Resistance of ovarian teratocarcinoma cell spheroids to complement-mediated lysis

Abstract

Summary We have shown previously that it is possible to target complement-mediated killing against cultured ovarian tumour cells in vitro. As malignant ovarian cells usually grow in solid nodules in vivo, we have in the present study examined the effectiveness of complement killing against ovarian teratocarcinoma cells (PA-1) growing in three-dimensional tumour microspheroids (TMSs). Our study shows that PA-1 cells growing in TMSs are less susceptible to complement-mediated killing than cells growing in monolayer cultures, even after neutralization of protectin (CD59), the main inhibitor of complement lysis. Cells in suspension and cells growing in TMSs showed a similar expression of membrane co-factor protein (MCP, CD46) and CD59. Decay-accelerating factor (DAF, CD55) was not detected on the surface of cells in suspension, but appeared focally on the outermost cell layers of the TMSs. Complement-activating antibodies bound to all PA-1 cells in suspension but only to the most peripherally located cells in TMSs, even though the target antigens were similarly expressed in the two systems. Antibody-induced complement activation on PA-1 cells in suspension led to C3 and C5b-9 deposition on most cells, while C3 and C5b-9 were only found on the outermost layers of the TMSs. The increased complement resistance of tumour cells growing in threedimensional spheroids is partly because of an insufficient penetration of antibodies and complement into the TMSs. TMSs are a useful model for the development of more efficient ways to kill malignant cells in micrometastases with monoclonal antibodies and complement.

Ascitic complement system in ovarian cancer

“…The expression of membrane bound C regulators on tumour cells and the release of C regulators may at least partly explain the resistance. In addition, aggregated malignant cells are more difficult to kill by C than single cells (Bjrge L et al, 1997b;Hakulinen and Meri, 1998), further contributing to the tumour escape.…”

Three-dimensional and co-culture models for preclinical evaluation of metal-based anticancer drugs

“…This method allowed us to grow single spheroids per well in the 96-well format with a proper control of spheroid size. The used cell lines HCT116 (colon carcinoma), CH1(PA-1) (ovarian teratocarcinoma) and HT1080 (fibrosarcoma) were previously described in the literature to form compact, round shaped spheroids [29][30][31].…”

Folate receptor-targeted immunotherapy: Induction of humoral and cellular immunity against hapten-decorated cancer cells

“…Complement-dependent cytotoxicity was not expected to be a major contributor to the immunotherapy of the M109 solid tumors, because complement proteins do not readily perfuse solid tumors, 34 because solid tumors often express regulatory proteins that can inactivate complement 27,35 and because solid tumors may secrete soluble inhibitors of complement. 28 Thus, our inability to obtain evidence for complement participation in the folate-FITC/ anti-FITC IgG-mediated cytotoxicity was not surprising.…”