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 I

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 a (TGFa)], or cAMP-dependent protein kinase A subunits (RIa, RIII3, and Ca) was evaluated comparatively at different effector:target ratios by a SlCr release assay. Parental MCF-10A, MCF-10A p53-mutated, and MCF-10A RII[~ cells showed an intermediate sensitivity. Lysability was increased significantly in MCF-10A Ha-ras, MCF-10A TGFa , and MCF-10A R I a cells, reduced in MCF-10A C a 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 TGFI3. 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 TGFI3 secretion. Furthermore, anti-p185 erbB-2 monoclonal antibodies may be useful as adjuncts to rIL-2 treatment in patients with erbB-2overexpressing tumors. I N T R O D U C T I O N Non-MHC-restricted cytotoxic lymphocytes play an important role in the surveillance against tumor development (1). NK 3 cells, which represent 5-15% of circulating lymphocytes, are capable of killing several tumor cell targets without previous activation and in a non-MHC-restricted fashion. (1). LAK activity is generated on PBLs by IL-2 treatment. These lymphocytes, after ex vivo exposure to rlL-2, acquire the capacity of killing autologous and allogeneic tumor cells. LAK cytotoxicity is non-MHC restricted, resides mostly in NK cells, and can be exerted also against tumor cell targets not sensitive to spontaneous NK cytotoxicity. LAK activity can be generated and transferred adoptively to cancer patients by rlL-2 administration (2). Cultured human tumor cells are heterogeneous in their in vitro sensitivity to cell-mediated cytotoxicity and specifically to NK and LAK effectors. Such a difference has been ascribed to various cancer cell phenotypes, including the degree of differentiation (3), the expression of adhesion molecules (4, 5) and MHC class I antigens (6, 7), and the production of immunodepressing factors such as TGFI3 (8, 9). It is a common finding that molecular changes leading to cell transformation induce an increased sensitivity to non-MHCrestricted cytotoxicity. Oncogene expression has been correlated to changes in NK and LAK sensitivity. In this respect, v-Ki-ras transformation increases the sensitivity of Rat-1 fibroblasts to NK cells (10). Expression of an activated, point-mutated c-Haras oncogene is capable of enhancing the susceptibility of mouse C3H 10T1/2 cells to NK cytolysis (11). On the other hand, it has been shown that transfection of human colon carReceived 5/15/95; revised 8/11/95; accepted 8/15/95. Supported by the Italian Association for Cancer Research; Consiglio Nazionale della Ricerca, Progetto Finalizzaro: Applicazioni Cliniche della Ricerca Oncologica; the Elsa U. Pardee Foundation; and NIH Grant CA162212-01A1. M. C. and A. R. are recipients of fellowships from the Italian Association for Cancer Research. 2 To whom requests for reprints should be addressed. 3 The abbreviations used are: NK, natural killer; TGF, transforming growth factor; PKA, protein kinase A; MAb, monoclonal antibody; PBL, peripheral blood lymphocyte; ICAM-1, intercellular adhesion molecule-l; LAK, lymphokine-activated killing; rlL-2, recombinant interleukin-2; EGF, epidermal growth factor; MT-1, metallothionein-1; mut, mutated; FBS, fetal bovine serum; IU, international unit; FACS, fluorescence-activated cell sorting. Cancer Research. on September 22, 2017. © 1996 American Association for clincancerres.aacrjournals.org Downloaded from 208 Oncogenes and PKA Subunits Modulate LAK Sensitivity cinoma cells with a c-Ha-ras oncogene leads to the acquisition of NK resistance (12). Expression of c-erbB-2 correlates generally with resistance to LAK in human ovarian tumor cell lines (13). This information has been derived generally from studies in which rodent cell systems or human tumor cell lines have been used. Taking into account the complexity of genetic events causing human carcinogenesis, it is difficult to obtain useful information on the specific role of single oncogenes in the determination of lymphocyte sensitivity by comparative studies on human cultured tumor cell lines. Furthermore, rodent cell systems are derived from phenotypically unstable fibroblast cell lines, such as NIH-3T3 cells, which could be transformed easily by a chemical agent or by a single activated oncogene. These systems have been used successfully for the identification of activated oncogenes by transfection assays. However, they are generally of limited value for the study of phenotypical changes correlated to the modifications in the sensitivity to activated lymphocytes. In this regard, we have taken advantage of the recent establishment of MCF-10A cells, which have unique characteristics of nontransformed, spontaneously immortalized, human mammary epithelial cells (14). We developed several MCF-10A clones transformed following transfection or infection with appropriate expression vectors containing activated oncogenes, such as Ha-ras, mutated tumor suppressor genes, such as a mutated p53, growth factor genes, such as TGFoL, and growth factor receptor genes, such as erbB-2 (15-17). Furthermore, we have obtained MCF-10A clones that overexpress the various PKA genes recently (18). This provides a useful in vitro model system for studying the mechanisms of human mammary epithelial cell transformation. In this study, we have evaluated the sensitivity of various MCF-10A derivatives to rIL-2-activated human lymphocytes in a 5~Cr release cytotoxicity assay. A definite pattern of sensitivity to rIL-2-activated lymphocytes was observed. Therefore, we have investigated whether changes in the expression of surface molecules, such as MHC class I and ICAM-1, or of secreted factors, such as TGF[3, could account for the differences in the sensitivity to rlL-2-activated lymphocytes observed in the various MCF-10A cell lines. Because the highest degree of resistance was observed in MCF-10A erbB-2, we have evaluated whether treatment with an anti-p185 erbB-2 mouse MAb or p185 erbB-2 down-regulation could increase the sensitivity of these cells to activated lymphocytes. MATERIALS AND METHODS Cell Cultures. MCF-10A cells and their derivatives were grown in a 1:1 (v/v) DMEM and Ham's F12 medium (Flow Laboratories, Milan, Italy) mixture supplemented with 5% heatinactivated horse serum, 20 mM HEPES (pH 7.4), 4 mM glutamine, 0.5 txg/ml hydrocortisone, 10 ng/ml EGF, and 10 Ixg/ml insulin. MCF-10A Ha-ras cells were generated by cotransfection of MCF-10A cells with an expression vector plasmid containing the human activated c-Ha-ras proto-oncogene and an expression vector plasmid containing the neomycin resistance gene (15). MCF-10A neo cells are MCF-10A cells containing only the neomycin resistance gene. MCF-10A TGFoL, MCF-10A CoL, MCF-10A RIa, and MCF-10A RII[3 cells were obtained by infection of MCF-10A cells with amphotropic retroviral vectors containing the neomycin resistance gene with the human TGFoL, Ca, Riot, and RIIf3 genes (15, 18). MCF-10A erbB-2 cells were generated following infection of MCF-10A cells with an amphotropic retroviral vector containing the hygromycin resistance gene with the human c-erbB-2 proto-oncogene (16). Expression of these genes was under the transcriptional control of the heavy metal-inducible mouse MT-1 promoter. Therefore, MCF-10A TGFa, MCF-10A Ca, MCF-10A RIoL, MCF-10A RII[3, and MCF-10A erbB-2 cells were grown continuously in the presence of 1 p~M CdC12 to induce the expression of the MT-1 promoter maximally. We have shown previously that this concentration of CdC12 is not toxic for MCF-10A cells and does not affect their growth (15). MCF-10A p53 mut cells were generated by transfection of MCF-10A cells with an expression vector plasmid containing the puromycin resistance gene with a human-mutated p53 gene containing a point mutation at codon 238 with a cysteine-to-phenylalanine substitution, as described previously (17). The expression of each transduced gene in the various MCF-10A cell derivatives was assessed properly (1518). The human tumor cell line SKOV-3 was obtained from the American Type Culture Collection (Rockville, MD; cell line HTB77) and was grown in Iscove's DMEM containing 10% FBS and 2 mM L-glutamine (19). All cell lines were maintained in a humidified incubator with 5% CO 2 at 37°C. Cell-mediated Cytotoxieity. The sensitivity of MCF10A-derived cell lines by LAK cells was evaluated in a 5~Cr release cytotoxicity assay at different effector:target ratios in complete medium containing heat-inactivated 10% FBS. Target cells were seeded in 96-multiwell plates (Becton Dickinson, Lincoln Park, NJ) and incubated with 51Cr (37 megabecquerels, 1.00 mCi; Amersham, Buckinghamshire, United Kingdom; 30,000-50,000 cpm/well) for 30 min at 37°C. PBLs obtained by Ficoll-hypaque gradient separation were incubated in RPMI 1640 medium with 10% FBS, L-glutamine, and antibiotics, rIL-2 (1,000 IU/ml; Cetus Corp., Emeryville, CA) was added subsequently, and the PBLs were incubated at 37°C for 18 h. IL-2 treatment of human PBL, under these conditions, induces LAK activity, which seems to be mostly due to activated NK cells (20). Parallel experiments were conducted with LAK cells generated by exposure to 100 IU rIL-2 for 5 days. After washing with PBS without Ca 2+ and Mg ++, LAK cells were added to the dishes at different effector:target ratios. Target cells and immune effectors were incubated at 37°C for 4 h. One hundred Ixl supernatant medium from each of triplicate samples were counted in a gamma counter (Beckman Instruments, Fullerton, CA). Results were expressed as percentage specific release: