(Original magnification × 40) Figure 6 Cervical cancer cell lines secrete MICA and MICB. Cells (5 × 103) were cultured in 48-well plates for 7 days, the supernatants were collected every 24 h, and MICA and MICB proteins were detected by ELISA using specific monoclonal antibodies. Data

from CALO (A) and INBL (B) cells are shown. CALO and INBL proliferate in response to MICA and MICB After we detected the expression p38 MAPK inhibitors clinical trials of MICA, MICB, and NKG2D in CALO and INBL cells, we proceeded to evaluate if MICA and MICB could modulate their proliferation. For this purpose, we cultured 5 × 103 CALO and INBL cells for 3 days in the presence of 1, 10, or 100 ng of MICA or MICB and found that both ligands stimulated significant cell proliferation (Figure 7). Figure 7 MICA and MICB induce cervical cancer cell line proliferation. Cells (5 × 103) were cultured for

72 h in 96-well plates in the presence of 1, 10 or 100 ng recombinant human MICA or MICB. CALO (A) and INBL (B) cell proliferation was then assayed using the MTT technique. * indicates p < 0.05 Discussion The production of MICA and MICB by virus-infection or tumor cells has been previously reported [19, 20], and the ability of these ligands to induce cytotoxic activity in NK cells and other cytotoxic lymphocytes through the interaction with their cognate receptor, NKG2D, has been well established [21, 22]. Thus, a mechanism by which malignant cells express stress signals, O-methylated flavonoid and how other cells recognize those signals to become specifically cytotoxic and mount an immunological response to eradicate the tumor cells, has been clearly established. In this work, we present evidence Selleckchem GDC-0994 that both the stress signals and their cognate

receptor can be expressed on the same tumor cells. We showed that the leukemic U-937 and TPH-1 myelomonocytic cell lines secrete MICA and MICB, and that those cells also express NKG2D, the receptor for the secreted proteins. We found that ectopic MICA and MICB could induce a strong proliferative response on those cells, suggesting the possibility of an autoregulatory mechanism by which MICA and MICB secreted by the tumor cells are recognized by their own NKG2D receptor to contribute to tumor cell proliferation. The fact that these cells could express and secrete MICA and MICB was expected, because malignant cells are known to express these signal proteins; nevertheless, we were surprised that the same cells expressed NKG2D. We were further surprised when we found that epithelial human cervical cancer cell lines not only expressed MICA and MICB but also their receptor. We do not know why the levels of MICA and MICB took a longer time to be expressed in cervical cells than in myelomonocytic cells but we could speculate that it could be BX-795 mouse related to their doubling times in vitro because the cervical cells had a doubling time of more than 4 days, while the myelomonocytic ones of less than 3 days.