Neutrophil assists the pro-apoptotic activity of SLPI (Secretory leukocyte protease inhibitor) on mammary tumor cell lines

AMIANO, NICOLÁS; TATEOSIAN, NANCY; PAYÉS, CRISTIAN; ALIJA, ANA; SANCHEZ, MERCEDES; CHULUYAN, EDUARDO

Buenos Aires

Congreso; First French-Argentine Immunology Congress; 2010

SAI

SLPI is an 11.7 kDa protein that plays an important role in protectionagainst neutrophil proteases during the inflammatoryresponse. In previous results we demonstrated that SLPI inducesapoptosis of mammary tumor cells. Moreover, we described thatmice mammary tumor cells SLPI overexpressing (2C1), do notdevelop tumors in Balb/c mice but grow in mice-depleted neutrophils(PMN). The aim of the present work was to examine thecontribution of PMN to the pro-apoptotic activity of the SLPI.Apoptosis was evaluated by flow cytometry. Balb/c mice wereinoculated or not with 2C1 cells (SLPI over-expressing cells derivedfrom F3II cells). Plasma from those animals were obtainedat day 2 and 7 post-inoculation and it assessed for apoptosisactivity on 2C1 cells in vitro. Plasma from 2C1 inoculated animalsbut not control plasma, induced in vitro apoptosis of 2C1 cells(48h: Control: 37±4%; 2C1 plasma: 55±6%; p<0.05; 7d: Control:53±10%; 2C1 plasma: 83±12%; p<0.05). The apoptotic activity ofplasma from 2C1-inoculated mice, was partially lost if animalswere previously PMN depleted (Control plasma: 53±12%; PMNdepleted plasma: 14±4%, p<0.01). These results confirmed thatthe in vivo apoptotic effect of SLPI is, in part, mediated throughPMN. Then, we set up an in vitro model to test if we can resemblethe in vivo situation. For this, human mammary tumorcell line (MDA-MB231), HeLa (cervix carcinoma) and A549 (lungcarcinoma) were treated with exogenous rhSLPI in the presenceof neutrophils. We observed that PMN increased the apoptosisof the MDA-MB231 induced by SLPI (SLPI: 25±1%; SLPI + PMN:30±1%, p<0.05). On the contrary, apoptosis of HeLa and A549cells were significantly decreased when they were treated withSLPI + PMN (HeLa: SLPI: 55±5% vs SLPI + PMN: 42±1%, p<0.05;A549: SLPI: 53±1% vs SLPI+PMN: 44±1%, p<0.05). Overall, theseresults suggest that the neutrophils help the pro-apoptotic activityof SLPI on mammary tumor cells but not on HeLa or A549cell lines.