Increased Non-Homologous End Joining Makes DNA-PK a Promising Target for Therapeutic Intervention in Uveal Melanoma.

Uveal melanoma (UM) is the most common primary intraocular tumour in adults, with a mean survival of six months following metastasis. The survival rates have not improved in over 30 years. This study has shown that sister chromatid exchange (SCE) is low in UM which is likely due to a reduced expression of FANCD2. As FANCD2 can function to suppress non-homologous end joining (NHEJ), this study therefore investigated NHEJ in UM. The activation of the catalytic subunit of the NHEJ pathway protein DNA-dependent protein kinase (DNA-PK) was measured by analysing the foci formation and the ligation efficiency by NHEJ determined using a plasmid-based end-joining assay. Using small-interfering RNA (siRNA) knock-down, and chemical inhibitors of DNA-PK, the survival of primary UM cultures and two cell lines were determined. To assess the homologous recombination capacity in response to the inhibition of DNA-PK, a SCE analysis was performed. In addition, to support the findings, the messenger RNA (mRNA) expression of genes associated with NHEJ was analysed using the Cancer Genome Atlas (TCGA)-UM RNAseq data (n = 79). The NHEJ activity and DNA-PKcs activation was upregulated in UM and the inhibition of DNA-PK selectively induced apoptosis and sensitized to ionising radiation and inter-strand cross-linking agents. The inhibition of the NHEJ protein DNA-PK is lethal to UM, indicating a potentially effective therapeutic option, either alone or as a sensitizer for other treatments.

Genetic Profiling of Primary Orbital Melanoma: An Analysis of 6 Cases with Clinicopathologic Correlation.

PURPOSE: To analyze the genetic profile of 6 cases of primary orbital melanoma with clinicopathologic correlation. DESIGN: Retrospective noninterventional study to analyze the genetic profile of 6 cases of primary orbital melanoma and to correlate the genetic findings with prognosis and clinicopathologic features. Inclusion criteria were patients with primary orbital melanoma with no evidence of primary eyelid skin, conjunctival, uveal, or remote melanoma at extraocular sites. PARTICIPANTS: The study involved 6 primary orbital melanomas from 6 patients. Four patients were exenterated and 2 had incisional biopsies performed. METHODS: Clinical notes and radiologic records were assessed to ascertain clinical tumor behavior. Sections were stained with hematoxylin-eosin and exposed to immunohistochemistry for S100, MelA, HMB45, Sox10, and BAP1. Melanoma DNA was exposed to array comparative genomic hybridization to assess gross chromosomal copy number changes. Point mutation assessment and Sanger sequencing were performed for GNAQ, GNA11, BRAF, NRAS, pTERT, SF3B1, and EIF1AX. MAIN OUTCOME MEASURES: These were the presence of gross chromosomal copy number changes and the presence of mutations in GNAQ, GNA11, BRAF, NRAS, pTERT, SF3B1, and EIF1AX; the presence of metastases and time period between diagnosis and death from melanoma; and correlation between the tumor genetic profile and the clinical behavior of the tumor. RESULTS: One of the 6 cases was clinically associated with oculodermal melanocytosis. Of the 6 patients, 3 died of melanoma metastases and 1 of unrelated causes; 2 remain alive at last review. Three of the 6 cases were histologically associated with a benign precursor lesion. All melanomas expressed S100, MelA, HMB45, and Sox10. One patient showed loss of BAP1 nuclear staining. The most frequent chromosomal gains across the 6 cases, in order of frequency, were 6p, 8q, 17q, 6q, and 20p. The most frequently lost regions were 1p, 9p, 16q, and 17p. One patient showed monsomy 3 and gain of 8q (and showed the BAP1 loss). Mutations were found in GNAQ (1 case), GNA11 (1 case), SF3B1 (2 cases), NRAS (2 cases), and pTERT (2 cases). CONCLUSIONS: The data point to 2 genetic groups for primary orbital conjunctiva melanoma-like and a uveal melanoma-like group. A larger study would help confirm this suggestion.

Phenotypic Plasticity in Uveal Melanoma Is Not Restricted to a Tumor Subpopulation and Is Unrelated to Cancer Stem Cell Characteristics.

Purpose: Uveal melanoma (UM) is the most common primary intraocular malignancy in adults and approximately half of those diagnosed will die of metastasis. This study investigates whether UM progression is driven by a subpopulation of stem-like cells, termed "cancer stem cells" (CSCs). Methods: Expression of postulated stem cell markers aldehyde dehydrogenase (ALDH), CD44, and CD133 was analyzed in UM cell lines and primary UM short-term cultures (STCs) established from tumor samples. Additionally, the notion of a "cellular hierarchy" within UM was investigated. Finally, the phenomenon of phenotypic plasticity in response to environmental factors was explored. Results: We demonstrate that expression of ALDH, CD44, and CD133 does not select for a subpopulation of stem-like cells in either UM cell lines or UM STCs. Furthermore, there is an absence of a cellular hierarchy in cell lines and all cells in culture are able to drive tumor progression. Last, we show that established UM cell lines and UM STCs are plastic in nature and switch their phenotype in response to environmental stimuli. Conclusions: We hypothesize that this capacity to undergo phenotypic plasticity may be a consequence of neural crest lineage and renders the exploration of the CSC hypothesis extremely challenging in UM.

Late Solitary Extraocular Recurrence From Previously Resected Iris Melanoma.

PURPOSE: To report on cases of late extraocular relapse of previously resected iris melanoma, without concurrent intraocular recurrence. DESIGN: Retrospective case series. METHODS: A retrospective chart review of 4 patients diagnosed with late subconjunctival relapse of previously resected iris melanoma. RESULTS: Three female patients and 1 male patient underwent iris tumor resection and presented to our service with suspicious conjunctival lesions at a median of 22 years later (mean: 21 years). None showed intraocular relapse. Treatment of the conjunctival tumors included excisional biopsy (n = 4), followed by cryotherapy (n = 3) and/or brachytherapy (n = 3). In all cases, histopathology confirmed malignant melanoma, with no intraepithelial component or associated melanosis. Genetic sequencing (n = 3) showed wild-type BRAF and NRAS in all. GNA11 mutation was found in 1 case. On array-based comparative genomic hybridization (n = 3), gain of 6p was found in 2 cases and gain of 8 in 2. Overall, findings were strongly suggestive of a diagnosis of late extraocular relapse from previously resected iris melanoma. In a median of 2.5 years (mean: 7.7 years) from the subconjunctival relapse, no further episodes of intraocular/extraocular recurrence were recorded, and all patients were free from distant metastasis. CONCLUSIONS: Patients undergoing iris melanoma resection are at risk of developing late solitary extraocular relapse even more than 30 years after surgery. In the absence of an intraocular component, diagnosis may be challenging, as tumors mimic a primary conjunctival lesion. Management by excisional biopsy followed by adjuvant therapy was successful, and histopathology and genetic analysis supported a diagnosis of extraocular uveal tumor spread rather than a primary conjunctival tumor.

Photodynamic killing of cancer cells by a Platinum(II) complex with cyclometallating ligand.

Photodynamic therapy that uses photosensitizers which only become toxic upon light-irradiation provides a strong alternative to conventional cancer treatment due to its ability to selectively target tumour material without affecting healthy tissue. Transition metal complexes are highly promising PDT agents due to intense visible light absorption, yet the majority are toxic even without light. This study introduces a small, photostable, charge-neutral platinum-based compound, Pt(II) 2,6-dipyrido-4-methyl-benzenechloride, complex 1, as a photosensitizer, which works under visible light. Activation of the new photosensitizer at low concentrations (0.1-1 µM) by comparatively low dose of 405 nm light (3.6 J cm(-2)) causes significant cell death of cervical, colorectal and bladder cancer cell lines, and, importantly, a cisplatin resistant cell line EJ-R. The photo-index of the complex is 8. We demonstrate that complex 1 induces irreversible DNA single strand breaks following irradiation, and that oxygen is essential for the photoinduced action. Neither light, nor compound alone led to cell death. The key advantages of the new drug include a remarkably fast accumulation time (diffusion-controlled, minutes), and photostability. This study demonstrates a highly promising new agent for photodynamic therapy, and attracts attention to photostable metal complexes as viable alternatives to conventional chemotherapeutics, such as cisplatin.