Establishment and characterization of an oral melanoma cell line (ME)

Novel cellular systems unveil mucosal melanoma initiating cells and a role for PI3K/Akt/mTOR pathway in mucosal melanoma fitness

BACKGROUND

Mucosal Melanomas (MM) are highly aggressive neoplasms arising from mucosal melanocytes. Current treatments offer a limited survival benefit for patients with advanced MM; moreover, the lack of pre-clinical cellular systems has significantly limited the understanding of their immunobiology.

METHODS

Five novel cell lines were obtained from patient-derived biopsies of MM arising in the sino-nasal mucosa and designated as SN-MM1-5. The morphology, ultrastructure and melanocytic identity of SN-MM cell lines were validated by transmission electron microscopy and immunohistochemistry. Moreover, in vivo tumorigenicity of SN-MM1-5 was tested by subcutaneous injection in NOD/SCID mice. Molecular characterization of SN-MM cell lines was performed by a mass-spectrometry proteomic approach, and their sensitivity to PI3K chemical inhibitor LY294002 was validated by Akt activation, measured by pAkt(Ser473) and pAkt(Thr308) in immunoblots, and MTS assay.

RESULTS

This study reports the validation and functional characterization of five newly generated SN-MM cell lines. Compared to the normal counterpart, the proteomic profile of SN-MM is consistent with transformed melanocytes showing a heterogeneous degree of melanocytic differentiation and activation of cancer-related pathways. All SN-MM cell lines resulted tumorigenic in vivo and display recurrent structural variants according to aCGH analysis. Of relevance, the microscopic analysis of the corresponding xenotransplants allowed the identification of clusters of MITF-/CDH1-/CDH2 + /ZEB1 + /CD271 + cells, supporting the existence of melanoma-initiating cells also in MM, as confirmed in clinical samples. In vitro, SN-MM cell lines were sensitive to cisplatin, but not to temozolomide. Moreover, the proteomic analysis of SN-MM cell lines revealed that RICTOR, a subunit of mTORC2 complex, is the most significantly activated upstream regulator, suggesting a relevant role for the PI3K-Akt-mTOR pathway in these neoplasms. Consistently, phosphorylation of NDRG1 and Akt activation was observed in SN-MM, the latter being constitutive and sustained by PTEN loss in SN-MM2 and SN-MM3. The cell viability impairment induced by LY294002 confirmed a functional role for the PI3K-Akt-mTOR pathway in SN-MM cell lines.

CONCLUSIONS

Overall, these novel and unique cellular systems represent relevant experimental tools for a better understanding of the biology of these neoplasms and, as an extension, to MM from other sites.

CDK4 and TERT amplification in head and neck mucosal melanoma

BACKGROUND

Recent high-throughput sequencing studies have revealed frequent CDK4 and TERT amplification in mucosal melanoma, suggesting that they are potential therapeutic targets. In this study, we investigated the statuses of CDK4 and TERT in head and neck mucosal melanoma (HNMM) with the aim of providing preclinical data to support future clinical trials.

METHODS

In total, 29 HNMM samples were collected, including 16 oral mucosal melanoma (OMM) samples and 13 nasal cavity/sinuses melanoma (SNMM) samples. Fluorescence in situ hybridization was used to analyze CDK4 and TERT amplification, and immunohistochemistry was used to analyze CDK4 and TERT protein expression patterns. CDK4 expression was knocked down in the ME cells (an OMM cell line), and changes in cell cycle were analyzed. Cell viability assays were performed to determine the sensitivity of ME to abemaciclib (a CDK4 inhibitor) combined with dacarbazine (an anti-melanoma chemotherapy drug).

RESULTS

We detected five samples exhibited CDK4 amplifications and nine samples exhibited TERT amplifications in our HNMM series, and found that CDK4 amplification tended to occur in combination with TERT amplification. Amplifications of CDK4 and TERT were more common in OMM than in SNMM. Amplifications of CDK4 and TERT were associated with greater CDK4 and TERT protein expression levels. CDK4 knockdown led to delayed G1/S phase transition in ME cells. Furthermore, ME cells were sensitive to abemaciclib (IC₅₀  = 5.23 nM). Abemaciclib and dacarbazine synergistically inhibited ME cells' viability.

CONCLUSION

We confirmed high frequencies of CDK4 and TERT amplification in OMM. Combined therapy with a CDK4/6 inhibitor and anti-melanoma chemotherapeutic agents will be a reasonable strategy for future clinical trials concerning unresectable or metastatic OMM.

Establishment and characterization of an oral mucosal melanoma cell line (MEMO) derived from a longstanding primary oral melanoma

Oral mucosal melanoma is rare. Its incidence peaks between 41 and 60 years of age; male/female ratio is 2:1. Preferred oral sites include hard palate and maxillary gingiva. Risk factors have not been clearly identified, but pigmented lesions may be present before the diagnosis of oral melanoma. We report an unusual case of oral mucosal melanoma of long-standing duration on hard palate and maxillary alveolar ridge in a male patient. Histopathologic features confirmed the diagnosis of invasive melanoma with a prominent in situ component. A cell lineage derived from the tumor was established and characterized, with phenotypic markers of melanocytes.

Oral malignant melanoma diagnosed in an Iranian population over an 11-year period

OBJECTIVE

The aim of this study was to determine the prevalence of oral malignant melanoma along with age range and site of presentation over an 11-year period in Iran.

MATERIALS AND METHODS

The files of Tehran Cancer Institute served as a source of material for this study. Files were systematically searched for all malignant melanomas and oral malignant melanomas during an 11-year period. Prepared slides and demographic data from the biopsy files were reviewed. Statistical analysis was performed with the use of SPSS.

RESULTS

Of the 38,993 cases accessed during the 11-year period, 569 were identified as malignant melanomas, while 41 cases among this group had malignant oral melanomas comprising 0.1% of the total cases and 7.2% of all the malignant melanoma lesions.

CONCLUSION

The palate was the most common location for oral malignant melanoma. Thus, all melanocytic lesions in the palate should be viewed with caution, and biopsy is recommended to rule out melanoma.

Establishment and characterization of a cell line (DEOC-1) originating from a human malignant melanoma of the skin

A new human malignant melanoma cell line, designated DEOC-1, was established from the heel lesion of a 59-year-old man. This cell line has grown well for 84 months. The monolayer, cultured cells are polygonal in shape, appear to be spindle-shaped cells or multipolar cells, and have a tendency to pile up without contact inhibition. The cells are aneuploid, and the modal chromosomal number is in the hyper-triploid range. The cells were transplanted into the subcutis of SCID mice and produced tumors resembling the original tumor. The DEOC-1 cells (1 x 10(6)/5 mL) produced 5-S-cysteinyldopa (5-S-CD). The cells were not sensitive in vitro to any anticancer drug currently used for the treatment of malignant melanoma. Increases in both the protein and the transcriptional levels (mRNA) of multidrug resistance-related genes (multidrug resistance gene 1, multidrug resistance-associated protein 1 and lung resistance-related protein) were observed in DEOC-1 cells. The DEOC-1 cells are well characterized and are a very useful material for basic research of malignant melanoma.

Estudo genético do gene p16 pela técnica de PCR-SSCP e expressão de proteína p16 em melanomas de mucosa oral e melanomas cutâneos

FUNDAMENTOS: A deleção e mutação do gene CDKN2a que codifica um inibidor específico da ciclina dependente de quinase 4, a proteína p16, têm sido implicadas na tumorigênese do melanoma cutâneo. Entretanto, pouco se conhece sobre essas alterações genéticas em melanomas de mucosa oral. OBJETIVOS: Verificar a presença de alterações no gene p16 e sua expressão protéica em melanomas esporádicos orais e cutâneos. MATERIAL E MÉTODOS: Avaliaram-se 36 espécimes de melanoma primário (sete orais e 29 cutâneos). Analisaram-se três exons do gene p16, pela técnica da reação em cadeia da polimerase/polimorfismo conformacional de fita simples do DNA.Verificou-se a expressão tecidual de proteína p16 por técnica imuno-histoquímica. Relacionaram-se os resultados com a espessura dos melanomas cutâneos. RESULTADOS: Cinco dos sete melanomas orais e 17 dos 29 melanomas cutâneos apresentaram indício de alteração no gene p16. Alterações do exon 2 foram as mais freqüentes, sendo 19 casos nos produtos obtidos com o mesmo iniciador. Observou-se expressão tecidual de p16 em apenas um melanoma oral, em 10/13 (76,9%) casos de melanoma cutâneo de espessura até 1mm e em sete de oito (87,5%) casos de espessura superior a 1mm. CONCLUSÃO: A freqüência de indícios de alteração na análise genética de p16 nos melanomas de mucosa oral foi de 71,42% e de 58,6% nos cutâneos. É possível sugerir a participação de alterações do gene p16 na patogenia do melanoma esporádico de mucosa oral. Não houve relação da sugestão de alteração genética do gene p16 e de sua expressão tecidual com a espessura dos melanomas cutâneos de diferentes subtipos histológicos.

Distinct chromosomal aberrations in sinonasal mucosal melanoma as detected by comparative genomic hybridization

Sinonasal mucosal melanomas are the most frequent mucosal melanomas and arise from melanocytes located in the nasal cavity and the paranasal sinuses. The melanoma types, cutaneous melanoma, uveal melanoma, and mucosal melanoma, differ in etiology, geographic distribution, and clinical behavior. Genetic alterations have been previously studied in cutaneous and uveal melanomas but, to the best of our knowledge, not in mucosal melanomas. Comparative genomic hybridization (CGH) was performed on 14 routinely processed sinonasal mucosal melanomas. Furthermore, ploidy analysis was performed on 11 tumors to provide complementary data on the DNA index. The CGH profiles of sinonasal mucosal melanomas show remarkably consistent alterations: chromosome arm 1q is gained in all tumors and gains of 6p and 8q are present in 93 and 57%, respectively. Comparison of CGH data with both the common variants of cutaneous melanoma and uveal melanoma revealed that sinonasal mucosal melanomas harbor a distinct pattern of chromosomal abnormalities. Ploidy analysis also showed that diploid tumors exhibit gains of 1q and alterations of chromosome 6 (3 of 3 cases tested), whereas clear-copy gains and high-copy gains were seen only in triploid and tetraploid tumors (6 of 8 cases tested). This indicates that alteration of chromosomes 1 and 6 may precede polyploidization and formation of clear-copy gains and high-copy gains.