Genetic favouring of pheomelanin‐based pigmentation limits physiological benefits of coloniality in lesser kestrels Falco naumanni

Pheomelanin contributes to the pigmentation phenotype of animals by producing orange and light brown colours in the integument. However, pheomelanin synthesis in melanocytes requires consumption of glutathione (GSH), the most important intracellular antioxidant. Therefore, a genetic control favouring the production of large amounts of pheomelanin for pigmentation may lead to physiological costs under environmental conditions that promote oxidative stress. We investigated this possibility in the context of breeding coloniality, a reproductive strategy that may affect oxidative stress. We found in lesser kestrel Falco naumanni nestlings that the GSH:GSSG ratio, which decreases with systemic oxidative stress, increased with the size of the colony where they were reared, but the expression in feather melanocytes of five genes involved in pheomelanin synthesis (Slc7a11, Slc45a2, CTNS, MC1R and AGRP) did not vary with colony size. The antioxidant capacity (TEAC) of lesser kestrel nestlings also increased with colony size, but in a manner that depended on Slc7a11 expression and not on the expression of the other genes. Thus, antioxidant capacity increased with colony size only in nestlings least expressing Slc7a11, a gene with a known role in mediating cysteine (a constituent amino acid of GSH) consumption for pheomelanin production. The main predictor of the intensity of pheomelanin‐based feather colour was Slc45a2 expression followed in importance by Slc7a11 expression, hence suggesting that the genetic regulation of the pigmentation phenotype mediated by Slc7a11 and a lack of epigenetic lability in this gene limits birds from benefiting from the physiological benefits of coloniality.     

Exposure to a competitive social environment activates an epigenetic mechanism that limits pheomelanin synthesis in zebra finches

Competitive environments promote high testosterone levels, produce oxidative stress and, consequently, impair cellular homeostasis. The regulation of genes involved in the synthesis of the pigment pheomelanin in melanocytes seems to help to maintain homeostasis against environmental oxidative stress. Here, we experimentally increased social interactions in some zebra finch (Taeniopygia guttata) males by keeping them in groups of six birds during feather growth, while others were kept alone, to test if melanocytes show epigenetic lability under a competitive social environment. As these changes may depend on the oxidative status, we administrated buthionine sulfoximine (BSO) to decrease the antioxidant capacity of some birds. The competitive environment downregulated a gene involved in pheomelanin synthesis (Slc7a11) by changing the level of DNA methylation in feather melanocytes. In other genes involved in pheomelanin synthesis (Slc45a2, MC1R and AGRP), DNA methylation was also affected, but no changes in expression were detected. Exposure to the competitive environment did not affect systemic oxidative stress and damage, indicating that a protective epigenetic mechanism that changes the expression of Slc7a11 may have been activated. However, no changes to the pigmentation phenotype of birds were found, probably due to the short duration or low intensity of the competitive environment. BSO treatment did not affect the epigenetic mechanism, suggesting that the antioxidant capacity of birds was high enough to deal with the competitive environment. An epigenetic mechanism limiting pheomelanin synthesis therefore becomes activated under exposure to a competitive environment in male zebra finches, which may help to avoid damage caused by competitive interactions.     

Adaptive downregulation of pheomelanin‐related Slc7a11 gene expression by environmentally induced oxidative stress

Pheomelanin is a sulphur‐containing yellow‐to‐reddish pigment whose synthesis consumes the main intracellular antioxidant (glutathione; GSH) and its precursor cysteine. Cysteine used for pheomelanogenesis cannot be used for antioxidant protection. We tested whether the expression of Slc7a11, the gene regulating the transport of cysteine to melanocytes for pheomelanogenesis, is environmentally influenced when cysteine/GSH are most required for antioxidant protection. We found that zebra finches Taeniopygia guttata developing pheomelanin‐pigmented feathers during a 12‐day exposure to the pro‐oxidant diquat dibromide downregulated the expression of Slc7a11 in feather melanocytes, but not the expression of other genes that affect pheomelanogenesis by mechanisms different from cysteine transport such as MC1R and Slc45a2. Accordingly, diquat‐treated birds did not suffer increased oxidative stress. This indicates that some animals have evolved an adaptive epigenetic lability that avoids damage derived from pheomelanogenesis. This mechanism should be explored in human Slc7a11 to help combat some cancer types related to cysteine consumption.     

Changes in melanocyte RNA and DNA methylation favour pheomelanin synthesis and may avoid systemic oxidative stress after dietary cysteine supplementation in birds

Cysteine plays essential biological roles, but excessive amounts produce cellular oxidative stress. Cysteine metabolism is mainly mediated by the enzymes cysteine dioxygenase and γ‐glutamylcysteine synthetase, respectively coded by the genes CDO1 and GCLC. Here we test a new hypothesis posing that the synthesis of the pigment pheomelanin also contributes to cysteine homeostasis in melanocytes, where cysteine can enter the pheomelanogenesis pathway. We conducted an experiment with the Eurasian nuthatch Sitta europaea, a bird producing large amounts of pheomelanin for feather pigmentation, to investigate if melanocytes show epigenetic lability under exposure to excess cysteine. We increased systemic cysteine levels in nuthatches by supplementing them with dietary cysteine during growth. In feather melanocytes this led to the downregulation of genes involved in intracellular cysteine metabolism (GCLC), cysteine transport to the cytosol from the extracellular medium (Slc7a11) and from melanosomes (CTNS), and regulation of tyrosinase activity (MC1R and ASIP). These changes were mediated by increases in DNA m⁵C in all genes except Slc7a11, which experienced RNA m⁶A depletion. Birds supplemented with cysteine synthesized more pheomelanin than controls, but did not suffer higher systemic oxidative stress. These results suggest that excess cysteine activates an epigenetic mechanism that favours pheomelanin synthesis and may protect against oxidative stress.     

Gyrfalcons <Emphasis Type="Italic">Falco rusticolus</Emphasis> adjust <Emphasis Type="Italic">CTNS</Emphasis> expression to food abundance: a possible contribution to cysteine homeostasis

Melanins form the basis of animal pigmentation. When the sulphurated form of melanin, termed pheomelanin, is synthesized, the sulfhydryl group of cysteine is incorporated to the pigment structure. This may constrain physiological performance because it consumes the most important intracellular antioxidant (i.e., glutathione, GSH), of which cysteine is a constitutive amino acid. However, this may also help avoid excess cysteine, which is toxic. Pheomelanin synthesis is regulated by several genes, some of them exerting this regulation by controlling the transport of cysteine in melanocytes. We investigated the possibility that these genes are epigenetically labile regarding protein intake and thus contribute to cysteine homeostasis. We found in the Icelandic population of gyrfalcon Falco rusticolus, a species that pigments its plumage with pheomelanin, that the expression of a gene regulating the export of cystine out of melanosomes (CTNS) in feather melanocytes of developing nestlings increases with food abundance in the breeding territories where they were reared. The expression of other genes regulating pheomelanin synthesis by different mechanisms of influence on cysteine availability (Slc7a11 and Slc45a2) or by other processes (MC1R and AGRP) was not affected by food abundance. As the gyrfalcon is a strict carnivore and variation in food abundance mainly reflects variation in protein intake, we suggest that epigenetic lability in CTNS has evolved in some species because of its potential benefits contributing to cysteine homeostasis. Potential applications of our results should now be investigated in the context of renal failure and other disorders associated with cystinosis caused by CTNS dysfunction.     

Melanin content and MC1R function independently affect UVR‐induced DNA damage in cultured human melanocytes

Malignant transformation of melanocytes leads to melanoma, the most fatal form of skin cancer. Ultraviolet radiation (UVR)‐induced DNA photoproducts play an important role in melanomagenesis. Cutaneous melanin content represents a major photoprotective mechanism against UVR‐induced DNA damage, and generally correlates inversely with the risk of skin cancer, including melanoma. Melanoma risk is also determined by susceptibility genes, one of which is the melanocortin 1 receptor (MC1R) gene. Certain MC1R alleles are strongly associated with melanoma. We hereby present experimental evidence for the role of two melanoma risk factors, constitutive pigmentation, as assessed by total melanin, eumelanin and pheomelanin contents, and MC1R genotype and function, in determining the induction and repair of DNA photoproducts in cultured human melanocytes after irradiation with increasing doses of UVR. We found that total melanin and eumelanin contents (MC and EC) correlated inversely with the extent of UVR‐induced growth arrest, apoptosis and induction of cyclobutane pyrimidine dimers (CPD), but not with hydrogen peroxide release in melanocytes expressing functional MC1R. In comparison, melanocytes with loss‐of‐function MC1R, regardless of their MC or EC, sustained more UVR‐induced apoptosis and CPD, and exhibited reduced CPD repair. Therefore, MC, mainly EC, and MC1R function are independent determinants of UVR‐induced DNA damage in melanocytes.     

SLC45A2 protein stability and regulation of melanosome pH determine melanocyte pigmentation

SLC45A2 encodes a putative transporter expressed primarily in pigment cells. SLC45A2 mutations cause oculocutaneous albinism type 4 (OCA4) and polymorphisms are associated with pigmentation variation, but the localization, function, and regulation of SLC45A2 and its variants remain unknown. We show that SLC45A2 localizes to a cohort of mature melanosomes that only partially overlaps with the cohort expressing the chloride channel OCA2. SLC45A2 expressed ectopically in HeLa cells localizes to lysosomes and raises lysosomal pH, suggesting that in melanocytes SLC45A2 expression, like OCA2 expression, results in the deacidification of maturing melanosomes to support melanin synthesis. Interestingly, OCA2 overexpression compensates for loss of SLC45A2 expression in pigmentation. Analyses of SLC45A2- and OCA2-deficient mouse melanocytes show that SLC45A2 likely functions later during melanosome maturation than OCA2. Moreover, the light skin-associated SLC45A2 allelic F374 variant restores only moderate pigmentation to SLC45A2-deficient melanocytes due to rapid proteasome-dependent degradation resulting in lower protein expression levels in melanosomes than the dark skin-associated allelic L374 variant. Our data suggest that SLC45A2 maintains melanosome neutralization that is initially orchestrated by transient OCA2 activity to support melanization at late stages of melanosome maturation, and that a common allelic variant imparts reduced activity due to protein instability.     

UV and melanoma: the TP53 link

Ultraviolet radiation (UVR) is a major risk factor for melanoma development, but it has been unclear exactly how UVR leads to melanomagenesis. In a recent publication in Nature, Viros et al. identify TP53/Trp53 as a UVR-target gene in melanoma and show that UVR-induced TP53/Trp53 mutations accelerate BRAF(V600E)-driven melanomagenesis.Melanoma is the deadliest skin cancer, and its incidence has relentlessly increased over recent decades. According to the American Cancer Society''s estimates for melanoma in the United States for 2014, about 76 100 new melanomas will be diagnosed and about 9 710 people are expected to die from melanoma. It is well known that UVR is the major environmental factor contributing to melanomagenesis¹. This suggests that there is at least a component of melanoma risk which may be preventable through UVR protective strategies — an issue of immense public health importance due to the availability of sunblocks and sun-safe behaviors. Importantly, while many studies have been conducted to elucidate the link between UVR and melanoma, the precise molecular mechanism(s) by which UVR triggers melanoma formation have remained incompletely understood.Recently, a powerful UVR-induced skin inflammatory response has been shown to provoke metastasis of melanoma² and the presence of UV signature mutations has also been reported throughout the melanoma exome, including recurrent melanoma genes such as RAC1, PPP6C, and STK19^3,4. Previous mouse models for UVR-induced melanoma revealed that UVR-induced inflammation promoted melanomagenesis in neonatal mice^5,6,7. These studies underlined UVR''s significant contribution to melanoma formation. In a recent study published in Nature, Viros et al.⁸ address the role of UVR in previously established BRAF(V600E)-expressing melanocytes in vivo, and demonstrate that significantly accelerated melanoma formation often associated with mutations in TP53/Trp53. To mimic both somatic mutation acquisition and mild sunburn in humans, BRAF(V600E) was expressed at physiological levels in adult mice which were subsequently exposed to repeated low doses of UVR. In addition, certain mice were partially covered with UVR-proof cloth or topically treated with SunSense Milk Sunscreen SPF50 (2.2 mg/cm²) 30 min before UVR exposure, to assess the impact of these protective strategies.UVR was seen to significantly accelerate melanoma formation in mice whose melanocytes express BRAF(V600E), but not in BRAF wild-type mice (which unlike BRAF(V600E)-expressing mice do not develop long latency melanomas independently of UVR). Application of UVR-proof cloth or sunscreen delayed the onset of UVR-driven melanoma and partially prevented acceleration of BRAF(V600E)-driven melanomagenesis by UVR, and sunscreen-protected UVR-exposed BRAF(V600E) mice developed a reduced number of melanomas compared with unprotected UVR-exposed BRAF(V600E) mice (Figure 1). More somatic single nucleotide variants and a significantly higher proportion of C-to-T transitions at the 3′ end of pyrimidine dimers were observed in UVR-exposed melanomas, providing direct evidence of UVR-induced DNA damage. In addition, Trp53 mutations (H39Y, S124F, R245C, R270C, C272G) were detected in UVR-exposed BRAF(V600E) mouse melanomas, indicating a direct role of UVR in the induction of Trp53 mutations in melanoma. The mutated corresponding residues (S127F/S124F, R248C/R245C, R273C/R270C, C275G/C272G) were also identified in TP53 mutations in human melanoma, suggesting that TP53 mutations are linked to evidence of UVR-induced DNA damage in human melanoma. These results are consistent with previous reports that p53 deletion accelerates BRAF(V600E)-driven melanomagenesis both in mice⁹ and in zebrafish¹⁰, but demonstrate the ability of UVR to inflict UV signature mutations within the gene as has been widely observed in non-melanoma skin cancers and also in human melanomas.Open in a separate windowFigure 1A diagram depicting feasible routes of BRAF(V600E)-driven melanomagenesis.This elegant study by Viros et al. clearly helps to establish key roles of UVR in melanomagenesis, and further validates the functional importance of TP53 as a UVR-targeted tumor suppressor gene in a fraction of melanomas. The study also raises several intriguing questions worthy of follow-up analysis. For example, through which mechanism(s) did sunscreen or sunshielding delay but not prevent UVR-induced melanoma? Induction of cutaneous inflammatory changes that are less anatomically restricted to UV irradiated fields, would seem to be an attractive mechanism. This may help to explain the known risk of melanoma in both sun-exposed and less-exposed skin of lightly pigmented people. It is also valuable to better understand the role of UVB vs UVA wavelengths in melanomagenesis. Mechanistically, these distinct regions of the UV spectrum inflict largely distinctive chemical alterations on the genome. Efforts to block UVA as well as UVB in commercial sunscreen products are currently being promoted by the US Food and Drug Administration, a welcome improvement to sun protection strategies. Still, the precise role(s) of UVA in melanomagenesis remain incompletely understood and may involve both cell-autonomous and non-cell-autonomous targets. In addition to the acceleration of BRAF(V600E)-driven melanoma formation by UVR, red pigment (pheomelanin) has also been observed to accelerate BRAF(V600E)-driven melanomagenesis even in the absence of UVR¹¹. Pheomelanin has been identified as an intrinsic risk factor for melanoma with the red pigment itself producing reactive oxygen species that cause DNA damage in the skin, and consequently promote melanomagenesis independently of UVR. UVR likely exacerbates red pigment-induced BRAF(V600E)-driven melanoma, and still remains as a major contributor to melanomagenesis. Therefore, along with UV shielding by sunscreens, further preventative strategies should be investigated to diminish UVR-independent melanoma risk mechanisms.Viros et al. provide intriguing answers to several controversial questions regarding melanomagenesis: Does UVR really trigger melanoma? And can sunscreen actually prevent melanoma? The studies by Viros et al. provide experimental evidence for acceleration of BRAF(V600E)-driven melanoma by UVR-induced TP53/Trp53 mutation and demonstrate that sunscreen delayed but did not completely block UVR-driven melanoma. The current study clearly shows that UVR boosts melanoma and sunscreens may provide partial UVR protection against melanoma — evidence which matches human epidemiologic data. Nevertheless, to protect the public from melanoma, Viros et al. advise that sunscreen should be utilized in combination with additional sun avoidance strategies. In addition, measures that may prevent UV-independent melanoma formation will require additional research and may also be needed in order to optimally battle the incidence of this life-threatening malignancy.     

MiR-139-5p/SLC7A11 inhibits the proliferation,invasion and metastasis of pancreatic carcinoma via PI3K/Akt signaling pathway

ObjectivePancreatic carcinoma (PANC) is one of the important aggressive cancers, with deficiency in effective therapeutics. The study aimed to investigate the effects and molecular mechanism of miR-139-5p/SLC7A11 on the proliferation and metastasis of PANC.MethodsBioinformatics was used to analyze the differentially expressed genes in the TCGA database. PANC cell lines with overexpressed miR-139-5p and Solute Carrier Family 7, Member 11 (SLC7A11) was established, and have been used to detect cell proliferation, invasion and metastasis of PANC Subsequently, bioinformatic analysis and dual luciferase reporter assay were performed to confirm that SLC7A11 was a target gene of miR-139-5p. Xenograft mice model was used to explore the functions of miR-139-5p in PANC tumorigenicity.ResultsMiR-139-5p could regulate and affect the protein expression of P13K and Akt associated with phosphatidylinositol signaling pathway by inhibiting SLC7A11. MiR-139-5p was found to be lowly expressed in PANC tissues, while SLC7A11 was highly expressed. Low expression of miR-139-5p and high expression of SLC7A11 were positively associated with poor clinical outcomes. PANC cell proliferation, invasion and metastasis could be inhibited by miR-139-5p overexpression and be promoted by SLC7A11 overexpression. MiR-139-5p overexpression could suppress PANC tumor growth and the expressions of SLC7A11, p-PI3K, p-Akt in tumor tissues. Therefore, the inhibitory of miR-139-5p to PANC cell proliferation, invasion and metastasis was partly due to its inhibiting effect on SLC7A11 expression.ConclusionOur study proves that miR-139-5p/SLC7A11 has important functions on PANC, suggesting that miR-139-5p can be used as a biomarker for PANC patients.     

Production of brown/yellow patches in the SLC7A11 transgenic sheep via testicular injection of transgene

The gene,SLC7A11,which encodes the solute carrier family 7 member 11(anionic amino acid transporter light chain,xCT),has been reported to be implicated in multiple processes such as in pheomelanin production,cell proliferation and migration,Kaposi’s sarcoma herpesvirus(KSHV) entry into the host cells,learning and memory.Its involvement in cancer cell proliferation and metastasis has been widely studied.Its role in pheomelanogenesis is likely conserved in sheep.The full-length cDNA of sheep SLC7A11 was cloned from sheep skin fibroblasts for evaluating its role in regulating sheep coat color.The complete open reading frame of sheep xCT(sxCT) is 1512 bp in length,encoding a 503 amino acid polypeptide.We explored its function on pheomelanogenesis in vitro and in vivo.In the melan-a non-agouti mouse melanocytes that mainly produce eumelanin,overexpressed sxCT reduced the content of eumelanin.Using a testicular injection transgenic method,sxCT-transgenic sheep were generated and exhibited patches of brown/yellow coat,suggesting that sxCT can be selectively expressed to increase the pheomelanin production in wool.Our studies suggest that testicular injection of transgene can be used to genetically modify sheep coat color.     

SLC7 amino acid transporters of the yellow fever mosquito Aedes aegypti and their role in fat body TOR signaling and reproduction

BackgroundAn important function of the fat body in adult female mosquitoes is the conversion of blood meal derived amino acids (AA) into massive amounts of yolk protein precursors. A highly efficient transport mechanism for AAs across the plasma membrane of the fat body trophocytes is essential in order to deliver building blocks for the rapid synthesis of large amounts of these proteins. This mechanism consists in part of AA transporter proteins from the solute carrier family. These transporters have dual function; they function as transporters and participate in the nutrient signal transduction pathway that is activated in the fat body after a blood meal. In this study we focused on the solute carrier 7 family (SLC7), a family of AA transporters present in all metazoans that includes members with strong substrate specificity for cationic AAs.Methodology/principal findingsWe identified 11 putative SLC7 transporters in the genome sequence of Aedes aegypti. Phylogenetic analysis puts five of these in the cationic AA transporter subfamily (CAT) and six in the heterodimeric AA transporter (HAT) subfamily. All 11 A. aegypti SLC7 genes are expressed in adult females. Expression profiles are dynamic after a blood meal. We knocked down six fat body-expressed SLC7 transporters using RNAi and found that these ‘knockdowns’ reduced AA-induced TOR signaling. We also determined the effect these knockdowns had on the number of eggs deposited following a blood meal.Conclusions/significanceOur analysis stresses the importance of SLC7 transporters in TOR signaling pathway and mosquito reproduction.     

Melanin content and MC1R function independently affect UVR-induced DNA damage in cultured human melanocytes

Malignant transformation of melanocytes leads to melanoma, the most fatal form of skin cancer. Ultraviolet radiation (UVR)-induced DNA photoproducts play an important role in melanomagenesis. Cutaneous melanin content represents a major photoprotective mechanism against UVR-induced DNA damage, and generally correlates inversely with the risk of skin cancer, including melanoma. Melanoma risk is also determined by susceptibility genes, one of which is the melanocortin 1 receptor (MC1R) gene. Certain MC1R alleles are strongly associated with melanoma. We hereby present experimental evidence for the role of two melanoma risk factors, constitutive pigmentation, as assessed by total melanin, eumelanin and pheomelanin contents, and MC1R genotype and function, in determining the induction and repair of DNA photoproducts in cultured human melanocytes after irradiation with increasing doses of UVR. We found that total melanin and eumelanin contents (MC and EC) correlated inversely with the extent of UVR-induced growth arrest, apoptosis and induction of cyclobutane pyrimidine dimers (CPD), but not with hydrogen peroxide release in melanocytes expressing functional MC1R. In comparison, melanocytes with loss-of-function MC1R, regardless of their MC or EC, sustained more UVR-induced apoptosis and CPD, and exhibited reduced CPD repair. Therefore, MC, mainly EC, and MC1R function are independent determinants of UVR-induced DNA damage in melanocytes.     

Low-quality birds do not display high-quality signals: The cysteine-pheomelanin mechanism of honesty

The mechanisms that make that the costs of producing high-quality signals are unaffordable to low-quality signalers are a current issue in animal communication. The size of the melanin-based bib of male house sparrows Passer domesticus honestly signals quality. We induced the development of new bibs while treating males with buthionine-sulfoximine (BSO), a substance that depletes the levels of the antioxidant glutathione (GSH) and the amino acid cysteine, two elements that switch melanogenesis from eumelanin to pheomelanin. Final bib size is negatively related to pheomelanin levels in the bib feathers. BSO reduced cysteine and GSH levels in all birds, but improved phenotypes (bibs larger than controls) were only expressed by high-quality birds (BSO birds with largest bibs initially). Negative associations between final bib size and cysteine levels in erythrocytes, and between pheomelanin and cysteine levels, were observed in high-quality birds only. These findings suggest that a mechanism uncoupling pheomelanin and cysteine levels may have evolved in low-quality birds to avoid producing bibs of size not corresponding to their quality and greater relative costs. Indeed, greater oxidative stress in cells was not observed in low-quality birds. This may represent the first mechanism maintaining signal honesty without producing greater relative costs on low-quality signalers.     

The Mutant p53-Targeting Compound APR-246 Induces ROS-Modulating Genes in Breast Cancer Cells

TP53 is the most frequently mutated gene in human cancer and thus an attractive target for novel cancer therapy. Several compounds that can reactive mutant p53 protein have been identified. APR-246 is currently being tested in a phase II clinical trial in high-grade serous ovarian cancer. We have used RNA-seq analysis to study the effects of APR-246 on gene expression in human breast cancer cell lines. Although the effect of APR-246 on gene expression was largely cell line dependent, six genes were upregulated across all three cell lines studied, i.e., TRIM16, SLC7A11, TXNRD1, SRXN1, LOC344887, and SLC7A11-AS1. We did not detect upregulation of canonical p53 target genes such as CDKN1A (p21), 14-3-3σ, BBC3 (PUMA), and PMAIP1 (NOXA) by RNA-seq, but these genes were induced according to analysis by qPCR. Gene ontology analysis showed that APR-246 induced changes in pathways such as response to oxidative stress, gene expression, cell proliferation, response to nitrosative stress, and the glutathione biosynthesis process. Our results are consistent with the dual action of APR-246, i.e., reactivation of mutant p53 and modulation of redox activity. SLC7A11, TRIM16, TXNRD1, and SRXN1 are potential new pharmacodynamic biomarkers for assessing the response to APR-246 in both preclinical and clinical studies.     

Aberrant CpG methylation of the TFAP2A gene constitutes a mechanism for loss of TFAP2A expression in human metastatic melanoma

Metastatic melanoma is a deadly treatment-resistant form of skin cancer whose global incidence is on the rise. During melanocyte transformation and melanoma progression the expression profile of many genes changes. Among these, a gene implicated in several steps of melanocyte development, TFAP2A, is frequently silenced; however, the molecular mechanism of TFAP2A silencing in human melanoma remains unknown. In this study, we measured TFAP2A mRNA expression in primary human melanocytes compared to 11 human melanoma samples by quantitative real-time RT-PCR. In addition, we assessed CpG DNA methylation of the TFAP2A promoter in these samples using bisulfite sequencing. Compared to primary melanocytes, which showed high TFAP2A mRNA expression and no promoter methylation, human melanoma samples showed decreased TFAP2A mRNA expression and increased promoter methylation. We further show that increased CpG methylation correlates with decreased TFAP2A mRNA expression. Using The Cancer Genome Atlas, we further identified TFAP2A as a gene displaying among the most decreased expression in stage 4 melanomas vs. non-stage 4 melanomas, and whose CpG methylation was frequently associated with lack of mRNA expression. Based on our data, we conclude that TFAP2A expression in human melanomas can be silenced by aberrant CpG methylation of the TFAP2A promoter. We have identified aberrant CpG DNA methylation as an epigenetic mark associated with TFAP2A silencing in human melanoma that could have significant implications for the therapy of human melanoma using epigenetic modifying drugs.     

Upregulation of the solute carrier family 7 genes is indicative of poor prognosis in papillary thyroid carcinoma

Background

The solute carrier (SLC) 7 family genes comprise 14 members and function as cationic amino acid/glycoprotein transporters in many cells, they are essential for the maintenance of amino acid nutrition and survival of tumor cells. This study was conducted to analyze the associations of SLC7 family gene expression with mortality in papillary thyroid carcinoma (PTC).

Methods

Clinical features, somatic mutations, and SLC7 family gene expression data were downloaded from The Cancer Genome Atlas database. Linear regression model analysis was performed to analyze the correlations between SLC7 family gene expression and clinicopathologic features. Kaplan-Meier survival and logistic regression analyses were performed to characterize the associations between gene expression and patients’ overall survival.

Results

Patient mortality was negatively associated with age and tumor size but positively increased cancer stage and absence of thyroiditis in PTC patients. Kaplan-Meier survival analysis indicated that patients with high SLC7A3, SLC7A5, and SLC7A11 expression levels exhibited poorer survival than those with low SLC7A3, SLC7A5, and SLC7A11 expression levels (P?<?0.05 for all cases). Logistic regression analysis showed that SLC7A3, SLC7A5, and SLC7A11 were associated with increased mortality (odds ratio [OR] 8.61, 95% confidence interval [CI] 2.3–55.91; OR 3.87, 95% CI 1.18–17.31; and OR 3.87, 95% CI 1.18–17.31, respectively.

Conclusion

Upregulation of SLC7A3, SLC7A5, and SLC7A11 expression was associated with poor prognosis in PTC patients, and SLC7 gene expression levels are potentially useful prognostic biomarkers.