KIT, NRAS, and BRAF mutations in nail apparatus melanoma

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.

Inhibition of spindle and kinetochore associated complex subunit 3 suppresses the proliferation and invasion and induced the apoptosis of cutaneous melanoma by affecting the PI3K/Akt pathway

Spindle and kinetochore-associated complex subunit 3 (SKA3) is reportedly a key contributor to the progression of various cancers. The present work aimed to evaluate the possible role of SKA3 in cutaneous melanoma (CM). A high SKA3 level was found in CM tissues and predicted a poor prognosis. SKA3 silencing markedly repressed the proliferation, invasion, and epithelial-mesenchymal transition and induced the apoptosis of CM cells. SKA3 silencing decreased the phosphorylation of PI3K and Akt. Akt inhibition markedly reversed SKA3 overexpression-induced oncogenic effects on CM cells. SKA3 silencing significantly prohibited the formation and growth of CM-derived xenograft tumors in nude mice in vivo. Our findings demonstrated SKA3 inhibition repressed the progression of CM by downregulating the PI3K/Akt pathway. This study indicates that SKA3 has potential as an anticancer candidate for CM.

Acral lentiginous melanoma: Clinicopathologic and survival differences according to tumour location

BACKGROUND/OBJECTIVES

Acral lentiginous melanoma (ALM) is a melanoma subtype associated with atypical locations on the hands and feet and advanced disease at diagnosis. There is a limited understanding of whether the survival is similar for nail, non-nail, lower limb and upper limb ALM patients. We therefore explored clinicopathologic characteristics and melanoma-specific survival of ALM patients according to tumour location.

METHODS

A prospectively collected cohort study was performed of all primary invasive cutaneous acral lentiginous melanomas with known thickness and tumour location reviewed at a tertiary referral centre over 21 years.

RESULTS

A total of 101 ALM patients were reviewed from 1994 until 2016. The majority of cases (82/101) occurred on the feet. Hand ALMs were thicker and more likely to be ulcerated than feet ALMs (P = 0.05 and 0.02, respectively); however, survival was not statistically different between these two groups (univariate HR 0.48 P = 0.11, 95% CI, 0.20-1.17; multivariate HR 0.67 P = 0.40, 95% CI, 0.27-1.69, respectively). Non-nail ALM patients had longer survival when compared to nail ALM on univariate analysis (HR 0.40, 95% CI, 0.17 to 0.90) which was accounted for by Breslow thickness and ulceration (multivariate HR 0.56, 95% CI, 0.24 to 1.34).

CONCLUSIONS

The reduced melanoma-specific survival in nail ALM patients was likely due to their greater thickness and ulceration. Although hand ALMs are thicker and more frequently ulcerated, this is likely due to the higher proportion of nail ALMs present in this location.

The molecular basis for immune dysregulation by the hyperactivated E62K mutant of the GTPase RAC2

The RAS-related C3 botulinum toxin substrate 2 (RAC2) is a member of the RHO subclass of RAS superfamily GTPases required for proper immune function. An activating mutation in a key switch II region of RAC2 (RAC2E62K) involved in recognizing modulatory factors and effectors has been identified in patients with common variable immune deficiency. To better understand how the mutation dysregulates RAC2 function, we evaluated the structure and stability, guanine nucleotide exchange factor (GEF) and GTPase-activating protein (GAP) activity, and effector binding of RAC2E62K Our findings indicate the E62K mutation does not alter RAC2 structure or stability. However, it does alter GEF specificity, as RAC2E62K is activated by the DOCK GEF, DOCK2, but not by the Dbl homology GEF, TIAM1, both of which activate the parent protein. Our previous data further showed that the E62K mutation impairs GAP activity for RAC2E62K As this disease mutation is also found in RAS GTPases, we assessed GAP-stimulated GTP hydrolysis for KRAS and observed a similar impairment, suggesting that the mutation plays a conserved role in GAP activation. We also investigated whether the E62K mutation alters effector binding, as activated RAC2 binds effectors to transmit signaling through effector pathways. We find that RAC2E62K retains binding to an NADPH oxidase (NOX2) subunit, p67phox, and to the RAC-binding domain of p21-activated kinase, consistent with our earlier findings. Taken together, our findings indicate that the RAC2E62K mutation promotes immune dysfunction by promoting RAC2 hyperactivation, altering GEF specificity, and impairing GAP function yet retaining key effector interactions.

BRAF, KIT, and NRAS Mutations of Acral Melanoma in White Patients

OBJECTIVES

Malignant acral melanoma (AM) is relatively infrequent in white patients. Molecular investigations have returned variable results regarding the mutational pattern. We sought to describe the mutation profile and clinicopathologic features of AM.

METHODS

We investigated BRAF, KIT, and NRAS mutational status in a series of 31 AM samples from white patients.

RESULTS

Nodular melanoma was the most common histopathologic subtype (48.4%), followed by acral lentiginous melanoma (25.8%) and superficial spreading melanoma (25.8%). BRAF, KIT, and NRAS mutational rates were 12.9%, 17.2%, and 30.0%, respectively. We observed significant associations between KIT mutational status and a thinner Breslow thickness compared with wild-type (WT) status (P = .002), NRAS mutation status and younger age compared with WT. In patients presenting at least one mutation, triple-WT patients presented metastases most frequently.

CONCLUSIONS

Although these data represent preliminary results, better knowledge of tumor biology and prognosis of AM can support the clinical approach and follow-up.