Epithelial-mesenchymal transition can suppress major attributes of human epithelial tumor-initiating cells.

Malignant progression in cancer requires populations of tumor-initiating cells (TICs) endowed with unlimited self renewal, survival under stress, and establishment of distant metastases. Additionally, the acquisition of invasive properties driven by epithelial-mesenchymal transition (EMT) is critical for the evolution of neoplastic cells into fully metastatic populations. Here, we characterize 2 human cellular models derived from prostate and bladder cancer cell lines to better understand the relationship between TIC and EMT programs in local invasiveness and distant metastasis. The model tumor subpopulations that expressed a strong epithelial gene program were enriched in highly metastatic TICs, while a second subpopulation with stable mesenchymal traits was impoverished in TICs. Constitutive overexpression of the transcription factor Snai1 in the epithelial/TIC-enriched populations engaged a mesenchymal gene program and suppressed their self renewal and metastatic phenotypes. Conversely, knockdown of EMT factors in the mesenchymal-like prostate cancer cell subpopulation caused a gain in epithelial features and properties of TICs. Both tumor cell subpopulations cooperated so that the nonmetastatic mesenchymal-like prostate cancer subpopulation enhanced the in vitro invasiveness of the metastatic epithelial subpopulation and, in vivo, promoted the escape of the latter from primary implantation sites and accelerated their metastatic colonization. Our models provide new insights into how dynamic interactions among epithelial, self-renewal, and mesenchymal gene programs determine the plasticity of epithelial TICs.

Molecular characterization of human cutaneous melanoma-derived cell lines.

BACKGROUND: Several studies have demonstrated that different genetic profiles contribute to melanoma development and progression. MATERIALS AND METHODS: To evaluate the existence of different molecular aberration patterns in melanoma associated with v-raf murine sarcoma viral oncogene homolog B1 (BRAF) or 9p21 locus alterations, eleven patient-derived melanoma cell lines were characterized. Multiplex ligation probe amplification (MLPA) was used to detect chromosomal alterations. Single- strand conformation analysis and sequencing were performed to study BRAF, neuroblastoma RAS viral (v-ras) oncogene homolog (NRAS), v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (c-KIT), melanocortin 1 receptor (alpha melanocyte stimulating hormone receptor) (MC1R), cyclin-dependent kinase inhibitor 2A (CDKN2A) and cyclin-dependent kinase 4 (CDK4) genes. RESULTS: BRAFV600E mutation was detected in 54% of cell lines. NRAS was mutated in one cell line also carrying multiple copies of NRAS. All cell lines with MC1R variants harboured BRAFV600E. Concurrent loss of MUTYH (1p33), gains of c-MYC (8q24) and of CDK6 (7q21) were found to be significantly associated in cell lines (45%) that harboured biallelic 9p21 deletions including CDKN2B-CDKN2A-MTAP. CONCLUSION: These data suggest the existence of a specific pattern of somatic alterations in genes that are involved in DNA repair (MUTYH) and in cell cycle regulation (c-MYC, CDK6, CDKN2A and CDKN2B). Interestingly, all MC1R variants were associated with BRAFV600E and all cell lines from visceral metastases harboured BRAFV600E.

Antiproliferative effect of STI571 on cultured human cutaneous melanoma-derived cell lines.

Standard antineoplastic treatment for metastatic melanoma is ineffective in the large majority of patients. Therefore, alternative approaches need to be investigated. STI571 is a new antineoplastic compound, which selectively inhibits the tyrosine kinase activity of ABL, c-Kit and platelet-derived growth factor receptor (PDGFR). Melanoma may express all of these proteins. The aim of this study was to investigate whether STI571 inhibits the in-vitro growth of melanoma cells. Nineteen cell lines were obtained from four primary and 15 metastatic melanomas of cutaneous origin. The percentages of positive cells for the putative targets of STI571 were as follows: ABL, 41-100%; c-Kit, 8-97%; PDGFR-alpha, 41-98%; PDGFR-beta, 51-99%. 3-(4,5-Dimethylthiazol-yl)-2,5-diphenyltetrazolium (MTT) and viability assays showed that STI571 clearly inhibits the proliferation of eight of the 19 (42.1%) cell lines. No relationship could be established between the expression of c-Kit, ABL, PDGFR-alpha or PDGFR-beta and the response of cell lines to STI571. Our study shows, for the first time, an antiproliferative effect of STI571 on human melanoma cell lines of cutaneous origin, raising the possibility of the future clinical use of STI571. The identification of the target of STI571 in human cutaneous melanoma cells would allow the selection of patients who could benefit from this treatment.

Treatment of patients with progressive unresectable metastatic melanoma with a heterologous polyvalent melanoma whole cell vaccine.

Unresectable metastatic melanoma has no elective treatment. Neither chemotherapy, intravenous IL-2 nor biochemotherapy clearly improves the overall survival. Recent assays with therapeutic vaccines have been recently yielded promising results. Here, we describe the application, clinical tolerance and antitumoural activity of a heterologous polyvalent melanoma whole cell vaccine in patients with metastatic melanoma. Twenty-eight AJCC stage III/IV melanoma patients with progressive unresectable metastatic disease were treated with our heterologous polyvalent melanoma whole cell vaccine between July 1, 1998 and July 1, 2002. All patients had already been unsuccessfully treated with high doses of IFN-alpha2 and/or polychemotherapy and/or biochemotherapy and/or perfusion of extremities, or could not receive other treatments due to their age or underlying illness. Twenty-three were assessable. The vaccine was constituted by 10 melanoma cell lines, derived from primary, lymph node and metastatic melanomas. Prior to intradermal inoculation, the cells were irradiated and mixed with BCG, and 50% were treated with DNFB. After a median follow-up of 19 months, 26% of patients responded: 3 CR (18, 16+, and 26+ months), 2 PR (8 and 22 months) and 1 MR (36+ months). The median survival of the whole group was 20.2 months. None of the 28 patients initially included in the study presented significant toxicity. This vaccination program had specific antitumoural activity in advanced metastatic melanoma patients and was well tolerated. The clinical responses and the median survival of our group of patients, together with the low toxicity of our polyvalent vaccine, suggest that this approach could be applied to earlier metastatic melanoma patients.