Mutational landscape of oral mucosal melanoma based on comprehensive cancer genomic profiling tests in a Japanese cohort

OBJECTIVES

Oral mucosal melanoma (OMM) is a rare but aggressive melanoma subtype. Due to its rarity, the genomic landscape of OMM remains unknown despite a relatively thorough understanding of the genetic profile of cutaneous melanoma (CM). In this study, we analyzed the genomic mutational profiles of Japanese patients with OMM and compared them with those of patients with nose/sinuses mucosal melanoma (NMM) and CM to identify potential therapeutic targets.

MATERIALS AND METHODS

We extracted clinical and genomic information of patients with OMM (n = 15), NMM (n = 63), and CM (n = 413) who underwent comprehensive genomic profiling tests under the National Health Insurance between June 2019 and November 2023 from the Center for Cancer Genomics and Therapeutics database.

RESULTS

The most frequent genomic alteration identified in OMM was RICTOR (40%) followed by CDK4 (33.3%), MDM2 (33.3%), KDR (30%), KIT (26.7%), and NF1 (26.7%). CDK4 and MDM2 were co-amplified. Gene alterations in MYC and NRAS were the highest in patients with NMM, followed by those with CM, and no MYC alteration was observed in patients with OMM. BRAF V600 mutation, which is frequently observed in patients with CM (23.2%) were only present in 1.6% of patients with NMM and none in patients with OMM.

CONCLUSION

This study clarified the genetic differences between OMM and NMM, and the first to report the frequent occurrence of RICTOR amplification in OMM. This analysis offers insights into the development of personalized therapeutics for OMM.

Oral mucosal melanoma - A systematic review

Oral mucosal melanoma (OMM) is the subject of few studies, resulting in a lack of understanding. The aim of this study is to review the current literature on OMM. The term searched was "oral mucosal melanoma" between 01/01/2000 and 03/15/2021 in the PubMed Database (MEDLINE). Patients presenting with OMM and treated in our center between January 2009 and January 2020 were included in a case series. Demographics, location, risk factors, genetic mutations, treatment performed, and overall survival (OS) rates were evaluated. The PubMed database search yielded a total of 513 results, thirty-eight articles were finally included, which amounted to 2230 cases of OMM. 13 patients were included in the case series. A male-to-female ratio of 1.28:1.00 was found with a mean age at first diagnosis of 58.2 years old. Hard palate (1060 cases) and then gingiva (794 cases) were the two main locations. No risk factors could be identified. OMM were staged III or IV at diagnosis. Mutations were described as such: KIT in 14.6% of cases, BRAF in 7%, and NRAS in 5.6%. Treatment protocols varied but radical surgery was the cornerstone treatment associated with adjuvant therapies. Immunotherapy has not been evaluated for OMM. OS rates were 43.4% at 3 years, 33.1% at 5 year and 15.4% at 10 years. OMM show distinct features from cutaneous melanoma (CM): typical locations, no identified risk factors, different mutations profile, worse prognosis with advanced stage at diagnosis. Targeted therapies are still underused compared to CM.

Altered expression pattern of circular RNAs in metastatic oral mucosal melanoma

Circular RNAs (circRNAs) are known to be associated with carcinogenesis, and can serve as potential biomarkers for cancer diagnosis and therapeutic implications. However, little is known about their expression patterns in oral mucosal melanoma (OMM), an extremely rare cancer that is distinct from cutaneous melanoma for its clinical course and prognosis. To investigate circRNAs expression profile in OMM, we performed a circRNAs microarray to analyze 6 primary OMM samples with lymph nodes dissemination, and constructed a genome-wide circRNA profile. Our results revealed that 90 circRNAs were significantly dysregulated in the metastatic OMM tissues when compared to the paired adjacent tissues. Among them, hsa_circ_0005320, hsa_circ_0067531, hsa_circ_0008042 were significantly upregulated in primary tumor and metastatic lymph nodes compared to paired adjacent normal tissues and non-metastatic lymph nodes, whereas the expression of hsa_circ_0000869 and hsa_circ_0000853 were downregulated relatively. Gene Ontology (GO) and pathway analyses of differentially expressed circRNAs indicated that these identified circRNAs might play important roles in protein modification, protein binding and cellular metabolism in metastatic OMM. Functions of several selected circRNA were also identified. In addition, by using bioinformatics predictions, we further demonstrated that hsa_circ_0005320, hsa_circ_0067531 and hsa_circ_0000869 could serve as competing endogenous RNA (ceRNA), which might regulate tumorigenesis and metastatic of OMM by binding to specific microRNAs. Our results not only suggested that circRNAs might play critical roles in metastasis of OMM, but also provided critical information of circRNAs in regulating OMM progression. The findings would help us to develop potential biomarkers for clinical diagnosis and design therapeutic strategies for OMM.

A comprehensive genome-wide analysis of the long noncoding RNA expression profile in metastatic lymph nodes of oral mucosal melanoma

BACKGROUND & AIM

Oral mucosal melanoma (OMM) is a kind of malignancy with extremely rare morbidity. It exhibits a poorer biological behavior and clinical outcome compared with cutaneous melanoma. lncRNAs are endogenous cellular RNA transcripts with no protein-coding potential and are associated with oncogenesis through cis- or trans-acting mechanisms. Despite increased evidence that proved lncRNAs have vital roles in tumorigenesis of mucosal melanoma, little is known about their functions in the progress of lymph node dissemination of OMM.

METHOD

Here, we constructed a lncRNA and mRNA microarray using six metastatic lymph nodes and paired-matched non-metastatic lymph nodes. Then, we performed RT-PCR to validate the microarray data both in primary and metastases. We further constructed lncRNA and mRNA co-expressing networks and analyzed the biological functions by Gene Ontology (GO) and pathway analyses for dysregulated lncRNAs and mRNAs. Cis- and trans-regulation analysis were also performed to explore the specific mechanism of lncRNAs in OMM.

RESULT

Our results showed that 570 lncRNAs were upregulated with 292 lncRNAs downregulated in the metastatic OMM tissues. The results of RT-PCR were consistent with our microarray dataset both in primary and metastases. Gene Ontology (GO) and pathway analyses indicated that they play an important role in the melanin biosynthetic process, new growing cell tip and lysosomes in metastatic OMM. In the cis-regulation analysis, we observed metastasis-associated gene, PLEKHA5, the cis gene of lnc-AEBP2-1_1 and lnc-AEBP2-2_1, and microphthalmia-associated transcription factor (MITF), the cis gene of SAMMSON_3, SAMMSON_5 and lnc-MITF-5_1. In the trans-regulation analysis, CTBP2 and SUZ12 regulated lncRNA expression in the core TF-lncRNA-gene network.

CONCLUSION

Our results suggest that lncRNAs may be involved in the metastasis of OMM, and further investigation is needed to focus on the biological functions and the underlining molecular mechanisms exerted by these dysregulated lncRNAs in OMM.

Oral mucosal melanoma treated with carbon ion radiotherapy: a case report

BACKGROUND

Oral mucosal melanoma is a rare disease with a relatively poor prognosis. Carbon ion radiotherapy has been shown to be effective against radiotherapy-resistant tumors owing to its excellent dose concentration and high biological effect.

CASE PRESENTATION

Our patient was a 66-year-old Japanese man with oral mucosal melanoma of his right maxillary gingiva (T4aN0M0). He received carbon ion radiotherapy at 57.6 Gy (relative biological effectiveness) in 16 fractions for 4 weeks. Concomitant chemotherapy (dacarbazine + nimustine + vincristine) was administered at the same time as carbon ion radiotherapy initiation. Two courses of adjuvant chemotherapy were given after carbon ion radiotherapy. Although he experienced grade 2 acute oral mucositis, his symptoms improved within a few weeks of undergoing carbon ion radiotherapy. He was alive at the time of reporting, 35 months after treatment, without any recurrence. Late toxicity has not been observed.

CONCLUSIONS

Carbon ion radiotherapy for oral mucosal melanoma resulted in a good local effect.