Analysis of KIT expression and gene mutation in human acral melanoma: with a comparison between primary tumors and corresponding metastases/recurrences

Treatment of acral and mucosal melanoma: Current and emerging targeted therapies

Targeted therapies revolutionized the management of patients with advanced and metastatic cutaneous melanoma. However, despite recent advances in the understanding of the molecular drivers of melanoma and its treatment with targeted therapies, patients with rare and aggressive melanoma subtypes, including acral melanoma (AM) and mucosal melanomas (MM), show limited long-term clinical benefit from current targeted therapies. While patients with AM or MM and BRAF or KIT mutations may benefit from targeted therapies, the frequency of these mutations is relatively low, and there are no genotype-specific treatments for most patients with AM or MM who lack common driver mutations. The poor prognosis of AM and MM can also be attributed to the lack of understanding of their unique molecular landscapes and clinical characteristics, due to being under-represented in preclinical and clinical studies. We review current knowledge of the molecular landscapes of AM and MM, focusing on actionable therapeutic targets and pathways for molecular targeted therapies, to guide the development of more effective targeted therapies for these cancers. Current and emerging strategies for the treatment of these melanoma subtypes using targeted therapies are also summarized.

Differences in the Clinical and Molecular Profiles of Subungual Melanoma and Acral Melanoma in Asian Patients

Subungual melanoma (SUM) is a rare type of malignant melanoma that arises beneath the nails. SUM is categorized as a type of acral melanoma (AM), which occurs on the hands and feet. SUM is an aggressive type of cutaneous melanoma that is most common among Asian patients. Recent studies reveal that SUM and AM might have different molecular characteristics. Treatment of melanoma relies on analysis of both clinical and molecular data. Therefore, the clinical and molecular characteristics of SUM need to be established, especially during metastasis. To define the mutation profiles of SUM and compare them with those of AM, we performed next-generation sequencing of primary and metastatic tumors of SUM and AM patients. Subungual location was a better independent prognostic factor than acral location for better overall survival (p = 0.001). Patients with SUM most commonly had the triple wild-type (75%) driven by GNAQ (58%) and KIT (25%) mutations, whereas patients with AM had BRAF (28.6%) and RAF (14.3%) molecular types of mutations. Single-nucleotide variations (SNVs) were more common in SUM than in AM, whereas copy number alterations (CNAs) were more common metastatic lesions of AM. Metastatic tumors in patients with SUM and AM showed increases in CNAs (43% and 80%, respectively), but not in SNVs. The number of CNAs increased during metastasis. When compared with AM, SUM has distinct clinical and molecular characteristics.

Nail Apparatus Melanoma: Current Management and Future Perspectives

Nail apparatus melanoma (NAM) is a rare type of cutaneous melanoma that belongs to the acral melanoma subtype. NAM is managed principally in accordance with the general treatment for cutaneous melanoma, but there is scarce evidence in support of this in the literature. Acral melanoma is genetically different from non-acral cutaneous melanoma, while recently accumulated data suggest that NAM also has a different genetic background from acral melanoma. In this review, we focus on recent advances in the management of NAM. Localized NAM should be surgically removed; amputation of the digit and digit-preserving surgery have been reported. Sentinel lymph node biopsy can be considered for invasive NAM for the purpose of accurate staging. However, it is yet to be clarified whether patients with metastatic sentinel lymph nodes can be safely spared completion lymph node dissection. Similar to cutaneous melanoma, immune checkpoint inhibitors and BRAF/MEK inhibitors are used as the first-line treatment for metastatic NAM, but data on the efficacy of these therapies remain scarce. The therapeutic effects of immune checkpoint inhibitors could be lower for NAM than for cutaneous melanoma. This review highlights the urgent need to accumulate data to better define the optimal management of this rare melanoma.

Systematic review and meta-analysis of genomic alterations in acral melanoma

Acral melanoma (AM) tumors arise on the palms, soles, fingers, toes, and nailbeds. A comprehensive systematic meta-analysis of AM genomic aberrations has not been conducted to date. A literature review was carried out to identify studies sequencing AM. Whole-genome/exome data from 181 samples were identified. Targeted panel sequencing data from MSK-IMPACT were included as a validation cohort (n = 92), and studies using targeted hot spot sequencing were also collated for BRAF (n = 26 studies), NRAS (n = 21), and KIT (n = 32). Statistical analysis indicated BRAF, NRAS, PTEN, TYRP1, and KIT as significantly mutated genes. Frequent copy-number aberrations were also found for important cancer genes, such as CDKN2A, KIT, MDM2, CCND1, CDK4, and PAK1, among others. Mapping genomic alterations within the context of the hallmarks of cancer identified four components frequently altered, including (i) sustained proliferative signaling and (ii) evading growth suppression, (iii) genome instability and mutation, and (iv) enabling replicative immortality. This analysis provides the largest analysis of genomic aberrations in AM in the literature to date and highlights pathways that may be therapeutically targetable.

Genomic and Transcriptomic Underpinnings of Melanoma Genesis, Progression, and Metastasis

Melanoma is a deadly skin cancer with rapidly increasing incidence worldwide. The discovery of the genetic drivers of melanomagenesis in the last decade has led the World Health Organization to reclassify melanoma subtypes by their molecular pathways rather than traditional clinical and histopathologic features. Despite this significant advance, the genomic and transcriptomic drivers of metastatic progression are less well characterized. This review describes the known molecular pathways of cutaneous and uveal melanoma progression, highlights recently identified pathways and mediators of metastasis, and touches on the influence of the tumor microenvironment on metastatic progression and treatment resistance. While targeted therapies and immune checkpoint blockade have significantly aided in the treatment of advanced disease, acquired drug resistance remains an unfortunately common problem, and there is still a great need to identify potential prognostic markers and novel therapeutic targets to aid in such cases.

Distribution and clinical role of KIT gene mutations in melanoma according to subtype: a study of 492 Spanish patients

BACKGROUND

KIT mutations are primarily associated with acral and mucosal melanoma, and have been reported to show higher prevalence in chronic sun-damaged (CSD) than non-CSD melanomas.

OBJECTIVES

To investigate the prevalence of KIT mutations in melanoma according to subtype, and determine the clinical role of such mutations.

MATERIALS & METHODS

We present results from a study of a Spanish population of 492 melanomas, classified according to the latest World Health Organization (WHO) guidelines. We analysed the mutational status of KIT and correlated with different clinical variables related to sun exposure and family history.

RESULTS

KIT mutations were significantly more frequent in acral (3/36; 8.3%) and mucosal (4/8; 50%) melanomas than non-acral cutaneous melanomas. No significant difference was observed in KIT mutational status between CSD and non-CSD melanomas.

CONCLUSION

Our results suggest that KIT mutations in melanoma tumours are unrelated to the development of nevi or chronic sun damage, but their presence is associated with aggressive melanomas which show ulceration, vascular invasiveness, and increased Breslow thickness. These findings are consistent with those reported by The Cancer Genome Atlas network.

More than just acral melanoma: the controversies of defining the disease

Acral melanoma (AM) is a malignant cutaneous melanocytic tumour specifically located on the palms, soles, and nail apparatus, which are areas of glabrous (hairless) skin. Acral lentiginous melanoma, a subtype of AM, represents a histopathological subtype diagnosis of cutaneous melanoma with unique morphological and structural features. Despite clear definitions, the misuse of these terms and the inconsistency in reporting the histopathological features of AM cases have become a major obstacle to the study of the disease. In this review, we discuss the epidemiology, histopathological features, prognosis, and genetic profile of AM, highlighting the differences observed when histopathological subtypes are considered. The increasing global effort to characterise AM cases from ethnically diverse populations would benefit greatly from a more consistent classification of the disease.

Tislelizumab in Chinese patients with advanced solid tumors: an open-label, non-comparative, phase 1/2 study

BACKGROUND

Tislelizumab is an investigational, humanized, IgG4 monoclonal antibody with high affinity and binding specificity for programmed cell death-1 (PD-1) that was engineered to minimize binding to FcγR on macrophages in order to abrogate antibody-dependent phagocytosis, a mechanism of T-cell clearance and potential resistance to anti-PD-1 therapy.

METHODS

The purpose of this phase 1/2, open-label, non-comparative study was to examine the safety, tolerability, and antitumor activity of tislelizumab in adult (≥18 years) Chinese patients with histologically or cytologically confirmed advanced solid tumors with measurable disease. The phase 1 portion of the study consisted of a dose-verification study and a pharmacokinetic (PK) substudy; phase 2 was an indication-expansion study including 11 solid tumor cohorts. Patients previously treated with therapies targeting PD-1 or its ligand, programmed cell death ligand-1 were excluded. During dose-verification, dose-limiting toxicities (DLTs) were monitored; safety and tolerability were examined and the previously determined recommended phase 2 dose (RP2D) was verified. The primary endpoint of phase 2 was investigator-assessed objective response rate per Response Evaluation Criteria in Solid Tumors V.1.1.

RESULTS

As of December 1, 2018, 300 patients were treated with tislelizumab 200 mg intravenously once every 3 weeks (Q3W). Median duration of follow-up was 8.1 months (range 0.2-21.9). No DLTs were reported during the phase 1 dose-verification study and the RP2D was confirmed to be 200 mg intravenously Q3W. Most treatment-related adverse events (62%) were grade 1 or 2, with the most common being anemia (n=70; 23%) and increased aspartate aminotransferase (n=67; 22%). Of the 251 efficacy evaluable patients, 45 (18%) achieved a confirmed clinical response, including one patient from the PK substudy who achieved a complete response. Median duration of response was not reached for all except the nasopharyngeal carcinoma cohort (8.3 months). Antitumor responses were observed in multiple tumor types.

CONCLUSIONS

Tislelizumab was generally well tolerated among Chinese patients. Antitumor activity was observed in patients with multiple solid tumors.

TRIAL REGISTRATION NUMBER

CTR20160872.

Frequency of mutations in BRAF, NRAS, and KIT in different populations and histological subtypes of melanoma: a systemic review

Supplemental Digital Content is available in the text.

The presence of mutations of BRAF, NRAS, and KIT genes is recognized as playing a role during carcinogenesis. Our study aims to evaluate and review other studies that present the frequency of mutations of BRAF, NRAS, and KIT genes for different populations, and analyse correlation to their clinical-pathological characteristics and to the demographics of melanoma. Thirty-two articles were selected from a collection of published literature studying 6299 patients. The parameters for correlation to different variables were calculated by odds ratio, for random and single effects. 38.5% of patients present BRAF gene mutations, 16.4% in NRAS, and 10% in KIT. Mutations of the BRAF gene were correlated to superficial spreading melanoma (odds ratio = 1.31), localization in the torso (odds ratio = 1.42) and presence of metastases. Mutations in NRAS were correlated to nodular melanoma (odds ratio = 1.57), localized in the limbs (odds ratio = 1.31). Mutations of the KIT gene were correlated to mucosal melanoma (odds ratio = 1.59). Populations in Brazil, the US, Sweden, Italian, and Australia were found to be correlated to mutations of BRAF and melanoma. Populations in Italy, Sweden, Spain, and the US were found to be correlated to mutations of NRAS. Populations in Japan, China, Turkey, Canada, and Russia were found to be correlated to mutations of KIT. Data correlated to the presence of melanoma and population type is due to the amount of studies performed across of globe.

The tumor genetics of acral melanoma: What should a dermatologist know?

Dermatologists stand at the gateway of individualization of classification, treatment, and outcomes of acral melanoma patients. The acral melanoma genetic landscape differs in vital ways from that of other cutaneous melanomas. These differences have important implications in understanding pathogenesis, treatment, and prognosis. The selection of molecularly targeted therapy must be adapted for acral melanoma. It is also critical to recognize that tumor development is far more complex than an isolated event, reliably treated by a medication acting on a single target. Tumors exhibit intratumor genetic heterogeneity, metastasis may have different genetic or epigenetic features than primary tumors, and tumor resistance may develop because of the activation of alternative genetic pathways. Microenvironmental, immune, and epigenetic events contribute and sustain tumors in complex ways. Treatment strategies with multiple targets are required to effectively disrupt the tumor ecosystem. This review attempts to translate the current molecular understanding of acral melanoma into digestible concepts relevant to the practice of dermatology. The focus is tumor genetics defining potentially treatable cancer pathways, contextualized within the relevant pathologic and molecular features.

Bioinformatic analysis reveals hub genes and pathways that promote melanoma metastasis

BACKGROUND

Melanoma has the highest mortality rate of all skin tumors, and metastases are the major cause of death from it. The molecular mechanism leading to melanoma metastasis is currently unclear.

METHODS

With the goal of revealing the underlying mechanism, three data sets with accession numbers GSE8401, GSE46517 and GSE7956 were downloaded from the Gene Expression Omnibus (GEO) database. After identifying the differentially expressed gene (DEG) of primary melanoma and metastatic melanoma, three kinds of analyses were performed, namely functional annotation, protein-protein interaction (PPI) network and module construction, and co-expression and drug-gene interaction prediction analysis.

RESULTS

A total of 41 up-regulated genes and 79 down-regulated genes was selected for subsequent analyses. Results of pathway enrichment analysis showed that extracellular matrix organization and proteoglycans in cancer are closely related to melanoma metastasis. In addition, seven pivotal genes were identified from PPI network, including CXCL8, THBS1, COL3A1, TIMP3, KIT, DCN, and IGFBP5, which have all been verified in the TCGA database and clinical specimens, but only CXCL8, THBS1 and KIT had significant differences in expression.

CONCLUSIONS

To conclude, CXCL8, THBS1 and KIT may be the hub genes in the metastasis of melanoma and thus may be regarded as therapeutic targets in the future.

The clinical significance of KIT mutations in melanoma: a meta-analysis

This study aimed to evaluate the association of KIT mutations with clinicopathologic features of melanomas using a meta-analysis and to identify differences between Asian and White populations using subgroup analyses. We selected 32 studies from the literature including 5224 patients. The pooled data were combined, and odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Heterogeneity and publication bias were also determined. KIT mutations were reported in 497 (9.5%) of 5224 patients with melanomas, and were associated significantly with age, clinical melanoma subtype, anatomic location, and chronic sun-damage (CSD), but not with sex, histological type, Breslow thickness, ulceration, mitotic rate, or tumor stage. The incidence of KIT mutation was significantly higher in older individuals (OR=1.296, 95% CI: 1.025-1.641; P=0.031), and showed a positive association with mucosal melanoma (OR=1.363, 95% CI: 1.094-1.697; P=0.006), acral melanoma (OR=1.374, 95% CI: 1.123-1.682; P=0.02), and CSD (OR=1.880, 95% CI: 1.127-3.136; P=0.016), but a negative relationship with melanomas arising in non-CSD skin (OR=0.562, 95% CI: 0.392-0.805; P=0.002). The frequency of KIT mutations was associated negatively with melanomas located on the extremities. KIT mutations, which are critical in the genetic pathogenesis of melanomas, define a unique subtype of melanoma associated closely with older age, and acral, mucosal, or CSD sites, but not associated with any histological features or tumor stage. Although the KIT mutation rate is higher in White than Asian populations, no significant difference in clinical association with KIT mutations was detected between the two groups.

KIT mutations and CD117 overexpression are markers of better progression-free survival in vulvar melanomas

BACKGROUND

Few studies have addressed prognostic markers and none has correlated molecular status and prognosis in vulvar melanomas.

OBJECTIVES

To evaluate the clinicopathological features of 95 cases of vulvar melanoma.

METHODS

p53, CD117, Ki-67, neurofibromin, brafv600e and nrasq61r immunostains, and molecular analyses by either targeted next-generation or direct sequencing, were performed on available archival materials.

RESULTS

Molecular testing detected mutations in KIT (44%), BRAF (25%), NF1 (22%), TP53 (17%), NRAS (9%) and TERT promoter (9%). Co-mutation of KIT and NF1 and of KIT and NRAS were identified in two and one cases, respectively. KIT mutations were significantly associated with better progression-free survival in univariate analyses. In multivariate analyses CD117 expression was significantly associated with better progression-free survival. Tumour thickness was significantly associated with worse progression-free and overall survival, and perineural invasion significantly correlated with reduced melanoma-specific survival and reduced overall survival. Cases were from multiple centres and only a subset of samples was available for molecular testing.

CONCLUSIONS

KIT mutations and CD117 overexpression are markers of better progression-free survival. In addition to its prognostic value, molecular testing may identify cases that might respond to targeted agents or immunotherapeutic approaches.

Acral Melanoma in Chinese: A Clinicopathological and Prognostic Study of 142 cases

Acral melanoma (AM), as a peculiar subgroup of melanoma, is rare in Caucasians but has higher incidence in Asians. Large series of study on AM with clinicopathological features and prognostic factors is still limited, especially in Asian population. We retrospectively collected clinical, pathological and follow-up data of 142 AM cases. All patients were Chinese, with the age ranging from 24 to 87 years (mean 62.0; median 62.0). The Breslow thickness of primary lesions ranged from 0.6 to 16.3 mm (mean 4.9; median 3.7). 85.9% of the patients had acral lentiginous histologic subtype. Plantar was the most frequently involved site, followed by heels. Statistically, duration of the lesion before diagnosis (≤2.5 years), Breslow thickness >4.0 mm (T4), high mitotic index (>15 mm⁻²), presence of vascular invasion, regional lymph node metastasis at diagnosis and pathologic stage (II/III/IV) were found to be independent prognostic factors in both univariate and multivariate analyses. The prognosis of AM in Chinese is extremely poor. Our 5- and 10-year disease-specific survival (DSS) rates were 53.3% and 27.4%, respectively. Therefore, AM in Asians represents a more biologically aggressive melanoma subtype and is thought to carry a worse prognosis when compared with other races or cutaneous melanomas in other anatomic sites.

[Immunohistochemical hormonal mismatch and human epidermal growth factor type 2 [HER2] phenotype of brain metastases in breast cancer carcinoma compared to primary tumors]

INTRODUCTION

Phenotype changes between primary tumor and the corresponding brain metastases are recent reported data. Breast cancer, with biological markers predicting prognosis and guiding therapeutic strategy remains an interesting model to observe and evaluate theses changes. The objective of our study was to compare molecular features (estrogen receptor [ER], progesterone receptor [PR], and human epidermal growth factor receptor type 2, [HER2]) between brain metastases and its primary tumor in patients presenting with pathologically confirmed breast cancer.

MATERIAL AND METHODS

This retrospective study was based on the immunohistochemical analysis of the brain metastases paraffin embedded samples stored in our institutional tumor bank, after surgical resection. The level of expression of hormonal receptors and HER2 on brain metastases were centrally reviewed and compared to the expression status in primary breast cancer from medical records.

RESULTS

Forty-four samples of brain metastases were available for analysis. Hormonal receptor modification status was observed in 11/44 brain metastases (25%) for ER and 6/44 (13.6%) for PR. A modification of HER2 overexpression was observed in brain metastases in 6/44 (13.6%). Molecular subtype modification was shown in 17 cases (38.6%). A significant difference was demonstrated between time to develop brain metastases in cases without status modification (HER2, ER and PR) (med=49.5months [7.8-236.4]) and in cases in which brain metastases status differs from primary tumor (med=27.5months [0-197.3]), (P=0.0244, IC95=3.09-51.62, Mann and Whitney test).

CONCLUSION

the main interest of this study was to focus on the molecular feature changes between primary tumor and their brain metastases. Time to develop brain metastases was correlated to phenotypic changes in brain metastases.

Concordance of c-kit mutational status in matched primary and metastatic cutaneous canine mast cell tumors at baseline

Background

Mutation analysis of proto‐oncogene c‐kit (c‐kit) is advisable before starting treatment with tyrosine kinase inhibitors in dogs with mast cell tumor (MCT), including those with metastatic disease. Testing is usually performed on primary tumors, assuming that c‐kit mutation status does not change in metastasis.

Hypothesis/Objectives

To give an insight into the mutational processes and to make a recommendation on the use of c‐kit mutational analysis in the clinical setting.

Animals

Twenty‐one client‐owned dogs with metastatic MCT.

Methods

Dogs undergoing resection or biopsy for both primary and matched metastatic MCT were prospectively enrolled. Total RNA or DNA was extracted from primary MCT and corresponding metastases. Exons 8, 9, and 11 were amplified by PCR and sequenced. Genetic features between primary MCT and metastases were compared. Their correlation with clinicopathologic features was investigated.

Results

Concordance (mutated or wild‐type) of mutational status, evaluable in 21 primary and matched metastatic (20 nodal and 1 splenic) MCTs, was 100%. Three new c‐kit mutations were identified. No significant correlation was detected between c‐kit mutation and clinicopathologic features.

Conclusions and Clinical Importance

Proto‐oncogene c‐kit mutational status is conserved between any primary and its matched secondary tumor, suggesting that both can be used for c‐kit mutational testing. Targeted therapies might be also used to treat metastatic disease.