Calpain‐2 inhibitor treatment preferentially reduces tumor progression for human colon cancer cells expressing highest levels of this enzyme

Abstract

Calpain‐2 levels are higher in colorectal tumors resistant to chemotherapy and previous work showed calpain‐2 inhibitor therapy reduced inflammation‐driven colorectal cancer, but direct effects of the inhibitor on colon cancer cells themselves were not demonstrated. In the present study, five human colon cancer cell lines were directly treated with a calpain‐2 inhibitor and results showed increased cell death in 4 of 5 cell lines and decreased anchorage‐independent growth for all cell five lines. When tested for levels of calpain‐2, three cell lines exhibited increasing levels of this enzyme: HCT15 (low), HCC2998 (medium), and HCT116 (significantly higher). This was consistent with gel shift assays showing that calpain‐2 inhibitor reduced of NF‐κB nuclear translocation most effectively in HCT116 cells. Ability of calpain‐2 inhibitor to impede tumor progression in vivo was evaluated using intrarectal transplant of luciferase‐expressing cells for these three cell lines. Results showed that calpain‐2 inhibitor therapy reduced tumor growth and increased survival only in mice injected with HCT116 cells. These data suggest calpain‐2 inhibitor treatment may be most effective on colorectal tumors expressing highest levels of calpain‐2.

Calpain-2 participates in the process of calpain-1 inactivation

“…For this purpose, we compared the expression levels of CAPN1, CAPN2, CAPNS1 and CAST in different cell lines and chose human HCT116 colon cancer cells (Supplementary Figure S3A). HCT116 have increased levels of CAPN2 in comparison with other colon cancer cell lines [ 38 ], and we also confirmed that protein levels of CAPN1 and CAPN2 are significantly higher than those in HeLa or HEK293 cells while the amount of CAST is moderate (Supplementary Figure S3B). Difference of calpain enzymatic activities in these cell lines was discernible as proteolysis of spectrin and autolysis of CAPN1 (Supplementary Figure S3C,D).…”

“…As an indication of physiological significance of reciprocal regulation between C1 and C2, we focused on that relative expression levels of CAPN1, CAPN2, CAPNS1 and CAST vary among cell lines. For example, altered expression levels of CAPN1 or CAPN2 have been related to pathogenic phenotypes such as malignancy potency [ 38 , 45 ]. In these cases, however, the phenomenon is often explored to identify which calpain, C1 or C2, is the preferential isoform involved in the proteolysis of defined substrates.…”

Blocking the Cleavage of Filamin A by Calpain Inhibitor Decreases Tumor Cell Growth

“…For these reasons, calpains are considered by several studies as potential anti-cancer targets. The beneficial effect of blocking the calpain system has been reported in multiple human cancer cells, including breast (18), colon (19), pleural mesothelioma (20), pancreas (21), and prostate ( 22) cancers. In addition, several human cancers display aberrant expression of calpains (23).…”

“…Production of FLNA CT was inhibited after treatment with calpeptin. Immunoblots of full-length FLNA, FLNACT (16)(17)(18)(19)(20)(21)(22)(23)(24), and actin in A7, PC3, T241, and MS1 cells treated with calpeptin (100 μM) or with DMSO alone (left panels). Quantification of densitometric readings of the immunoblot bands is shown in the right graph.…”

Calpain–calpastatin system and cancer progression

“…The apoptosis-caspase system can be activated after calpain inhibition with calpain inhibitor II in neoplastic lymphoid cells (Zhu & Uckun, 2000). Increased levels of m-calpain have been found in human chemotherapy-resistant colorectal adenocarcinoma, together with decreased expression of the calpain inhibitors calpastatin and high molecular weight calmodulinbinding protein (HMWCaMBP) (Lakshmikuttyamma et al, 2004), suggesting that m-calpain inhibitor treatment may be more effective in this type of colorectal tumour (Lakshmikuttyamma et al, 2004;Marciel et al, 2018).…”