinase from Bromelia fastuosa, was investigated. In the intravenous model of lung colonization in C57BI/6 mice, fastuosain and bromelain injected intraperitoneally were protective, very few nodules of B16F10-Nex2 melanoma cells were detected. Tumor cells treated with fastuosain showed reduced expression of CD44 and decreased invasion through Matrigel, lost their cytoplasmic extensions and substrate adherence, became round and detached, forming strongly bound cell clusters in suspension. Peritoneal cells recruited and activated by fastuosain treatment (mainly monocytic cells and lymphocytes) migrated to the lung, where pulmonary melanoma metastases grew. Adoptive transference of peritoneal cells recruited by fastuosain had no protective effect against lung metastases in recipient mice. Treatment of green fluorescent protein -chimeric animals with fastuosain did not change the number of cells that migrated to the lung, compared to PBSinjected control mice, but the number of positive major histocompatibility complex class II cells increased with fastuosain treatment. Murine antibodies against fastuosain, bromelain, cathepsins B and L crossreacted in ELISA and recognized surface and cytoplasmic components expressed on B16F10-Nex2 cells. Anti-fastuosain antibodies were cytotoxic/lytic to B16F10-Nex2 cells. Antitumor effects of fastuosain involve mainly the direct effect of the enzyme and elicitation of protective antibodies.

Keywords

• Fastuosain
• bromelain
• B16F10-Nex2 tumor cells
• cathepsins B/L, protective antibodies