Cancer cells, including melanoma, often metastasize regionally through lymphatics before metastasizing systemically through the blood 1 – 4 ; however, the reason for this is unclear. Here we show that melanoma cells in lymph experience less oxidative stress and form more metastases than melanoma cells in blood. Immunocompromised mice with patient-derived melanomas and immunocompetent mice with mouse melanomas had more melanoma cells per microliter of tumor-draining lymph than tumor-draining blood. Cells metastasizing through blood, but not lymph, became dependent on the ferroptosis inhibitor GPX4. Cells pre-treated with chemical ferroptosis inhibitors formed more metastases than untreated cells after intravenous, but not intralymphatic, injection. We observed multiple differences between lymph fluid and blood plasma that may contribute to decreased oxidative stress and ferroptosis in lymph, including higher levels of glutathione and oleic acid, and less free iron, in lymph. Oleic acid protected melanoma cells from ferroptosis in an Acsl3 -dependent manner and increased their capacity to form metastatic tumors. Melanoma cells from lymph nodes were more resistant to ferroptosis and formed more metastases after intravenous injection than melanoma cells from subcutaneous tumors. Exposure to the lymphatic environment thus protects melanoma cells from ferroptosis and increases their ability to survive during subsequent metastasis through the blood.

SUMMARY Smoothened (SMO) inhibitors are under clinical investigation for the treatment of several cancers. Vismodegib is approved for the treatment of locally advanced and metastatic basal cell carcinoma (BCC). Most BCC patients experience significant clinical benefit on vismodegib, however, some develop resistance. Genomic analysis of tumor biopsies revealed vismodegib resistance is associated with Hedgehog (Hh) pathway reactivation, predominantly through mutation of the drug target SMO and to a lesser extent through concurrent copy number changes in SUFU and GLI2. SMO mutations either directly impaired drug binding or activated SMO to varying levels. Furthermore, we found evidence for intra-tumor heterogeneity, suggesting that a combination of therapies targeting components at multiple levels of the Hh pathway is required to overcome resistance.

Over the past few years, the NCCN Guidelines for Melanoma: Cutaneous have been expanded to include pathways for treatment of microscopic satellitosis (added in v2.2020), and the following Principles sections: Molecular Testing (added in v2.2019), Systemic Therapy Considerations (added in v2.2020), and Brain Metastases Management (added in v3.2020). The v1.2021 update included additional modifications of these sections and notable revisions to Principles of: Pathology, Surgical Margins for Wide Excision of Primary Melanoma, Sentinel Lymph Node Biopsy, Completion/Therapeutic Lymph Node Dissection, and Radiation Therapy. These NCCN Guidelines Insights discuss the important changes to pathology and surgery recommendations, as well as additions to systemic therapy options for patients with advanced disease.

IMPORTANCE Melanoma arising in chronically photodamaged skin, especially on the head and neck, is often characterized by poorly defined clinical margins and unpredictable occult extension. Staged excision techniques have been described to treat these challenging melanomas.OBJECTIVE To investigate the local recurrence rates and margin to clearance end points using staged excision with comprehensive hematoxylin-eosin-stained permanent section margin control. DESIGN, SETTING, AND PARTICIPANTSIn this observational cohort study performed from October 8, 1997, to December 31, 2006, with a median follow-up of 9.3 years, 806 patients with melanoma on the head and neck, where clinical occult extension is common, were studied at an academic medical center.INTERVENTIONS Staged excision with comprehensive hematoxylin-eosin-stained permanent section margin control commonly known as the square technique. MAIN OUTCOMES AND MEASURESLocal recurrence rates and margin to clearance end points.RESULTS A total of 806 patients (276 women [34.2%]; 805 white [99.9%]) with a median age at the time of first staged excision procedure of 65 years (range, 20-94 years) participated in the study. The estimated local recurrence rates were 1.4% at 5 years, 1.8% at 7.5 years, and 2.2% at 10 years. For each 50-mm 2 increase in the size of the clinical lesion, there was a 9% increase in the rate of local recurrence (hazard ratio, 1.09; 95% CI, 1.02-1.15; P = .02). The mean (SD) margin from lesion to clearance for melanoma in situ was 9.3 (5.1) mm compared with 13.7 (5.9) mm for invasive melanoma. For melanoma in situ, margins were clear after 5 mm or less in 232 excisions (41.1%) and after 10 mm or less in 420 excisions (74.5%). For invasive melanoma, margins were clear after 5 mm or less in 8 excisions (3.0%) and after 10 mm or less in 141 excisions (52.2%). CONCLUSIONS AND RELEVANCEStaged excision with comprehensive permanent section margin control of melanomas arising in chronically sun-damaged skin on the head and neck has favorable recurrence rates when melanoma margins are difficult to assess, and recurrence rates are high with traditional techniques.

ETS transcription factors are commonly deregulated in cancer by chromosomal translocation, overexpression or post-translational modification to induce gene expression programs essential in tumorigenicity. Targeted destruction of these proteins may have therapeutic impact. Here we report that Ets-1 destruction is regulated by the deubiquitinating enzyme, Usp9x, and has major impact on the tumorigenic program of metastatic melanoma. Ets-1 deubiquitination blocks its proteasomal destruction and enhances tumorigenicity, which could be reversed by Usp9x knockdown or inhibition. Usp9x and Ets-1 levels are coincidently elevated in melanoma with highest levels detected in metastatic tumours versus normal skin or benign skin lesions. Notably, Ets-1 is induced by BRAF or MEK kinase inhibition, resulting in increased NRAS expression, which could be blocked by inactivation of Usp9x and therapeutic combination of Usp9x and MEK inhibitor fully suppressed melanoma growth. Thus, Usp9x modulates the Ets-1/NRAS regulatory network and may have biologic and therapeutic implications.