Expression of MICA, MICB and NKG2D in human leukemic myelomonocytic and cervical cancer cells

Abstract

BackgroundCancer cells are known to secrete the stress molecules MICA and MICB that activate cytotoxicity by lymphocytes and NK cells through their NKG2D receptor as a mechanism of immunological defense. This work was undertaken to evaluate if cancer cells can also express this receptor as a possible mechanisms of depletion of MIC molecules and thus interfere with their immune recognition.MethodsMyelomonocytic leukemic (TPH-1 and U-937) and cervical cancer (CALO and INBL) cell lines were evaluated by Western Blot, ELISA, flow cytometry and immunocytochemistry to evaluate their capacity to express and secrete MICA and MICB and to be induced to proliferate by these molecules as well as to express their receptor NKG2D. Statistical analysis was performed by two-way ANOVA for time course analysis and Student's t-test for comparison between groups. Values were considered significantly different if p < 0.05.ResultsTHP-1 and U-937 produce and secrete the stress MICA and MICB as shown by Western Blot of lysed cells and by ELISA of their conditioned media. By Western Blot and flow cytometry we found that these cells also express the receptor NKG2D. When THP-1 and U-937 were cultured with recombinant MICA and MICB they exhibited a dose dependent induction for their proliferation. CALO and INBL also produce MICA and MICB and were induced to proliferate by these stress molecules. By Western Blot, flow cytometry and immunocytochemistry we also found that these cells express NKG2D.ConclusionsOur novel results that tumor cells can simultaneously secrete MIC molecules and express their receptor, and to be induced for proliferation by these stress molecules, and that tumor epithelial cells can also express the NKG2D receptor that was thought to be exclusive of NK and cytotoxic lymphocytes is discussed as a possible mechanism of immunological escape and of tumor growth induction.

Hematological Malignancies Escape from NK Cell Innate Immune Surveillance: Mechanisms and Therapeutic Implications

“…Moreover, MICA and MICB appeared to act as a tumor-growth factor resulting in strong tumor proliferation in dose-dependent induction [26]. …”

Overexpression of brachyury contributes to tumor metastasis by inducing epithelial-mesenchymal transition in hepatocellular carcinoma

“…Western blot analysis was performed as described previously [24]. In brief, the membranes with total protein were incubated with primary antibodies: anti-Brachyury and anti-Snail (1:1000 dilutions; Cell Signaling Technology, Danvers, USA), anti-E-cadherin, anti-γ-catenin, antivimentin, anti-Akt, anti-p-Akt, and anti-PTEN (1:200 dilution; Santa Cruz Biotechnology, Santa Cruz, USA).…”

Sulforaphane induces ROS mediated induction of NKG2D ligands in human cancer cell lines and enhances susceptibility to NK cell mediated lysis

“…U-937 monocytic cell lines have high surface expression as well as secrete MICA and MICB. Interestingly, these cells also express NKG2D, the receptor for the secreted proteins and MICA and MICB secreted by the tumor cells can be recognized by their own NKG2D receptor to contribute to tumor cell proliferation [37].…”