Effects of the Medicago scutellata trypsin inhibitor (MsTI) on cisplatin-induced cytotoxicity in human breast and cervical cancer cells.

BACKGROUND: Snail medic (Medicago scutellata L.) seeds exhibit a significantly higher content of a trypsin inhibitor than other Medicago species. This inhibitor belongs to the Bowman-Birk family of serine protease inhibitors (BBI) and exhibits a good sequence homology with the BBI from soybean, while presenting some differences. It has been suggested that BBIs have antitumoral and radio-protective activity. MATERIALS AND METHODS: In order to assess whether the inhibitor from Medicago scutellata (MsTI) seeds show similar properties to those of BBI from soybean with respect to potentiation of cisplatin-induced cytotoxicity, we evaluated the effects of MsTI on cisplatin-induced cell killing in MCF7 human breast carcinoma cells and HeLa human cervical carcinoma cells. RESULTS: The 24-hour treatment of MsTI in the cell culture medium decreased the clonogenic survival of MCF7 and HeLa cells in a dose-dependent manner and enhanced cisplatin-induced cytotoxicity. The presence of MsTI during the entire incubation period reduced the D37 of cisplatin by 40% in both the cell lines. CONCLUSION: MsTI could be an useful agent for the potentiation of cisplatin-mediated cancer treatment.

Dominant TCR-alpha requirements for a self antigen recognition in humans.

TCR-alpha and -beta chains are composed of somatically rearranged V, D, and J germline-encoded gene segments that confer Ag specificity. Recent crystallographic analyses revealed that TCR-alpha has more contacts with peptide than TCR-beta, suggesting the possibility that peptide recognition predominantly relies on TCR-alpha. T cells specific for the self Ag Melan-A/MART-1 possess an exceptionally high precursor frequency in human histocompatibility leukocyte Ag-A2 individuals. This provided a unique situation for assessment of the structural relationship between TCR and peptide/MHC ligand at both the pre- and postimmune levels. Molecular and phenotypic analysis of many different Melan-A-specific T cell populations revealed that a structural constraint is imposed on the TCR for engagement with Melan-A peptides presented by HLA-A2, namely the highly preferential use of a particular TCRAV segment, AV2. Examination of CD8 single-positive thymocytes indicated that this preferential use in forming the Melan-A-specific TCR is mainly imposed by intrathymic positive selection. Our data demonstrate a dominant function of TCRAV2 segment in forming the TCR repertoire specific for the human self Ag Melan-A/MART-1 and support the view that Ag recognition is mediated predominantly by TCR-alpha.

T-cell dynamics after high-dose chemotherapy in adults: elucidation of the elusive CD8+ subset reveals multiple homeostatic T-cell compartments with distinct implications for immune competence.

Recovery of total T cell numbers after in vivo T-cell depletion in humans is accompanied by complex perturbation within the CD8+ subset. We aimed to elucidate the reconstitution of CD8+ T cells by separate analysis of putative naïve CD95- CD28+, memory CD95+ CD28+ and CD28- T cell compartments after acute maximal depletion by high-dose chemotherapy (HD-ChT) in women with high-risk breast cancer. We found that recovery of putative naïve CD8+ CD95- CD28+ and CD4+ CD95- CD28+ T cells, was compatible with a thymus-dependent regenerative pathway since their recovery was slow and time-dependent, their values were tightly related to each other, and their reconstitution patterns were inversely related to age. By analysing non-naïve T cells, a striking diversion between putative memory T cells and CD28- T cells was found. These latter increased early well beyond normal values, thus playing a pivotal role in total T-cell homeostasis, and contributed to reduce the CD4 : CD8 ratio. In contrast, putative memory T cells returned to values not significantly different from those seen in patients at diagnosis, indicating that this compartment may recover after HD-ChT. At 3-5 years after treatment, naïve T cells persisted at low levels, with expansion of CD28- T cells, suggesting that such alterations may extend further. These findings indicate that CD28- T cells were responsible for 'blind' T-cell homeostasis, but support the notion that memory and naïve T cells are regulated separately. Given their distinct dynamics, quantitative evaluation of T-cell pools in patients undergoing chemotherapy should take into account separate analysis of naïve, memory and CD28- T cells.