Establishment and characterization of a primary and a metastatic melanoma cell line from Grey horses

Abstract

The Grey horse phenotype, caused by a 4.6 kb duplication in Syntaxin 17, is strongly associated with high incidence of melanoma. In contrast to most human melanomas with an early onset of metastasis, the Grey horse melanomas have an extended period of benign growth, after which 50% or more eventually undergo progression and may metastasize. In efforts to define changes occurring during Grey horse melanoma progression, we established an in vitro model comprised of two cell lines, HoMel-L1 and HoMel-A1, representing a primary and a metastatic stage of the melanoma, respectively. The cell lines were examined for their growth and morphological characteristics, in vitro and in vivo oncogenic potential, chromosome numbers, and expression of melanocytic antigens and tumor suppressors. Both cell lines exhibited malignant characteristics; however, the metastatic HoMel-A1 showed a more aggressive phenotype characterized by higher proliferation rates, invasiveness, and a stronger tumorigenic potential both in vitro and in vivo. HoMel-A1 displayed a near-haploid karyotype, whereas HoMel-L1 was near-diploid. The cell lines expressed melanocytic lineage markers such as TYR, TRP1, MITF, PMEL, ASIP, MC1R, POMC, and KIT. The tumor suppressor p53 was strongly expressed in both cell lines, while the tumor suppressors p16 and PTEN were absent in HoMel-A1, potentially implicating significance of these pathways in the melanoma progression. This in vitro model system will not only aid in understanding of the Grey horse melanoma pathogenesis, but also in unraveling the steps during melanoma progression in general as well as being an invaluable tool for development of new therapeutic strategies.

Inherent variability of cancer-specific aneuploidy generates metastases

“…But ploidy variation in cancer cells is typically not exactly even, and is another independent characteristic of cancer cells that may increase or decrease oncogenicity by changing the dosage of genes evenly and non-evenly [76, 77, 112–114]. Its occurrence also seems to be proportional to the degree of cancer-specific aneuploidy [76, 115].…”

Constitutive activation of the ERK pathway in melanoma and skin melanocytes in Grey horses

“…50.5% ±13.0 in MITF + cells of the respective melanoma type; Figure 1 A, B). In line with the elevated P-ERK1/2 levels in the GHM tissues, high P-ERK1/2 levels were detected in two GHM cell lines, HoMel-L1 and HoMel-A1, established from a primary and metastatic melanoma tumour of a Grey Lipizzaner and Arabian horse, respectively [ 24 ]. The P-ERK1/2 levels were comparable to those seen in human melanoma cell lines with oncogenic BRAF or NRAS mutations, in contrast to a cell line with wild-type BRAF and NRAS (Figure 1 C, D; Table 1 ).…”

<b>Avaliação da cimetidina como tratamento de melanomas em equinos tordilhos</b>

“…De maneira geral, melanomas em animais tordilhos não são invasivos e aumentam seu tamanho muito lentamente ou demonstram "dormência" por longos períodos (McFADYEAN, 1933;SELTENHAMMER et al, 2003). Na maioria dos casos, os tumores apresentam-se encapsulados e nunca metastatizam, embora, em certas ocasiões, estas formações possam metastatizar tardiamente, tornando-se letais (SELTENHAMMER et al, 2003 (SAMS et al, 1997).…”

“…Uma série de estudos realizados em diversas raças demonstram que os locais mais comuns de aparecimento dos tumores são a região ventral da cauda e a região perineal, seguidas pelo prepúcio, comissura labial e pálpebras (FLEURY et al, 2000a;SELTENHAMMER et al, 2003;TEIXEIRA et al, 2013).…”

“…e adesão e maior tamanho de tumor(SELTENHAMMER et al, 2014). Devido à dificuldade de diagnosticar o grau de malignidade em proliferações melanocíticas de equinos, a pesquisa por um marcador molecular de malignidade tornou-se extremamente importante.…”