Rosalva Rangel-Corona

Evidence that cervical cancer cells secrete IL-2, which becomes an autocrine growth factor.

We present evidence that cervical cancer cells express a functional IL-2 receptor (IL-2R). In fact, by RT-PCR we obtained that the IL-2R is present in CALO, and INBL cells, and that it consisted of the alphaIL-2R, betaIL-2R, and gammaIL-2R chains. We also found that IL-2 is a growth factor for these cell lines, and unexpectedly that CALO and INBL themselves being cancer cells produce, and secrete IL-2. Antibodies against the alpha and beta subunits of the IL-2R inhibited cell proliferation thus hinting to a cell growth dependency on this factor. Our results thus provide evidence that the IL-2R on cervical cancer cells is part of an autocrine mechanism for its growth to the extent that, like lymphocytes, they produce and become partially dependent on this growth factor. We think that in view of our results caution should be taken when IL-2 is being considered for cancer therapy; in particular when the patients cancer cells present the IL-2R, because as indicated by our results, the use of this factor could promote tumor growth. Finally, the possible implications of the expression of both IL-2, and IL-2R on cervical cancer cells on the immune escape mechanism of tumor cells are discussed.

Cationic liposomes bearing IL-2 on their external surface induced mice leukocytes to kill human cervical cancer cells in vitro, and significantly reduced tumor burden in immunodepressed mice

Tumor cells are known to modify their surroundings in order to escape immunologic detection, and IL-2, a killer cell activator, is one of the factors known to overcome this escape mechanism. In this regard, when we cocultured cells from the human cervical cancer cell line INBL with mice blood leukocytes, no inhibition of tumor cell growth was observed, but when a similar coculture was done in the presence of cationic liposomes bearing IL-2 on their external surface (CL-IL-2), all the INBL cells were killed. In order to evaluate whether this in vitro property of CL-IL-2 to overcome tumor cell detection by lymphocytes could also be reproduced in vivo, INBL cells were intraperitoneally (i.p.) inoculated into immunodepressed mice to produce solid tumors. We observed that the subsequent i.p. delivery of CL-IL-2 rendered the tumor masses significantly smaller. The presence of a large number of infiltrating lymphocytes on those tumors, and the fact that many had a cytotoxic CD8+ phenotype suggests that these lymphocytes were responsible for the observed antitumor effect. Finally, the possible formation of a bridge between the IL-2R receptors on both, the lymphocytes and the INBL cells, mediated by the IL-2-bearing liposomes, and its possible effect on the activation of antitumor cytotoxic lymphocytes is discussed.

Characterization of cationic liposomes having IL-2 expressed on their external surface, and their affinity to cervical cancer cells expressing the IL-2 receptor

Anionic, cationic, and neutral liposomes were constructed to contain IL-2 in order to evaluate their affinity to a cervical cancer cell line (INBL) and to determine whether they can present IL-2 on their external surface. When these liposomes were co-cultured with INBL, the anionic liposomes were the only ones found to be cytotoxic. When neutral and cationic liposomes were constructed in the presence of IL-2, IL-2 was detected only on the surface of cationic liposomes by using a fluorescent anti-IL-2 antibody. By co-culturing INBL with IL-2-containing cationic liposomes, and by using fluorescent anti-IL-2 antibody, we found a strong IL-2 presence on the cell membranes thus suggesting a high affinity of the liposomes to the INBL cells.

The Tyrphostin B42 Inhibits Cell Proliferation and HER-2 Autophosphorylation in Cervical Carcinoma Cell Lines

The HER family receptors have an important role controlling cell growth and differentiation. Although the activity of the HER-2 receptor is strictly controlled in normal cells, its overexpression plays a pivotal role in transformation and tumorigenesis. Constitutive phosphorylation of HER-2 protein has been implicated in conferring uncontrolled growth to mammary cancer cells, and to a lesser extent, with adenocarcinoma of uterus, cervix, fallopian tube, and endometrium. This study addresses the role of HER-2 in cervical carcinoma. Firstly, we demonstrate the presence of HER-2 protein expression by flow cytometry in two new cervical carcinoma cell lines CALO and INBL. Secondly, we use the specific tyrosine kinase inhibitors, Tyrphostins to examine HER-2 regulation by the crystal violet assay. Thirdly, we use western blot analysis to assess the state of HER-2 phosphorylation. The most efficient agent, Tyrphostin B42, known as an inhibitor of epithelial growth factor receptor, arrested cervical carcinoma cell lines growth in vitro at micromolar concentrations within 72 h of application. Tyrphostin B42 inhibited the HER2 signal-regulated kinase pathway, as observed by the reduction in the phosphorylated forms of HER2. The loss of phosphorylated forms of HER2 at early time points after Tyrphostin B42 application was associated with suppression of cell growth. Thus, the inhibition of the proliferation of our cervical carcinoma cell lines by Tyrphostin B42 is associated with inhibition of HER2 protein kinase signal.