Cystatin M

Abstract

The contribution of pericellular proteolysis to tumor progression is well documented. To better understand protease biology and facilitate clinical translation, specific proteolytic systems need to be better defined. In particular, the precise role of endogenous protease inhibitors still needs to be deciphered. We reported previously that cystatin M, a potent endogenous inhibitor of lysosomal cysteine proteases, significantly suppressed in vitro cell proliferation, migration, and Matrigel invasion. Here, we show that scid mice orthotopically implanted with breast cancer cells expressing cystatin M show significantly delayed primary tumor growth and lower metastatic burden in the lungs and liver when compared with mice implanted with mock controls. The incidence of metastasis, however, appeared to be unaltered between the cystatin M group and the control group. Experimental metastasis assays suggest that cystatin M suppressed tumor cell proliferation at the secondary site. By using laser capture microdissection and quantitative reverse transcription-polymerase chain reaction, we found consistent expression of cystatin M in normal human breast epithelial cells, whereas expression was decreased by 86% in invasive ductal carcinoma (IDC) cells of stage I to IV patients. Complete loss of expression of cystatin M was observed in two of three IDCs from stage IV patients. Immunohistochemical studies confirmed that expression of cystatin M in IDCs was partially or completely lost. We propose cystatin M as a novel candidate tumor suppressor gene for breast cancer.

Cystatin E/M Suppresses Tumor Cell Growth through Cytoplasmic Retention of NF-κB

“…Our studies have also shown that the inactivation of the gene is associated with homozygous deletion, promoter hypermethylation, and somatic mutations in primary tumor samples (19). Cystatin E/M gene is expressed in ductal carcinoma in situ (DCIS) but not in metastatic breast cancer, pointing to inactivation during tumor progression (16)(17)(18)24). Finally, inactivation of cystatin E/M gene is associated with the loss of expression of estrogen and progesterone receptors and HER4, indicating an association with these proteins in the development of invasive breast cancers (25).…”

“…Numerous studies have shown inactivation of the cystatin E/M gene in human tumors (16)(17)(18)(19)(20)(21)(22)(23). However, all the functional studies relied on the exogenous expression of cystatin E/M using plasmid constructs.…”

“…A null mutation of the mouse cystatin E/M gene is also correlated with development of the ichq phenotype, characterized by neonatal lethality, abnormal cornification, and desquamation. Cystatin E/M was initially identified as a downregulated transcript in metastatic breast cancers (15,16). A number of studies have implicated cystatin E/M as a human tumor suppressor gene that is inactivated in the cancers of the breast, cervix, prostate, brain, and stomach (17)(18)(19)(20)(21)(22)(23).…”

Modelling family 2 cystatins and their interaction with papain

“…It directly regulates the activity of cathepsin V, cathepsin L and legumain, thereby controls the processing of transglutaminases (Cheng et al, 2006). Cystatin M/E is also reported as a novel candidate tumor suppressor gene for breast cancer (Zhang et al, 2004).…”

Identification of Cystatin SA as a Novel Inhibitor of Acid Ceramidase

“…Cystatin B also is elevated in tissues and the urine of bladder cancer patients, and its levels in urine are positively correlated with tumor grade, stage, and a shorter time to disease recurrence and progression (11). Decreased levels of cystatin C were found in the plasma of mice with Lewis lung adenocarcinoma (12), and cystatin E/M is a suppressor gene of cervical and breast cancer (13,14). One member of the salivary cystatins (cystatin SN) also was found to be differentially regulated (acti-vated or suppressed) in cancerous lesions of gastric cancer patient tissues (15).…”