5-Aza-2'-Deoxycitidine induces growth-inhibition and up-regulation of epidermal-growth factor receptor on human epithelial cancer-cells

BACKGROUND: The epidermal growth factor (EGF-R) receptor is an important growth regulator of epithelial cancer cells, and is presently considered a tumor-associated antigen (TAA) which is overexpressed by several human cancers and barely detectable in most normal tissues. Since TAA density at the tumor cell surface is a critical factor regulating the efficiency of immunotargeting procedures, a therapeutic advantage may derive from the pharmacologic enhancement of membrane expression of such antigens on tumor cells. MATERIALS AND METHODS: Utilizing a panel of different human cancer cell lines of epithelial derivation, we have investigated in the in vitro effects of 5-aza-2'-deoxycytidine (5azaCdR), an antineoplastic agent able to induce gene activation and phenotypic modulation, on the surface expression of EGF-R by tumor cells. RESULTS: 5azaCdR (10-1000 nM) induced growth inhibition, in the absence of acute cell kill, on KB (human oropharyngeal carcinoma), LoVo and the drug-resistant clone LoVo-DX (colon carcinoma) and A549 (lung adenocarcinoma) cell lines, along with a significant enhancement of EGF-R expression at the tumor cell surface. A single 24 h pulse of 5azaCdR, followed by 96 h of culture in drug-free medium, induced 50% growth inhibition on KB cells at a concentration (IC50) of 500 nM, on A549 (IC50 = 490 nM), LoVo (IC50 = 400 nM) and LoVo-DX (IC50 = 100 nM) cell lines. Under these conditions the specific binding of 125I-EGF was significantly upregulated at the surface of growth-inhibited cancer cells. Scatchard analysis of EGF-binding data revealed no changes in the Kd of EGF-R for its ligand in 5azaCdR-treated tumor cells and demonstrated a significant increase in the number of both the high- and low-affinity EGF-binding sites on KB cells, while only one class of EGF-binding site was detectable on A549, LoVo and LoVo-DX tumor cell lines before and after exposure to 5azaCdR. The EGF-R upregulation induced by 5azaCdR was paralleled by the increased binding of the anti-EGF-R monoclonal antibody (MAb) 108.1 on the surface of cancer cells. Finally, the rate of endocytosis of the anti-EGF-R MAb by KB cells was not modified by drug treatment, indicating that exposure to 5azaCdR does not hamper MAb internalization by the tumor cells. This latter represents an essential process for the cytotoxic effects of immunoconjugate drugs or toxins. CONCLUSIONS: We suggest a role for 5azaCdR in enhancing the efficacy of therapeutic approaches involving the use of anti-EGF-R immunoconjugated for the imaging and the treatment of human epithelial neoplasias

Synergistic antitumor activity of epidermal growth factor receptor tyrosine kinase inhibitor gefitinib and IFN-A in head and neck cancer cells in vitro and in vivo

PURPOSE: Epidermal growth factor receptor (EGFR) overexpression has been implicated in the development of head and neck squamous cell carcinomas (HNSCC) and represents a potential therapeutic target for this disease. We have reported previously that growth inhibitory concentrations of IFN-alpha enhance the expression and activity of EGFR and that this effect could represent an escape mechanism to the growth inhibition and apoptotic cell death induced by IFN-alpha. In this study, we investigate whether the combination of IFN-alpha and gefitinib (Iressa, AstraZeneca Pharmaceuticals, Macclesfield, United Kingdom), a selective EGFR tyrosine kinase inhibitor, might have a cooperative antitumor effect on HNSCC-derived cell lines. EXPERIMENTAL DESIGN: The interaction of IFN-alpha and gefitinib was evaluated in vitro on HNSCC-derived cell lines by median drug effect analysis calculating a combination index with CalcuSyn software and in vivo by using HNSCC xenografts in nude mice. The mechanism of gefitinib and IFN-alpha interactions was also studied by analysis of cell cycle kinetics, apoptosis assays, and Western blotting of EGFR signal transduction components. RESULTS: Simultaneous exposure to gefitinib and IFN-alpha produced synergistic antiproliferative and proapoptotic effects compared with single drug treatment. Furthermore, daily treatment of gefitinib (50 mg/kg p.o.) in combination with an IFN-alpha regimen (50,000 units s.c. three times weekly) induced tumor growth delay and increased survival rate on established HNSCC xenografts in nude mice. Moreover, the concomitant treatment with gefitinib suppressed the stimulation of extracellular signal-regulated kinase phosphorylation/activity induced by IFN-alpha both in vitro and in vivo. CONCLUSION: The observed cooperative antitumor effects could be, at least in part, explained by the inhibition exerted by gefitinib of an IFN-alpha-induced EGF-dependent survival pathway, which involves extracellular signal-regulated kinase activation. These results provide a rationale for the clinical evaluation of gefitinib in combination with IFN-alpha in HNSCC

Phorbol 12-Myristate 13-Acetate (PMA) induces neuroendocrine-like differentiation and reverses doxorubicin-resistence of human colon-carcinoma cells in-vitro.

Human colon carcinoma LoVo/DX cells, which have been selected from parental LoVo for resistance to doxorubicin, express a typical multidrug resistant (MDR-1) phenotype. We have investigated whether phorbol 12-myristate 13-acetate (PMA) which often induces phenotypical changes in human tumor cells could, at the same time, modulate differentiation and sensitivity of LoVo/DX cells to doxorubicin. After 48 h exposure to 100 nM PMA, morphological changes became evident on LoVo/DX cells which showed elongated cytoplasm and dendritic-like structures: moreover immunocytochemical findings were suggestive of neuroendocrine-like differentiation. Under the same experimental conditions, LoVo/DX became sensitive to doxorubicin and showed enhanced intracellular drug-accumulation and reduced membrane expression of the 170 kD glycoprotein GP-170, which is the cellular product of the mdr1 gene. We conclude that pharmacological induction of tumor cell differentiation by PMA is paralleled by abrogation of drug resistance in a colon carcinoma MDR-1 cell line