Differential sensitivity to non-major histocompatibility complex-restricted recombinant interleukin 2-activated lymphocyte killing of human mammary epithelial MCF-10A cells overexpressing oncogenes or protein kinase A subunits

The sensitivity of human tumor cells to activated lymphocytes is considered to play an essential role in the antitumor activity of recombinant interleukin-2 (rIL-2)-based immunotherapy. We have investigated the effects of several genes involved in the regulation of cell growth and transformation on the sensitivity of human mammary epithelial MCF-10A cells to non-MHC-restricted, rIL-2-activated lymphocytes. Therefore, the lysability of MCF-10A cells overexpressing activated oncogenes (Ha-ras, erbB-2, and a mutated p53), growth factors [transforming growth factor alpha (TGFalpha)], or cAMP-dependent protein kinase A subunits (RIalpha, RIIbeta, and Calpha) was evaluated comparatively at different effector:target ratios by a 51Cr release assay. Parental MCF-10A, MCF-10A p53-mutated, and MCF-10A RIIbeta cells showed an intermediate sensitivity. Lysability was increased significantly in MCF-10A Ha-ras, MCF-10A TGFalpha, and MCF-10A RIalpha cells, reduced in MCF-10A Calpha cells, and completely abrogated in MCF-10A erbB-2 cells. These differences could not be explained by simple changes in the cell surface expression of MHC class I and intercellular adhesion molecule-1 proteins or by secretion of TGFbeta. Treatment with TAb 250, a mouse anti-p185(erbB-2) monoclonal antibody, or down-regulation of p185(erbB-2) expression resulted in circumvention of MCF-10A erbB-2 cell resistance. We conclude that molecular changes at the single-gene level resulting in alterations of intracellular signaling and/or cell transformation modulate sensitivity of human mammary epithelial cells to non-MHC-restricted, rIL-2-induced cytotoxicity, regardless of MHC class I and/or intercellular adhesion molecule-1 expression or TGFbeta secretion. Furthermore, anti-p185(erbB-2) monoclonal antibodies may be useful as adjuncts to rIL-2 treatment in patients with erbB-2-overexpressing tumors.