The type 2 transmembrane serine protease matriptase is under tight control primarily by the actions of the integral membrane Kunitz-type serine protease inhibitor HAI-1. Growing evidence indicates that HAI-2 might also be involved in matriptase inhibition in some contexts. Here we showed that matriptase inhibition by HAI-2 depends on the subcellular localizations of HAI-2, and is observed in breast cancer cells but not in mammary epithelial cells. HAI-2 is co-expressed with matriptase in 21 out of 26 human epithelial and carcinoma cells examined. HAI-2 is also a potent matriptase inhibitor in solution, but in spite of this, HAI-2 inhibition of matriptase is not observed in all contexts where HAI-2 is expressed, unlike what is seen for HAI-1. Induction of matriptase zymogen activation in mammary epithelial cells results in the formation of matriptase-HAI-1 complexes, but matriptase-HAI-2 complexes are not observed. In breast cancer cells, however, in addition to the appearance of matriptase-HAI-1 complex, three different matriptase-HAI-2 complexes, are formed following the induction of matriptase activation. Immunofluorescent staining reveals that activated matriptase is focused at the cell-cell junctions upon the induction of matriptase zymogen activation in both mammary epithelial cells and breast cancer cells. HAI-2, in contrast, remains localized in vesicle/granule-like structures during matriptase zymogen activation in human mammary epithelial cells. In breast cancer cells, however, a proportion of the HAI-2 reaches the cell surface where it can gain access to and inhibit active matriptase. Collectively, these data suggest that matriptase inhibition by HAI-2 requires the translocation of HAI-2 to the cell surface, a process which is observed in some breast cancer cells but not in mammary epithelial cells.
Colorectal cancer is the third leading cause of cancer-related death in the United States. About 15% of colorectal cancers are associated with microsatellite instability (MSI) due to loss of function in the DNA mismatch repair pathway. This subgroup of patients has better survival rates and is more sensitive to immunotherapy. However, it remains unclear whether microsatellite stable (MSS) patients with colorectal cancer can be further stratified into subgroups with differential clinical characteristics. In this study, we analyzed The Cancer Genome Atlas data and found that Chr20q amplification is the most frequent copy number alteration that occurs specifically in colon (46%) and rectum (61%) cancer and is mutually exclusive with MSI. Importantly, MSS patients with Chr20q amplification (MSS-A) were associated with better recurrence-free survival compared with MSS patients without Chr20q amplification (MSS-N; P = 0.03). MSS-A tumors were associated with high level of chromosome instability and low immune infiltrations. In addition, MSS-A and MSS-N tumors were associated with somatic mutations in different driver genes, with high frequencies of mutated TP53 in MSS-A and mutated KRAS and BRAF in MSS-N. Our results suggest that MSS-A and MSS-N represent two subtypes of MSS colorectal cancer, and such stratification may be used to improve therapeutic treatment in an individualized manner.
Significance:
This study shows that chromosome 20q amplification occurs predominately in microsatellite-stable colorectal cancer and defines a distinct subtype with good prognosis, high chromosomal instability, distinct mutation profiles, and low immune infiltrations.
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