3-O-Methylquercetin from Achyrocline satureioides-cytotoxic activity against A375-derived human melanoma cell lines and its incorporation into cyclodextrins-hydrogels for topical administration

3-O-Methylquercetin (3OMQ), a natural 3-O-methylflavonoid, was isolated from Achyrocline satureioides and purified using the high-performance counter current chromatography (HPCCC) on a semi-preparative scale. High-purity 3OMQ (98%) was obtained with excellent recovery (81.8% (w/w)) and good yield (190 mg/100 g of plant). Isolated 3OMQ was evaluated against the A375 human amelanotic melanoma cancer cell line and A375-derived with different degrees of aggressiveness (A375-A7, A375-G10, and A375-PCDNA3). The results showed that 3OMQ reduced the cell viability of all strains, demonstrating time- and dose-dependent responses. 3OMQ was used to obtain hydrogels for the topical treatment of melanoma. Thus, 3OMQ was incorporated into hypromellose hydrogels with/without different cyclodextrins (CDs). The 3OMQ formulations showed permeation/retention in all skin layers, namely stratum corneum, epidermis, and dermis. A significant amount of 3OMQ was found in the replication site of the melanoma cells (epidermis and dermis). Altogether, these results demonstrate that 3OMQ can be isolated from Achyrocline satureioides by HPCCC on a semi-preparative scale and exhibit cytotoxic activity against melanoma cells. Its incorporation into an HPMC hydrogel containing HP-β-CD yielded a formulation with excellent technological and biopharmaceutical characteristics for evaluating the topical management of melanoma.

Abstract 3438: Genetic analysis of melanoma from an albino patient

Melanoma, the deadliest type of skin cancer, derives from the transformation of melanocytes, which protect the skin from ultraviolet radiation (UVR) through the synthesis of melanin. UVR is the major risk factor for melanoma. Intriguingly, in people with oculocutaneous albinism (OCA), who lack or have a reduction in melanin synthesis melanoma is surprisingly rare, whereas other UVR-driven skin cancers are comparatively high. Since UVR exposure and light skin complexion increase melanoma risk, it is unclear why melanoma is rare in OCA. Therefore, we evaluated how the absence of melanin impact the mutation burden in OCA and identify driver mutations by whole exome sequencing (WES) analysis of melanomas from a patient with OCA.

The patient (in their 50s) presented cutaneous basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) in addition to melanoma. The histopathology of one tumor (sample A), located on the left forearm, indicated a desmoplastic nodular melanoma, Clark level III, Breslow of 1 mm and a high mitotic index. The second tumor (sample B) was located on the right knee and presented a superficial spreading melanoma, Clark level II, a Breslow of 0.31 mm and a low mitotic index. For WES, genomic DNA was purified from formalin-fixed paraffin-embedded tissue sections and compared against germline blood. Analysis confirmed a G47D mutation in the TYR gene, which has previously been reported in OCA1B patients. Consistent with sample A coming from an area habitually exposed to UVR, it presented 4874 SNVs and 1556 missense SNVs and a predominant signature 7 mutational process. Similarly, consistent with sample B coming from an area that is habitually protected, it presented only 45 SNVs and 16 missense SNVs and did not present a predominant signature 7 mutational process. Notably, despite the histopathology of the skin adjacent to sample B appeared normal, it presented 39 SNVs and 10 missense SNVs. Intriguingly, all samples harbor NRASQ61K mutations and sample B additionally presented a mutation in NOTCH1, which is more common in SCC. Thus, we show that in OCA, melanomas from a UVR exposed areas present high mutation burden and UV mutational signature, whereas melanomas from UVR protected skin present a low mutation burden. Our data suggest that NRASQ61K is a driver oncogene in melanomas from albinos and that these patients can develop both UVR-driven and UVR-independent melanomas.

Citation Format: Candelaria Bracalente, Piyushkumar Mundra, Adriana Rinflerch, Pablo Garcia Martinez, Victoria Volonteri, Lucas Trucco, Gaston Galimberti, Nathalie Dhomen, Valeria Pavet Rodriguez, Richard Marais. Genetic analysis of melanoma from an albino patient [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3438.

Cofilin-1 levels and intracellular localization are associated with melanoma prognosis in a cohort of patients

Melanoma is an aggressive cancer with highly metastatic ability. We propose cofilin-1, a key protein in the regulation of actin dynamics and migration, as a prognostic marker. We determined cofilin-1 levels in a retrospective cohort of patients with melanomas and benign lesions of melanocytes (nevi) by immunohistochemistry. Higher cofilin-1 levels were found in malignant melanoma (MM) with Breslow Index (BI)>2 vs MM with BI<2, melanoma in situ (MIS) and nevi and also in MM with metastasis vs MM without detected metastasis. Kaplan-Meier survival curves were performed, clustering patients according to either the type of melanocytic lesions or cofilin-1 level. Survival curves demonstrated worse prognosis of patients with high vs low cofilin-1 levels. TCGA database analysis of melanoma also showed low survival in patients with upregulated cofilin-1 mRNA vs patients without alteration in CFL1 mRNA expression. As cofilin-1 has a dual function depending on its intracellular localization, we evaluated nuclear and cytoplasmic levels of cofilin-1 in melanoma and nevi samples by immunofluorescence. MM with high Breslow index and metastatic cells not only presented cytoplasmic cofilin-1, but also showed this protein at the nucleus. An increase in nuclear/cytoplasmic cofilin-1 mean fluorescence ratio was observed in MM with BI>2 vs MM with BI<2, MIS and nevi. In conclusion, an association of cofilin-1 levels with malignant features and an inverse correlation with survival were demonstrated. Moreover, this study suggests that not only the higher levels of cofilin-1, but also its nuclear localization can be proposed as marker of worse outcome of patients with melanoma.

Galectins: Multitask signaling molecules linking fibroblast, endothelial and immune cell programs in the tumor microenvironment

Tumor cells corrupt surrounding normal cells instructing them to support proliferative, pro-angiogenic and immunosuppressive networks that favor tumorigenesis and metastasis. This dynamic cross-talk is sustained by a range of intracellular signals and extracellular mediators produced by both tumoral and non-tumoral cells. Galectins -whether secreted or intracellularly expressed- play central roles in the tumorigenic process by delivering regulatory signals that contribute to reprogram fibroblasts, endothelial and immune cell programs. Through glycosylation-dependent or independent mechanisms, these endogenous lectins control a variety of cellular events leading to tumor cell proliferation, survival, migration, inflammation, angiogenesis and immune escape. Here we discuss the role of galectin-driven pathways, particularly those activated in non-tumoral stromal cells, in modulating tumor progression.

Reprogramming human A375 amelanotic melanoma cells by catalase overexpression: Reversion or promotion of malignancy by inducing melanogenesis or metastasis

Advanced melanoma is the most aggressive form of skin cancer. It is highly metastatic and dysfunctional in melanogenesis; two processes that are induced by H₂O₂. This work presents a melanoma cell model with low levels of H₂O₂ induced by catalase overexpression to study differentiation/dedifferentiation processes. Three clones (A7, C10 and G10) of human A375 amelanotic melanoma cells with quite distinct phenotypes were obtained. These clones faced H₂O₂ scavenging by two main strategies. One developed by clone G10 where ROS increased. This resulted in G10 migration and metastasis associated with the increased of cofilin-1 and CAP1. The other strategy was observed in clone A7 and C10, where ROS levels were maintained reversing malignant features. Particularly, C10 was not tumorigenic, while A7 reversed the amelanotic phenotype by increasing melanin content and melanocytic differentiation markers. These clones allowed the study of potential differentiation and migration markers and its association with ROS levels in vitro and in vivo, providing a new melanoma model with different degree of malignancy.

Reprogramming human A375 amelanotic melanoma cells by catalase overexpression: Upregulation of antioxidant genes correlates with regression of melanoma malignancy and with malignant progression when downregulated

Reactive oxygen species (ROS) are implicated in tumor transformation. The antioxidant system (AOS) protects cells from ROS damage. However, it is also hijacked by cancers cells to proliferate within the tumor. Thus, identifying proteins altered by redox imbalance in cancer cells is an attractive prognostic and therapeutic tool. Gene expression microarrays in A375 melanoma cells with different ROS levels after overexpressing catalase were performed. Dissimilar phenotypes by differential compensation to hydrogen peroxide scavenging were generated. The melanotic A375-A7 (A7) upregulated TYRP1, CNTN1 and UCHL1 promoting melanogenesis. The metastatic A375-G10 (G10) downregulated MTSS1 and TIAM1, proteins absent in metastasis. Moreover, differential coexpression of AOS genes (EPHX2, GSTM3, MGST1, MSRA, TXNRD3, MGST3 and GSR) was found in A7 and G10. Their increase in A7 improved its AOS ability and therefore, oxidative stress response, resembling less aggressive tumor cells. Meanwhile, their decrease in G10 revealed a disruption in the AOS and therefore, enhanced its metastatic capacity.

These gene signatures, not only bring new insights into the physiopathology of melanoma, but also could be relevant in clinical prognostic to classify between non aggressive and metastatic melanomas.

Abstract 1561: Gene expression analysis identifies heterogeneity in cutaneous melanoma subjects with disruptive MC1R alleles and BRAF hotspot mutations

Background: Previous epidemiological and population sequencing studies have established that subjects with melanocortin 1 receptor (MC1R) germline mutations, associated with red hair and light skin phenotypes, have an increased risk of melanoma. However, several conflicting reports about the role of BRAF somatic mutations in MC1R subjects exist in the literature. We hypothesise that this conflict is due to biological process driven heterogeneity within MC1R subjects carrying disruptive alleles. To understand the heterogeneity, we analysed the TCGA cohort at the gene expression level using mRNA sequencing data.

Method: From the previously published studies, we identified 68 cutaneous melanoma subjects who were of white ethinicity, had at least one disruptive allele of MC1R, and had BRAF mutations. Associated clinical and mRNA sequencing data were downloaded from the Firebrowse website. An unbiased hierarchical clustering analysis was performed using the preprocessed mRNA data containing 14669 gene expressions. The resultant clusters were then characterised using available clinical variables. A differential expression analysis was performed to identify the genomic signatures of these clusters. The resultant p-values were corrected for false discovery rate (FDR) using the Benjamini-Hochberg approach. Genes with corrected p-values less than 0.01 were further analysed using gene set enrichment analysis (GSEA) preranked lists.

Results: An unbiased clustering identified two clear and separable clusters with 40 and 28 subjects respectively. The UV-signature (dipyrimidine C&gt;T load) was correlated with these clusters (p-value = 0.047). However, no significant differences in age at the time of diagnosis, overall survival, and total mutation load between clusters were observed. At the genomic level, 2588 genes were significantly differentially expressed between two clusters (FDR corrected p- value less than 0.05). The top 10 differentially expressed genes included ATF2, MSH6, SP3, MAP3K2, and VEGFB. Further GSEA revealed gene sets playing roles in several pathways and biological processes, including oxidative phosphorylation, UV response in keratinocytes, DNA repair, cell cycle, and cellular response to stress.

Conclusion: Cutaneous melanoma subjects with disruptive MC1R alleles and BRAF hotspot mutations have heterogeneous gene expression profiles with several key oncogenes differentially expressed. This suggests potential roles of other pathways, either independently or in cooperation with BRAF mutations, in melanomagenesis in MC1R bearing patients.

Citation Format: Piyushkumar A. Mundra, Candelaria Bracalente, Lucas Trucco, Nathalie Dhomen, Richard Marais. Gene expression analysis identifies heterogeneity in cutaneous melanoma subjects with disruptive MC1R alleles and BRAF hotspot mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1561. doi:10.1158/1538-7445.AM2017-1561

Glycosylation-dependent binding of galectin-8 to activated leukocyte cell adhesion molecule (ALCAM/CD166) promotes its surface segregation on breast cancer cells

BACKGROUND

We previously demonstrated that the activated leukocyte cell adhesion molecule (ALCAM/CD166) can interact with galectin-8 (Gal-8) in endothelial cells. ALCAM is a member of the immunoglobulin superfamily that promotes homophilic and heterophilic cell-cell interactions. Gal-8 is a "tandem-repeat"-type galectin, known as a matricellular protein involved in cell adhesion. Here, we analyzed the physical interaction between both molecules in breast cancer cells and the functional relevance of this phenomenon.

METHODS

We performed binding assays by surface plasmon resonance to study the interaction between Gal-8 and the recombinant glycosylated ALCAM ectodomain or endogenous ALCAM from MDA-MB-231 breast cancer cells. We also analyzed the binding of ALCAM-silenced or control breast cancer cells to immobilized Gal-8 by SPR. In internalization assays, we evaluated the influence of Gal-8 on ALCAM surface localization.

RESULTS

We showed that recombinant glycosylated ALCAM and endogenous ALCAM from breast carcinoma cells physically interacted with Gal-8 in a glycosylation-dependent fashion displaying a differential behavior compared to non-glycosylated ALCAM. Moreover, ALCAM-silenced breast cancer cells exhibited reduced binding to Gal-8 relative to control cells. Importantly, exogenously added Gal-8 provoked ALCAM segregation, probably trapping this adhesion molecule at the surface of breast cancer cells.

CONCLUSIONS

Our data indicate that Gal-8 interacts with ALCAM at the surface of breast cancer cells through glycosylation-dependent mechanisms.

GENERAL SIGNIFICANCE

A novel heterophilic interaction between ALCAM and Gal-8 is demonstrated here, suggesting its physiologic relevance in the biology of breast cancer cells.

Induction and persistence of large γH2AX foci by high linear energy transfer radiation in DNA-dependent protein kinase-deficient cells

PURPOSE

To evaluate the cell response to DNA double-strand breaks induced by low and high linear energy transfer (LET) radiations when the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), an essential protein of the nonhomologous end-joining repair pathway, lacks kinase activity.

METHODS AND MATERIALS

CHO10B2, a Chinese hamster ovary cell line, and its derived radiosensitive mutant cell line, irs-20, lacking DNA-PKcs activity, were evaluated after 0 to 3 Gy of γ-rays, plateau and Bragg peak protons, and lithium beams by clonogenic assay, and as a measurement of double-strand breaks, phosphorylated H2AX (γH2AX) foci number and size were quantified by immunocytofluorescence.

RESULTS

Irs-20 exhibited greater radiosensitivity and a higher amount of γH2AX foci than CHO10B2 at 6 hours after irradiation for all types of radiations. Remarkably, CHO10B2 and irs-20 maintained their difference in radiosensitivity after high-LET radiation. Six hours after low-LET radiations, irs-20 did not reach basal levels of γH2AX at high doses, whereas CHO10B2 recovered basal levels for all doses. After high-LET radiation, only CHO10B2 exhibited a reduction in γH2AX foci, but it never reached basal levels. Persistent foci in irs-20 confirmed a repair deficiency. Interestingly, after 30 minutes of high-LET radiation both cell lines exhibited large foci (size>0.9 μm2) related to the damage nature, whereas at 6 hours irs-20 showed a higher amount of large foci than CHO10B2, with a 7-fold increase at 3 Gy, that could also be associated to radiosensitivity.

CONCLUSIONS

We demonstrated, for the first time, an association between deficient DNA-PKcs activity and not only high levels of H2AX phosphorylation but also persistence and size increase of γH2AX foci after high-LET irradiation.