Cisplatin-based chemotherapy is the paradigm of non-smallcell lung cancer (NSCLC) treatment; however, it also induces de novo DNA-hypermethylation, a process that may be involved in the development of drug-resistant phenotypes by inactivating genes required for drug-cytotoxicity. By using an expression microarray analysis, we aimed to identify those genes reactivated in a set of two cisplatin (CDDP) resistant and sensitive NSCLC cell lines after epigenetic treatment. Gene expression, promoter methylation and CDDP-chemoresponse were further analyzed in three matched sets of sensitive/resistant cell lines, 23 human cancer cell lines and 36 NSCLC specimens. Results revealed specific silencing by promoter hypermethylation of IGFBP-3 in CDDP resistant cells, whereas IGFBP-3 siRNA interference, induced resistance to CDDP in sensitive cells (Po0.001). In addition, we found a strong correlation between methylation status and CDDP response in tumor specimens (Po0.001). Thus, stage I patients, whose tumors harbor an unmethylated promoter, had a trend towards increased disease-free survival (DFS). We report that a loss of IGFBP-3 expression, mediated by promoter-hypermethylation, results in a reduction of tumor cell sensitivity to cisplatin in NSCLC. Basal methylation status of IGFBP-3 before treatment may be a clinical biomarker and a predictor of the chemotherapy outcome, helping to identify patients who are most likely to benefit from CDDP therapy alone or in combination with epigenetic treatment.

Purpose: Mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) dephosphorylates mitogen-activated protein kinase [extracellular signal-regulated kinase (ERK), c-Jun NH 2 -terminal kinase (JNK), and p38], mediates breast cancer chemoresistance, and is repressible by doxorubicin in breast cancer cells. We aimed to characterize doxorubicin effects on MKP-1 and phospho-MAPKs in human breast cancers and to further study the clinical relevance of MKP-1 expression in this disease. Experimental Design: Doxorubicin effects on MKP-1, phospho-ERK1/2 (p-ERK1/2), phospho-JNK (p-JNK), and phospho-p38 were assayed in a panel of human breast cancer cells by Western blot and in human breast cancer were assayed ex vivo by immunohistochemistry (n = 50). MKP-1 expression was also assayed in a range of normal to malignant breast lesions (n = 30) and in a series of patients (n = 96) with breast cancer and clinical follow-up. Results: MKP-1 was expressed at low levels in normal breast and in usual ductal hyperplasia and at high levels in in situ carcinoma. MKP-1 was overexpressed in ∼50% of infiltrating breast carcinomas. Similar to what was observed in breast cancer cell lines, ex vivo exposure of breast tumors to doxorubicin down-regulated MKP-1, and upregulated p-ERK1/2 and p-JNK, in the majority of cases. However, in a proportion of tumors overexpressing MKP-1, doxorubicin did not significantly affect MKP-1 or phospho-MAPKs. With regard to patient outcome, MKP-1 overexpression was an adverse prognostic factor for relapse both by univariate (P < 0.001) and multivariate analysis (P = 0.002). Conclusions: MKP-1 is overexpressed during the malignant transformation of the breast and independently predicts poor prognosis. Furthermore, MKP-1 is repressed by doxorubicin in many human breast cancers.

Although many cancers initially respond to cisplatin (CDDP)-based chemotherapy, resistance frequently develops. Insulin-like growth factor-binding protein-3 (IGFBP-3) silencing by promoter methylation is involved in the CDDP-acquired resistance process in non-small cell lung cancer (NSCLC) patients. Our purpose is to design a translational-based profile to predict resistance in NSCLC by studying the role of IGFBP-3 in the phosphatidyl inositol 3-kinase (PI3K) signaling pathway. We have first examined the relationship between IGFBP-3 expression regulated by promoter methylation and activation of the epidermal growth factor receptor (EGFR), insulin-like growth factor-I receptor (IGFIR) and PI3K/AKT pathways in 10 human cancer cell lines and 25 NSCLC patients with known IGFBP-3 methylation status and response to CDDP. Then, to provide a helpful tool that enables clinicians to identify patients with a potential response to CDDP, we have calculated the association between our diagnostic test and the true outcome of analyzed samples in terms of cisplatin IC50; the inhibitory concentration that kills 50% of the cell population. Our results suggest that loss of IGFBP-3 expression by promoter methylation in tumor cells treated with CDDP may activate the PI3K/AKT pathway through the specific derepression of IGFIR signaling, inducing resistance to CDDP. This study also provides a predictive test for clinical practice with an accuracy and precision of 0.84 and 0.9, respectively, (P=0.0062). We present a biomarker test that could provide clinicians with a robust tool with which to decide on the use of CDDP, improving patient clinical outcomes.