Hypoxia stimulates breast carcinoma cell invasion through MT1-MMP and MMP-2 activation.

The process of cancer cell invasion involves degradation of the extracellular matrix (ECM) by proteases, integrin adhesion and cell motility. The role of ECM degrading proteases on the hypoxia-induced invasion of breast carcinoma cells was investigated. Hypoxia markedly increased the invasion capacity of MDA-MB-231 and MDA-MB-435 breast carcinoma cell lines. Matrix metalloproteinase (MMP) inhibitors blocked the hypoxia-induced invasion, whereas other protease inhibitors had no effect. Antibodies or siRNAs blocking either membrane type-1 MMP (MT1-MMP) or MMP-2 were effective in reducing the hypoxia-induced invasion. Serum-free reconstitution experiments confirmed the involvement of the MT1-MMP/MMP-2/tissue inhibitor of metalloproteinase-2 complex in this hypoxia-induced response. Overexpression of MT1-MMP in a poorly invasive breast cancer cell line, T47-D, promoted hypoxia-induced invasion and MMP-2 activation. Cell surface accumulation and activation of MT1-MMP without apparent regulation at the mRNA or protein levels indicated a post-translational adaptive response to hypoxia. Inhibition of the small GTPase RhoA eliminated the hypoxia-induced invasion and blocked the localization of MT1-MMP to the plasma membrane. Zymographic and molecular analysis of human breast tumors showed a strong correlation between hypoxic microenvironments and MMP-2 activation without changes in MT1-MMP expression. Our studies suggest that hypoxic tumor microenvironments promote breast cancer invasion through an MT1-MMP-dependent mechanism.

An operon that confers UV resistance by evoking the SOS mutagenic response in streptococcal conjugative transposon Tn5252.

Streptococcus pneumoniae Rx1 is capable of repairing lesions caused by DNA-damaging agents in an error-free manner but lacks a UV-inducible error-prone repair system due to the absence of chromosomally encoded UmuDC-like proteins. We have identified an operon-like structure 8 kb from the left end of the pneumococcal conjugative transposon Tn5252 that confers SOS function in the host cells. DNA sequence analysis of this region revealed the presence of four open reading frames (ORFs). The deduced amino acid sequence of one of them, ORF13, which is capable of encoding a protein of 49.7 kDa, showed significant homology to UmuC, MucB, and other proteins involved in the SOS response. The carboxy-terminal region of another, ORF14, which is predicted to encode a 26-kDa polypeptide, shared similarity with UmuD- and MucA-like proteins that carry the amino acid residues recognized by the activated RecA* protein for proteolytic cleavage. The presence of plasmids carrying subcloned DNA from this region was found to restore UV-inducible mutagenic repair of chromosomal DNA in Escherichia coli cells defective in error-prone repair as well as in pneumococcus and Enterococcus faecalis UV202. Mutations within ORF13 abolished UV-induced mutagenesis but did not affect the conjugal transposition of the element.

Recombinant antigens for specific and sensitive serodiagnosis of Latin American tegumentary leishmaniasis.

The diagnostic potential of recombinant leishmanial antigens for Latin American tegumentary leishmaniasis (LATL) was examined. Two Leishmania (Viannia) peruviana recombinant proteins, T26-U2 and T26-U4, were assessed by their reactivity to detect specific anti-leishmanial antibodies. Seventy-eight individual sera from persons with LATL, 39 from those with other diseases, and 10 negative control sera were tested by Western blotting and enzyme-linked immunosorbent assay. The sensitivity of the test using T26-U2 plus T26-U4 was similar to that obtained with whole parasite extract (92%). However, the specificity obtained using both recombinant antigens (87%) was higher than that of the whole parasite extract (65%). All tests using recombinant proteins (T26-U2, T26-U2 plus T26-U4 or T26-U4) had a higher positive predictive value (89%, 92% and 98%, respectively) than the value obtained using total parasites (81%). Eleven Colombian sera were also tested, and the results indicated that T26-U2 plus T26-U4 could be used successfully in Peru and in other Latin American countries.