Matrix metalloproteinase inhibitors: past lessons and future prospects in breast cancer

Blockade of MMP14 activity in murine breast carcinomas: implications for macrophages, vessels, and radiotherapy

BACKGROUND

Matrix metalloproteinase (MMP) 14 may mediate tumor progression through vascular and immune-modulatory effects.

METHODS

Orthotopic murine breast tumors (4T1 and E0771 with high and low MMP14 expression, respectively; n = 5-10 per group) were treated with an anti-MMP14 inhibitory antibody (DX-2400), IgG control, fractionated radiation therapy, or their combination. We assessed primary tumor growth, transforming growth factor β (TGFβ) and inducible nitric oxide synthase (iNOS) expression, macrophage phenotype, and vascular parameters. A linear mixed model with repeated observations, with Mann-Whitney or analysis of variance with Bonferroni post hoc adjustment, was used to determine statistical significance. All statistical tests were two-sided.

RESULTS

DX-2400 inhibited tumor growth compared with IgG control treatment, increased macrophage numbers, and shifted the macrophage phenotype towards antitumor M1-like. These effects were associated with a reduction in active TGFβ and SMAD2/3 signaling. DX-2400 also transiently increased iNOS expression and tumor perfusion, reduced tissue hypoxia (median % area: control, 20.2%, interquartile range (IQR) = 6.4%-38.9%; DX-2400: 1.2%, IQR = 0.2%-3.2%, P = .044), and synergistically enhanced radiation therapy (days to grow to 800mm(3): control, 12 days, IQR = 9-13 days; DX-2400 plus radiation, 29 days, IQR = 26-30 days, P < .001) in the 4T1 model. The selective iNOS inhibitor, 1400W, abolished the effects of DX-2400 on vessel perfusion and radiotherapy. On the other hand, DX-2400 was not capable of inducing iNOS expression or synergizing with radiation in E0771 tumors.

CONCLUSION

MMP14 blockade decreased immunosuppressive TGFβ, polarized macrophages to an antitumor phenotype, increased iNOS, and improved tumor perfusion, resulting in reduced primary tumor growth and enhanced response to radiation therapy, especially in high MMP14-expressing tumors.

Matrix metalloproteinases 2, 7, and 9 in tumors and sera of patients with breast cancer

Enzyme immunoassay showed that the content of matrix metalloproteinases (MMP) 2 and 7 in tumors was higher than in the adjacent histologically intact tissue in 91 and 76% patients with breast cancer, respectively, while MMP-9 levels in the tumor and intact tissue were virtually the same. Serum concentrations of MMP-2 and MMP-7 did not correlate with their levels in the tumors, were within the normal range, and virtually did not decrease after removal of the primary tumor. Serum levels of MMP-9 in patients were significantly lower than in the control and increased after surgery in 85% patients. No clear-cut relationship between the studied parameters and clinical morphological prognostic factors of breast cancer was detected.

Looking at the proteases from a simple perspective

Proteases have received enormous interest from the research and medical communities because of their significant roles in several human diseases. Some examples include the involvement of thrombin in thrombosis, HIV-1 protease in Acquired Immune Deficiency Syndrome, cruzain in Trypanosoma cruzi infection, and membrane-type 1 matrix metalloproteinase in tumor invasion and metastasis. Many efforts has been undertaken to design effective inhibitors featuring potent inhibitory activity, specificity, and metabolic stability to those proteases involved in such pathologies. Protease inhibitors usually target the active site, but some of them act by other inhibitory mechanisms. The understanding of the structure-function relationships of proteases and inhibitors has an impact on new inhibitor drugs designing. In this paper, the structures of four proteases (thrombin, HIV-protease, cruzain, and a matrix metalloproteinase) are briefly reviewed, and used as examples of the importance of proteases for the development of new treatment strategies, leading to a longer and healthier life.

Relationships between the level of matrix metalloproteinase-2 and tumor size of breast cancer

BACKGROUND

The involvements of matrix metalloproteinase-2 (MMP-2) in the pathogenesis of breast cancers have been established. We determined the concentrations of MMP-2 in serum samples and tumor tissues of breast cancer patients.

METHODS

Gelatin zymography and ELISA were used to measure MMP-2 and MMP-9 concentrations in 90 breast cancer patients, including 60 tissue samples and 30 serum samples.

RESULTS

ProMMP-2, activated MMP-2, proMMP-9 and activated MMP-9 levels were significantly higher in tumor tissues than that of corresponding paired adjacent normal tissue of 60 breast cancer patients (p<0.01). Further linear regression analysis has showed that the tumor size positively correlated with MMP-2 level in tumor tissue samples (R=0.55, p<0.0001), as well as with that of in serum samples (R=0.398, p=0.032). In addition, further statistical analysis for clinic pathological parameters revealed that MMP-2 level was significantly increased in patients with metastasis (p<0.05). Furthermore, MMP-2 level was significantly different between tumor grades (p=0.006).

CONCLUSIONS

MMP-2 levels in serum and tumor tissue might reflect the severity of invasion of breast cancer and various MMP inhibitors might be selectively used as potential anti-metastasis agents according to tumor size.