Functional RET G691S polymorphism in cutaneous malignant melanoma

Genomic and transcriptomic analyses unveil the genetic basis of green shank trait in small white-feather chickens

Small white-feather chickens (SWFC) have become popular as a hybrid strain recently. Shank color is a notable economic trait in this strain. Despite numerous studies on the green shank trait from both physiological and genetic perspectives, research focusing specifically on the green shank trait in hybrid chickens (HC) remains limited. In this study, to investigate the genetic mechanisms and molecular basis of the green shank trait in HC, we created a population by intercrossing white-feathered and yellow-feathered broilers, both with yellow shanks. Physiological analysis confirmed that melanin deposition in the shank dermis is the primary cause of the green shank trait in HC. By combining genome-wide association studies (GWAS) and population genomics analysis, the 83.20-85.68 Mb region on the Z chromosome was identified as a candidate region for the green shank trait in HC. Transcriptome sequencing revealed differentially expressed genes (DEGs) between green shank and yellow shank individuals, with MTAP and CDKN1A identified as candidate genes in the genomic region associated with the green shank trait. Notably, the green shank trait includes a light green phenotype. Our study is the first to identify genes associated with different color depths of the green shank. The candidate genes influence both the biosynthesis and deposition of pigments.

Top 10 Differential Diagnoses for Desmoplastic Melanoma

BACKGROUND

Desmoplastic melanoma is a rare subtype of melanoma mainly appearing on sun-exposed skin. Clinically, it is many times non-pigmented and therefore the diagnosis is often not suspected.

METHODS

Review article.

RESULTS

In this paper we review the main histopathological, immunohistochemical, and molecular features of desmoplastic melanoma, as well as the top 10 morphologic differential diagnoses which should be considered in most cases. The histopathological pattern can be many times deceptive, mimicking a scar, a fibrous reaction, a fibrohistiocytic tumor such as a dermatofibroma, a vascular tumor such as angiosarcoma, a smooth muscle tumor such as leiomyosarcoma, or a neural tumor. Although an overlying atypical junctional melanocytic proliferation may be seen in most cases, it is absent in a significant percentage (up to 30%) of cases, making the diagnosis even more difficult in those instances. The range of diagnostic pitfalls is wide, which may present disastrous prognostic consequences.

CONCLUSION

Desmoplastic melanoma is often a difficult diagnosis to make, as it frequently shows nonspecific clinical findings and overlapping histologic features with many other tumors. However, the potential clinical and prognostic consequences of misdiagnosis as another entity are great. Therefore, this diagnosis must always be kept in mind when encountering spindle cell tumors affecting the head and neck area.

Genomic Profiling of Metastatic Basal cell Carcinoma Reveals Candidate Drivers of Disease and Therapeutic Targets

Basal cell carcinomas (BCCs) are human beings' most common malignant tumors. Most are easily managed by surgery or topical therapies, and metastasis is rare. Although BCCs can become locally advanced, metastatic BCCs are very uncommon and may be biologically distinct. We assessed the clinicopathologic characteristics of 17 patients with metastatic BCC and pursued whole-exome sequencing of tumor and germline DNA from 8 patients. Genomic profiling revealed aberrant activation of Hedgehog signaling and alterations in GLI transcriptional regulators and Notch and Hippo signaling. Matched local recurrences of primary BCCs and metastases from 3 patients provided evidence of a clonal origin in all cases. Mutations associated with YAP inhibition were found exclusively in 2 hematogenously-spread lung metastases, and metastatic BCCs were enriched for mutations in the YAP/TAZ-binding domain of TEAD genes. Accordingly, YAP/TAZ nuclear localization was associated with metastatic types and Hippo mutations, suggesting an enhanced oncogenic role in hematogenously-spread metastases. Mutations in RET, HGF, and phosphatidylinositol 3‑kinase (PI3K)/protein kinase B (AKT) signaling were enriched compared with a cohort of low clinical-risk BCCs. Our results implicate Hippo and PI3K/AKT dysregulation in metastatic progression of BCCs, making these potential therapeutic targets in metastatic disease. The common clonal origin of matched recurrent and metastatic BCCs suggests that molecular profiling can assist in determining the nature/origin of poorly differentiated metastatic tumors of uncertain type. Genes and pathways enriched for mutations in this cohort are candidate drivers of metastasis and can be used to identify patients at high risk of metastasis who may benefit from aggressive local treatment and careful clinical follow-up.

Targeting Rearranged during Transfection in Cancer: A Perspective on Small-Molecule Inhibitors and Their Clinical Development

Rearranged during transfection (RET) is a receptor tyrosine kinase essential for the normal development and maturation of a diverse range of tissues. Aberrant RET signaling in cancers, due to RET mutations, gene fusions, and overexpression, results in the activation of downstream pathways promoting survival, growth, and metastasis. Pharmacological manipulation of RET is effective in treating RET-driven cancers, and efforts toward developing RET-specific therapies have increased over the last 5 years. In 2020, RET-selective inhibitors pralsetinib and selpercatinib achieved clinical approval, which marked the first approvals for kinase inhibitors specifically developed to target the RET oncoprotein. This Perspective discusses current development and clinical applications for RET precision medicine by providing an overview of the incremental improvement of kinase inhibitors for use in RET-driven malignancies.

LncRNA-HNF1A-AS1 functions as a competing endogenous RNA to activate PI3K/AKT signalling pathway by sponging miR-30b-3p in gastric cancer

BACKGROUND

Accumulating evidence demonstrated that long noncoding RNAs (lncRNAs) played important regulatory roles in many cancer types. However, the role of lncRNAs in gastric cancer (GC) progression remains unclear.

METHODS

RT-qPCR assay was performed to detect the expression of HNF1A-AS1 in gastric cancer tissues and the non-tumourous gastric mucosa. Overexpression and RNA interference approaches were used to investigate the effects of HNF1A-AS1 on GC cells. Insight into competitive endogenous RNA (ceRNA) mechanisms was gained via bioinformatics analysis, luciferase assays and an RNA-binding protein immunoprecipitation (RIP) assay, RNA-FISH co-localisation analysis combined with microRNA (miRNA)-pulldown assay.

RESULTS

This study displayed that revealed expression of HNF1A-AS1 was associated with positive lymph node metastasis in GC. Moreover, HNF1A-AS1 significantly promoted gastric cancer invasion, metastasis, angiogenesis and lymphangiogenesis in vitro and in vivo. In addition, HNF1A-AS1 was demonstrated to function as a ceRNA for miR-30b-3p. HNF1A-AS1 abolished the function of the miRNA-30b-3p and resulted in the derepression of its target, PIK3CD, which is a core oncogene involved in the progression of GC.

CONCLUSION

This study demonstrated that HNF1A-AS1 worked as a ceRNA and promoted PI3K/AKT signalling pathway-mediated GC metastasis by sponging miR-30b-3p, offering novel insights of the metastasis mechanism in GC.

Oncogenic and drug-sensitive RET mutations in human epithelial ovarian cancer

Background

Epithelial ovarian cancer (EOC) is a highly lethal malignancy. Improvement in genetic characterization of EOC patients is required to propose new potential targets, since surgical resection coupled to chemotherapy, presents several limits such as cancer recurrence and drug resistance. Targeted therapies have more efficacy and less toxicity than standard treatments. One of the most relevant cancer-specific actionable targets are protein tyrosine kinases (PTKs) whose role in EOC need to be better investigated.

Methods

EOC genomic datasets are retrieved and analyzed. The biological and clinical significance of RET genomic aberrations in ovarian cancer context are investigated by a series of in vitro and in vivo experiments.

Results

Epithelial ovarian cancer sequencing projects identify recurrent genomic RET missense mutations in 1.98% of patients, ranking as the top-five hit among the 100 receptor tyrosine kinases-encoding genes. RET mutants R693H and A750T show oncogenic transformation properties in NIH3T3 cells. Introduction of the RET mutants into human EOC cells increases RET signaling, cell viability, anchorage-independent cell growth and tumor xenograft growth in nude mice, demonstrating that they are activating mutations. RET mutants significantly enhance the activation of RET and its downstream MAPK and AKT signaling pathway in ovarian cancer cells. Vandetanib, a clinical approved RET inhibitor, inhibits the cell viability and decreases the activation of RET-MAPK signaling pathways in EOC cells expressing oncogenic RET mutants.

Conclusions

The discovery of RET pathogenic variants in the EOC patients, suggests a previously underestimated role for RET in EOC tumorigenesis. The identification of the gain-of-function RET mutations in EOC highlights the potential use of RET in targeted therapy to treat ovarian cancer patients.

Differing biologic behaviors of desmoplastic melanoma subtypes: Insights based on histopathologic, immunohistochemical, and genetic analyses

Desmoplastic melanoma (DM) is an uncommon variant of melanoma that can be challenging to diagnose. Phenotypic variations in terms of the proportion of spindled cells and fibromucinous stroma have led to the subclassification of pure (>90% spindled cells) and mixed (<90% spindled cells admixed with epithelioid cells) histopathologic DM subtypes. This subclassification is not just semantic; several studies have underscored differences in clinical and prognostic behaviors of the subtypes. In this review, we parse the literature on DM subtypes with an emphasis on histopathologic, immunohistochemical, and genetic data to ascertain whether these factors influence and/or affect their differing biological behaviors. Demographics regarding age, location, and clinical behavior of the subtypes are detailed, as is the impact of dermoscopy as a diagnostic adjunct. Despite the plethora of markers used, our findings suggest that few differentiate between the DM subtypes. Differential expression of PD-L1 suggests that patients with the mixed subtype are likely better candidates for anti-PD/PD-L1 therapy. Significant differences between the subtypes in terms of neurofibromin expression and the frequency of TERT promoter mutations suggest that the subtypes have distinct genetic drivers. Thus, immunohistochemical and genetic analyses imply that these likely affect the biological behaviors of the DM subtypes.

RET fusions in solid tumors

The RET proto-oncogene has been well-studied. RET is involved in many different physiological and developmental functions. When altered, RET mutations influence disease in a variety of organ systems from Hirschsprung's disease and multiple endocrine neoplasia 2 (MEN2) to papillary thyroid carcinoma (PTC) and non-small cell lung cancer (NSCLC). Changes in RET expression have been discovered in 30-70% of invasive breast cancers and 50-60% of pancreatic ductal adenocarcinomas in addition to colorectal adenocarcinoma, melanoma, small cell lung cancer, neuroblastoma, and small intestine neuroendocrine tumors. RET mutations have been associated with tumor proliferation, invasion, and migration. RET fusions or rearrangements are somatic juxtapositions of 5' sequences from other genes with 3' RET sequences encoding tyrosine kinase. RET rearrangements occur in approximately 2.5-73% of sporadic PTC and 1-3% of NSCLC patients. The most common RET fusions are CDCC6-RET and NCOA4-RET in PTC and KIF5B-RET in NSCLC. Tyrosine kinase inhibitors are drugs that target kinases such as RET in RET-driven (RET-mutation or RET-fusion-positive) disease. Multikinase inhibitors (MKI) target various kinases and other receptors. Several MKIs are FDA-approved for cancer therapy (sunitinib, sorafenib, vandetanib, cabozantinib, regorafenib, ponatinib, lenvatinib, alectinib) and non-oncologic disease (nintedanib). Selective RET inhibitor drugs LOXO-292 (selpercatinib) and BLU-667 (pralsetinib) are also undergoing phase I/II and I clinical trials, respectively, with preliminary results demonstrating partial response and low incidence of serious adverse events. RET fusions provide a viable therapeutic target for oncologic treatment, and further study is warranted into the prevalence and pathogenesis of RET fusions as well as development of current and new tyrosine kinase inhibitors.

Expression of RET is associated with Oestrogen receptor expression but lacks prognostic significance in breast cancer

BACKGROUND

The Rearranged during Transfection (RET) protein is overexpressed in a subset of Estrogen Receptor (ER) positive breast cancer, with both signalling pathways functionally interacting. This cross-talk plays a pivotal role in the resistance of breast cancer cells to anti-endocrine therapies, and RET expression is assumed to correlate with poor prognosis based on findings in small patient cohorts. The aim of our study was to investigate the impact of RET expression on patient outcome in human breast cancer.

METHODS

We performed an immunohistochemical analysis of RET protein expression on a tissue microarray encompassing 990 breast cancer patients and correlated its expression with clinicopathological parameters and survival data.

RESULTS

Expression of RET was detected in 409 out of 990 cases (41.3%). RET and ER expression significantly correlated (p < 0.0001). The Luminal B HER2-positive subtype showed the highest expression rate (48.9%). In univariate and multivariate survival analyses, RET expression had no impact on overall survival.

CONCLUSION

We confirmed the co-expression of RET and ER, but we did not find RET expression to be an independent prognostic factor in human breast cancer. Clinical trials with newly developed RET inhibitors are needed to evaluate if RET inhibition has a beneficial impact on patient survival in ER positive breast cancer.

GDNF and the RET Receptor in Cancer: New Insights and Therapeutic Potential

The Glial cell line-derived neurotrophic Family Ligands (GFL) are soluble neurotrophic factors that are required for development of multiple human tissues, but which are also important contributors to human cancers. GFL signaling occurs through the transmembrane RET receptor tyrosine kinase, a well-characterized oncogene. GFL-independent RET activation, through rearrangement or point mutations occurs in thyroid and lung cancers. However, GFL-mediated activation of wildtype RET is an increasingly recognized mechanism promoting tumor growth and dissemination of a much broader group of cancers. RET and GFL expression have been implicated in metastasis or invasion in diverse human cancers including breast, pancreatic, and prostate tumors, where they are linked to poorer patient prognosis. In addition to directly inducing tumor growth in these diseases, GFL-RET signaling promotes changes in the tumor microenvironment that alter the surrounding stroma and cellular composition to enhance tumor invasion and metastasis. As such, GFL RET signaling is an important target for novel therapeutic approaches to limit tumor growth and spread and improve disease outcomes.

65 YEARS OF THE DOUBLE HELIX: Exploiting insights on the RET receptor for personalized cancer medicine

The focus of precision cancer medicine is the use of patient genetic signatures to predict disease occurrence and course and tailor approaches to individualized treatment to improve patient outcomes. The rearranged during transfection (RET) receptor tyrosine kinase represents a paradigm for the power of personalized cancer management to change cancer impact and improve quality of life. Oncogenic activation of RET occurs through several mechanisms including activating mutations and increased or aberrant expression. Activating RET mutations found in the inherited cancer syndrome multiple endocrine neoplasia 2 permit early diagnosis, predict disease course and guide disease management to optimize patient survival. Rearrangements of RET found in thyroid and lung tumors provide insights on potential disease aggressiveness and offer opportunities for RET-targeted therapy. Aberrant RET expression in a subset of cases is associated with tumor dissemination, resistance to therapies and/or poorer prognosis in multiple cancers. The potential of RET targeting through repurposing of small-molecule multikinase inhibitors, selective RET inhibitors or other novel approaches provides exciting opportunities to individualize therapies across multiple pathologies where RET oncogenicity contributes to cancer outcomes.

Association of medullary sponge kidney and hyperparathyroidism with RET G691S/S904S polymorphism: a case report

Background

Medullary sponge kidney is a rare renal malformation, which usually manifests as nephrocalcinosis, renal tubular acidosis, and recurrent urinary tract infections. Medullary sponge kidney is often associated with renal developmental anomalies and tumors, and its exact pathogenesis is not yet clearly explained. Given the key role of the interaction of glial cell line-derived neurotrophic factor gene, GDNF, and the “rearranged during transfection” proto-oncogene, RET, in kidney and urinary tract development, variations in these genes are proposed to be candidates for medullary sponge kidney. Hyperparathyroidism is observed in a few patients with medullary sponge kidney, but the exact pathogenesis of this association is unknown. This case report highlights the coexistence of these two conditions associated with RET polymorphism, which contributes toward the understanding of the pathogenesis of medullary sponge kidney.

Case presentation

A 52-year-old Chinese woman with recurrent renal stones presented to our hospital. Subsequently she was diagnosed as having medullary sponge kidney and tertiary hyperparathyroidism and underwent parathyroidectomy. Genomic DNA was isolated from lymphocytes and the GDNF and RET genes were determined by Sanger sequencing. Two RET polymorphisms were found in our patient, one was nonsynonymous c.2071G>A (G691S; rs1799939) located in exon 11, the other was synonymous c.2712C>G. (p.S904S; rs1800863) located in exon 15.

Conclusions

We demonstrated a case of medullary sponge kidney combined with tertiary hyperparathyroidism, which contributes to further understanding of the pathogenesis of this disease. Besides, we also found RET G691S/S904S polymorphism in this patient, but additional studies are required to explore the role of the RET gene in medullary sponge kidney with hyperparathyroidism.

The GDNF Family: A Role in Cancer?

The glial cell line-derived neurotrophic factor (GDNF) family of ligands (GFLs) comprising of GDNF, neurturin, artemin, and persephin plays an important role in the development and maintenance of the central and peripheral nervous system, renal morphogenesis, and spermatogenesis. Here we review our current understanding of GFL biology, and supported by recent progress in the area, we examine their emerging role in endocrine-related and other non-hormone-dependent solid neoplasms. The ability of GFLs to elicit actions that resemble those perturbed in an oncogenic phenotype, alongside mounting evidence of GFL involvement in tumor progression, presents novel opportunities for therapeutic intervention.

Kinase gene fusions in defined subsets of melanoma

Genomic rearrangements resulting in activating kinase fusions have been increasingly described in a number of cancers including malignant melanoma, but their frequency in specific melanoma subtypes has not been reported. We used break-apart fluorescence in situ hybridization (FISH) to identify genomic rearrangements in tissues from 59 patients with various types of malignant melanoma including acral lentiginous, mucosal, superficial spreading, and nodular. We identified four genomic rearrangements involving the genes BRAF, RET, and ROS1. Of these, three were confirmed by Immunohistochemistry (IHC) or sequencing and one was found to be an ARMC10-BRAF fusion that has not been previously reported in melanoma. These fusions occurred in different subtypes of melanoma but all in tumors lacking known driver mutations. Our data suggest gene fusions are more common than previously thought and should be further explored particularly in melanomas lacking known driver mutations.

A Multikinase and DNA-PK Inhibitor Combination Immunomodulates Melanomas, Suppresses Tumor Progression, and Enhances Immunotherapies

Combination therapies have the potential to improve outcomes in melanoma patients but have not yet been clinically efficacious. Here, we used high-throughput flow cytometry-based screening to identify and characterize candidate therapies that might synergize with and augment T-cell immunotherapy efficacy. Two lead therapies, regorafenib (Reg) and NU7441, were selected based on their ability to alter a variety of immunomodulatory proteins, including CD55, CD73, CD155, programmed death-ligand 1 (PD-L1), nerve growth factor receptor (NGFR), and HLA class I in a heterogeneous panel of melanomas. The therapies also upregulated several melanoma antigens, inhibited proliferation, and perturbed activation of oncogenic signaling pathways in melanomas. T cells treated with the therapies proliferated normally and exhibited a favorably altered phenotype, including increased CD25, CD28, inducible T-cell costimulator (ICOS), and reduced expression of coinhibitory receptors. Cytokine production was also increased in treated T cells. When administered in mice, REg suppressed melanoma progression in a CD8⁺ T cell-dependent manner when used alone and with various immunotherapies. Additionally, Reg altered the number, phenotype, and function of various T-cell subsets in the tumor microenvironment. These studies reveal that Reg and NU7441 influence the immunobiology of both tumor cells and T cells and enhance the efficacy of various immunotherapies. Cancer Immunol Res; 5(9); 790-803. ©2017 AACR.

Epigenetic Regulation of KPC1 Ubiquitin Ligase Affects the NF-κB Pathway in Melanoma

Purpose: Abnormal activation of the NF-κB pathway induces a more aggressive phenotype of cutaneous melanoma. Understanding the mechanisms involved in melanoma NF-κB activation may identify novel targets for this pathway. KPC1, an E3 ubiquitin ligase, is a regulator of the NF-κB pathway. The objective of this study was to investigate the mechanisms regulating KPC1 expression and its clinical impact in melanoma.Experimental Design: The clinical impact of KPC1 expression and its epigenetic regulation were assessed in large cohorts of clinically well-annotated melanoma tissues (tissue microarrays; n = 137, JWCI cohort; n = 40) and The Cancer Genome Atlas database (TCGA cohort, n = 370). Using melanoma cell lines, we investigated the functional interactions between KPC1 and NF-κB, and the epigenetic regulations of KPC1, including DNA methylation and miRNA expression.Results: We verified that KPC1 suppresses melanoma proliferation by processing NF-κB1 p105 into p50, thereby modulating NF-κB target gene expression. Concordantly, KPC1 expression was downregulated in American Joint Committee on Cancer stage IV melanoma compared with early stages (stage I/II P = 0.013, stage III P = 0.004), and low KPC1 expression was significantly associated with poor overall survival in stage IV melanoma (n = 137; HR 1.810; P = 0.006). Furthermore, our data showed that high miR-155-5p expression, which is controlled by DNA methylation at its promoter region (TCGA; Pearson's r -0.455; P < 0.001), is significantly associated with KPC1 downregulation (JWCI; P = 0.028, TCGA; P = 0.003).Conclusions: This study revealed novel epigenetic regulation of KPC1 associated with NF-κB pathway activation, promoting metastatic melanoma progression. These findings suggest the potential utility of KPC1 and its epigenetic regulation as theranostic targets. Clin Cancer Res; 23(16); 4831-42. ©2017 AACR.

Copy number variation in archival melanoma biopsies versus benign melanocytic lesions

BACKGROUND

Skin melanocytes can give rise to benign and malignant neoplasms. Discrimination of an early melanoma from an unusual/atypical benign nevus can represent a significant challenge. However, previous studies have shown that in contrast to benign nevi, melanoma demonstrates pervasive chromosomal aberrations.

OBJECTIVE

This substantial difference between melanoma and benign nevi can be exploited to discriminate between melanoma and benign nevi.

METHODS

Array-comparative genomic hybridization (aCGH) is an approach that can be used on DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues to assess the entire genome for the presence of changes in DNA copy number. In this study, high resolution, genome-wide single-nucleotide polymorphism (SNP) arrays were utilized to perform comprehensive and detailed analyses of recurrent copy number aberrations in 41 melanoma samples in comparison with 21 benign nevi.

RESULTS

We found statistically significant copy number gains and losses within melanoma samples. Some of the identified aberrations are previously implicated in melanoma. Moreover, novel regions of copy number alterations were identified, revealing new candidate genes potentially involved in melanoma pathogenesis.

CONCLUSIONS

Taken together, these findings can help improve melanoma diagnosis and introduce novel melanoma therapeutic targets.

Genomic profiling of invasive melanoma cell lines by array comparative genomic hybridization

Malignant melanoma is one of the most aggressive human cancers. Invasion of cells is the first step in metastasis, resulting in cell migration through tissue compartments. We aimed to evaluate genomic alterations specifically associated with the invasive characteristics of melanoma cells. Matrigel invasion assays were used to determine the invasive properties of cell lines that originated from primary melanomas. Array comparative genomic hybridization analyses were carried out to define the chromosome copy number alterations (CNAs). Several recurrent CNAs were identified by array comparative genomic hybridization that affected melanoma-related genes. Invasive primary cell lines showed high frequencies of CNAs, including the loss of 7q and gain of 12q chromosomal regions targeting PTPN12, ADAM22, FZD1, TFPI2, GNG11, COL1A2, SMURF1, VGF, RELN and GLIPR1 genes. Gain of the GDNF (5p13.1), GPAA1, PLEC and SHARPIN (8q24.3) genes was significantly more frequent in invasive cell lines compared with the noninvasive ones. Importantly, copy number gains of these genes were also found in cell lines that originated from metastases, suggesting their role in melanoma metastasis formation. The present study describes genomic differences between invasive and noninvasive melanoma cell lines that may contribute toward the aggressive phenotype of human melanoma cells.

NF1 and Neurofibromin: Emerging Players in the Genetic Landscape of Desmoplastic Melanoma

Neurofibromatosis type I (NF1), a monogenic disorder with an autosomal dominant mode of inheritance, is caused by alterations in the NF1 gene which codes for the protein neurofibromin. Functionally, NF1 is a tumor suppressor as it is GTPase-activating protein that negatively regulates the MAPK pathway. More recently, much attention has focused on the role of NF1 and neurofibromin in melanoma as mutations in NF1 have been found to constitute 1 of the 4 distinct genomic categories of melanoma, with the other 3 comprising BRAF, NRAS, and "triple-wild-type" subtypes. In this review, we parse the literature on NF1 and neurofibromin with a view to clarifying and gaining a better understanding of their precise role/s in melanomagenesis. We begin with a historic overview, followed by details regarding structure and function and characterization of neural crest development as a model for genetic reversion in neoplasia. Melanogenesis in NF1 sets the stage for the discussion on the roles of NF1 and neurofibromin in neural crest-derived neoplasms including melanoma with particular emphasis on NF1 and neurofibromin as markers of melanocyte dedifferentiation in desmoplastic melanoma.

Neurotrophin Receptors and Perineural Invasion: Analyses in Select Lineage-Unrelated Cutaneous Malignancies With a Propensity for Perineural Invasion

In this chapter, we parse the literature on neurotrophins that have been implicated in the pathogenesis of perineural invasion (PNI) in select lineage-unrelated malignancies. We also detail evidence linking neurotrophins and their receptors (TrkA, RET, p75NGFR, and NCAM) to the pathogenesis of PNI in desmoplastic melanoma and cutaneous squamous cell carcinoma-both malignancies with an established propensity for PNI. Lastly, the clinical potential of neurotrophins as receptors for targeted therapies is explored.

Ki-67, p53, and p16 expression, and G691S RET polymorphism in desmoplastic melanoma (DM): A clinicopathologic analysis of predictors of outcome

BACKGROUND

The prognostic role Ki-67, p53, and p16 immunostains and RET (rearranged during transfection) polymorphism in desmoplastic melanoma has not been evaluated.

OBJECTIVE

We sought to identify potential prognostic markers.

METHODS

We performed Ki-67, p53, and p16 immunostains on 66 desmoplastic melanomas, and sequenced RET G691 polymorphism and recurrent mutations of 17 cancer genes in 55 and 20 cases, respectively.

RESULTS

Recurrence and metastasis were documented in 11 of 66 (17%) and 26 of 66 (39%) patients, respectively. Death was noted in 25 of 55 (45%) patients. Ki-67 expression (≥10%, 43%) correlated with male gender (P = .009), ulceration (P = .002), and Breslow depth (P = .009). p53 Expression (≥50%, 28%) correlated with male gender (P = .002) and head and neck location (P = .0228). Using Kaplan-Meier plots, Ki-67 expression (P = .0425) and mitosis (P = .00295) correlated with overall survival, whereas vascular invasion (P = .0292) correlated with disease progression. There was a significant correlation between Ki-67 and p53 expression (P = .003). RET polymorphism was present in 10 of 46 (22%) cases and inversely correlated with Breslow depth (P = .024).

LIMITATION

Our study is small and lacks power to perform a multivariate analysis.

CONCLUSION

Although Ki-67 expression correlated with overall survival, additional studies are needed to determine whether Ki-67 would be an independent prognostic marker in addition to the current routine histopathologic assessment.

RASSF8 regulates progression of cutaneous melanoma through nuclear factor-κb

Our group previously demonstrated that the RASSF1 gene has a significant tumor suppressor role in cutaneous melanoma. The RASSF8 gene is a member of the N-terminal RASSF gene family. Previously, we identified RASSF8 (HOJ1, NCBI Gene ID:11228) expression in cutaneous melanoma; however the functional role of RASSF8 in melanoma is not known. RASSF8 expression was assessed in melanoma cell lines and tumors of different AJCC stages. Results indicated that RASSF8 expression was low in metastatic melanoma lines and decreased with melanoma progression. We then explored the mechanism of RASSF8 downregulation in melanoma by assessing methylation of RASSF8 and demonstrated that methylation of RASSF8 gene promoter was higher in advanced than in early stages melanomas. Functional activity of RASSF8 in melanoma lines by knockdown and overexpression of RASSF8 demonstrated that RASSF8 expression significantly inhibited cell growth, cell migration and invasion, whereas knockdown of RASSF8 expression significantly increased cell growth, cell migration and invasion of melanoma cells by increasing expression of P65 and its downstream target IL-6. Moreover RASSF8 was found to induce apoptosis in melanoma cells by activating the P53-P21 pathway, and also in vivo studies demonstrated that inhibiting RASSF8 increases the tumorigenic properties of human melanoma xenografts. These results suggest that RASSF8 plays a significant role in suppressing the progression of cutaneous melanoma.

Therapy for BRAFi-Resistant Melanomas: Is WNT5A the Answer?

In recent years, scientists have advocated the use of targeted therapies in the form of drugs that modulate genes and proteins that are directly associated with cancer progression and metastasis. Malignant melanoma is a dreadful cancer type that has been associated with the rapid dissemination of primary tumors to multiple sites, including bone, brain, liver and lungs. The discovery that approximately 40%–50% of malignant melanomas contain a mutation in BRAF at codon 600 gave scientists a new approach to tackle this disease. However, clinical studies on patients have shown that although BRAFi (BRAF inhibitors) trigger early anti-tumor responses, the majority of patients later develop resistance to the therapy. Recent studies have shown that WNT5A plays a key role in enhancing the resistance of melanoma cells to BRAFi. The focus of the current review will be on melanoma development, signaling pathways important to acquired resistance to BRAFi, and why WNT5A inhibitors are attractive candidates to be included in combinatorial therapies for melanoma.

Suppression of Poly(rC)-Binding Protein 4 (PCBP4) reduced cisplatin resistance in human maxillary cancer cells

Cisplatin plays an important role in the therapy for human head and neck cancers. However, cancer cells develop cisplatin resistance, leading to difficulty in treatment and poor prognosis. To analyze cisplatin-resistant mechanisms, a cisplatin-resistant cell line, IMC-3CR, was established from the IMC-3 human maxillary cancer cell line. Flow cytometry revealed that, compared with IMC-3 cells, cisplatin more dominantly induced cell cycle G2/M arrest rather than apoptosis in IMC-3CR cells. That fact suggests that IMC-3CR cells avoid cisplatin-induced apoptosis through induction of G2/M arrest, which allows cancer cells to repair damaged DNA and survive. In the present study, we specifically examined Poly(rC)-Binding Protein 4 (PCBP4), which reportedly induces G2/M arrest. Results showed that suppression of PCBP4 by RNAi reduced cisplatin-induced G2/M arrest and enhanced apoptosis in IMC-3CR cells, resulting in the reduction of cisplatin resistance. In contrast, overexpression of PCBP4 in IMC-3 cells induced G2/M arrest after cisplatin treatment and enhanced cisplatin resistance. We revealed that PCBP4 combined with Cdc25A and suppressed the expression of Cdc25A, resulting in G2/M arrest. PCBP4 plays important roles in the induction of cisplatin resistance in human maxillary cancers. PCBP4 is a novel molecular target for the therapy of head and neck cancers, especially cisplatin-resistant cancers.

Mutational dichotomy in desmoplastic malignant melanoma corroborated by multigene panel analysis

Desmoplastic malignant melanoma is a distinct melanoma entity histologically subtyped into mixed and pure forms due to significantly reduced lymph node metastases in the pure form. Recent reports investigating common actionable driver mutations have demonstrated a lack of BRAF, NRAS, and KIT mutation in pure desmoplastic melanoma. In search for alternative driver mutations next generation amplicon sequencing for hotspot mutations in 50 genes cardinal to tumorigenesis was performed and in addition the RET G691S polymorphism was investigated. Data from 21 desmoplastic melanomas (12 pure and 9 mixed) were retrieved. Pure desmoplastic melanomas were either devoid of mutations (50%) or displayed mutations in tumor suppressor genes (TP53, CDKN2A, and SMAD4) singularly or in combination with the exception of a PIK3CA double-mutation lacking established biological relevance. Mixed desmoplastic melanomas on the contrary were frequently mutated (89%), and 67% exhibited activating mutations similar to common-type cutaneous malignant melanomas (BRAF, NRAS, FGFR2, and ERBB2). Separate analysis of morphologically heterogeneous tumor areas in four mixed desmoplastic malignant melanomas displayed no difference in mutation status and RET G691 status. GNAQ and GNA11, two oncogenes in BRAF and NRAS wild-type uveal melanomas, were not mutated in our cohort. The RET G691S polymorphism was found in 25% of pure and 38% of mixed desmoplastic melanomas. Apart from RET G691S our findings demonstrate absence of activating driver mutations in pure desmoplastic melanoma beyond previously investigated oncogenes (BRAF, NRAS, and KIT). The findings underline the therapeutic dichotomy of mixed versus pure desmoplastic melanoma with regard to activating mutations primarily of the mitogen-activated protein kinase pathway.

Proteomic Identification of DNA-PK Involvement within the RET Signaling Pathway

Constitutive activation of the Rearranged during Transfection (RET) proto-oncogene leads to the development of MEN2A medullary thyroid cancer (MTC). The relatively clear genotype/phenotype relationship seen with RET mutations and the development of MEN2A is unusual in the fact that a single gene activity can drive the progression towards metastatic disease. Despite knowing the oncogene responsible for MEN2A, MTC, like most tumors of neural crest origin, remains largely resistant to chemotherapy. Constitutive activation of RET in a SK-N-MC cell line model reduces cell sensitivity to chemotherapy. In an attempt to identify components of the machinery responsible for the observed RET induced chemoresistance, we performed a proteomic screen of histones and associated proteins in cells with a constitutively active RET signaling pathway. The proteomic approach identified DNA-PKcs, a DNA damage response protein, as a target of the RET signaling pathway. Active DNA-PKcs, which is phosphorylated at site serine 2056 and localized to chromatin, was elevated within our model. Treatment with the RET inhibitor RPI-1 significantly reduced s2056 phosphorylation in RET cells as well as in a human medullary thyroid cancer cell line. Additionally, inhibition of DNA-PKcs activity diminished the chemoresistance observed in both cell lines. Importantly, we show that activated DNA-PKcs is elevated in medullary thyroid tumor samples and that expression correlates with expression of RET in thyroid tumors. These results highlight one mechanism by which RET signaling likely primes cells for rapid response to DNA damage and suggests DNA-PKcs as an additional target in MTC.

Neurotrophin receptors and perineural invasion in desmoplastic melanoma

BACKGROUND

Perineural invasion (PNI) in desmoplastic melanoma is associated with increased local recurrence and reduced disease-free survival. The biological mechanisms underlying PNI remain unclear although several lines of evidence implicate neurotrophins and their receptors.

OBJECTIVES

We investigated the expression of p75NGFR and TrkA, and the presence of functional RET polymorphism (RETp) as they relate to PNI in desmoplastic melanoma.

METHODS

In all, 43 cases of desmoplastic melanoma were immunohistochemically evaluated for TrkA and p75NGFR expression and RETp was detected by direct DNA sequencing.

RESULTS

PNI was present in 67% of cases. On univariate analysis, p75NGFR was associated with PNI (expression detected in 79% of PNI-positive cases compared with 36% of PNI-negative cases, P = .005), increased Breslow depth (P = .007), and greater Clark level (P = .01). RETp was noted in 28% of cases but was not significantly associated with PNI (P = .27) or other histopathologic variables. TrkA expression was absent in all cases. PNI was associated with increased Breslow depth and Clark level (P = .01 and P = .009, respectively). Controlling for the association between p75NGFR and depth, p75NGFR remained associated with an increased propensity for PNI (odds ratio 4.68, P = .04).

LIMITATIONS

The sample size was limited.

CONCLUSION

In desmoplastic melanoma, p75NGFR expression is significantly associated with PNI and a more locally aggressive phenotype.

The modifier role of RET-G691S polymorphism in hereditary medullary thyroid carcinoma: functional characterization and expression/penetrance studies

Background

Hereditary medullary thyroid carcinoma (MTC) is caused by germ-line gain of function mutations in the RET proto-oncogene, and a phenotypic variability among carriers of the same mutation has been reported. We recently observed this phenomenon in a large familial MTC (FMTC) family carrying the RET-S891A mutation. Among genetic modifiers affecting RET-driven MTC, a role has been hypothesized for RET-G691S non-synonymous polymorphism, though the issue remains controversial. Aim of this study was to define the in vitro contribution of RET-G691S to the oncogenic potential of the RET-S891A, previously shown to harbour low transforming activity.

Methods

The RET-S891A and RET-G691S/S891A mutants were generated by site-directed mutagenesis, transiently transfected in HEK293T cells and stably expressed in NIH3T3 cells. Their oncogenic potential was defined by assessing the migration ability by wound healing assay and the anchorage-independent growth by soft agar assay in NIH3T3 cells stably expressing either the single or the double mutants. Two RET-S891A families were characterised for the presence of RET-G691S.

Results

The functional studies demonstrated that RET-G691S/S891A double mutant displays a higher oncogenic potential than RET-S891A single mutant, assessed by focus formation and migration ability. Moreover, among the 25 RET-S891A carriers, a trend towards an earlier age of diagnosis was found in the MTC patients harboring RET-S891A in association with RET-G691S.

Conclusions

We demonstrate that the RET-G691S non-synonymous polymorphism enhances in vitro the oncogenic activity of RET-S891A. Moreover, an effect on the phenotype was observed in the RET-G691S/S891A patients, thus suggesting that the analysis of this polymorphism could contribute to the decision on the more appropriate clinical and follow-up management.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-015-0231-z) contains supplementary material, which is available to authorized users.

MicroRNA-93 activates c-Met/PI3K/Akt pathway activity in hepatocellular carcinoma by directly inhibiting PTEN and CDKN1A

To assess the role of microRNAs (miR) in hepatocellular carcinoma (HCC), we performed comprehensive microRNA expression profiling using HCC cell lines and identified miR-93 as a novel target associated with HCC. We further verified miR-93 expression levels in advanced HCC tumors (n=47) by a direct PCR assay and found that elevated miR-93 expression level is significantly correlated with poor prognosis. Elevated miR-93 expression significantly stimulated in vitro cell proliferation, migration and invasion, and additionally inhibited apoptosis. We confirmed that miR-93 directly bound with the 3' untranslated regions of the tumor-suppressor genes PTEN and CDKN1A, respectively,and inhibited their expression. As a result of this inhibition, the c-Met/PI3K/Akt pathway activity was enhanced. IHC analysis of HCC tumors showed significant correlation between c-Met protein expression levels and miR-93 expression levels. Knockdown of c-Met inhibited the activation of the c-Met/PI3K/Akt pathway regardless of hepatocyte growth factor (HGF) treatment, and furthermore reduced the expression of miR-93 in these HCC cells. miR-93 also rendered cells to be more sensitive to sorafenib and tivantinib treatment. We concluded that miR-93 stimulated cell proliferation, migration, and invasion through the oncogenic c-Met/PI3K/Akt pathway and also inhibited apoptosis by directly inhibiting PTEN and CDKN1A expression in human HCC.

Kinome sequencing reveals RET G691S polymorphism in human neuroendocrine lung cancer cell lines

Neuroendocrine (NE) lung tumors comprise 20-25% of all invasive lung malignancies. Currently, no effective treatments are available to cure these tumors, and it is necessary to identify a molecular alteration(s) that characterizes NE lung tumor cells. We aimed to identify a kinase mutation(s) associated with NE lung tumor by screening 517 kinase-encoding genes in human lung cancer cell lines. Our next-generation sequencing analysis of six NE lung tumor cell lines (four small cell lung cancer lines and two non-small cell lung cancer lines) and three non-NE lung tumor lines revealed various kinase mutations, including a nonsynonymous mutation in the proto-oncogene RET (c.2071G>A; p.G691S). Further evaluation of the RET polymorphism in total 15 lung cancer cell lines by capillary sequencing suggested that the frequency of the minor allele (A-allele) in NE lung tumor lines was significantly higher than its frequency in a reference population (p = 0.0001). However, no significant difference between non-NE lung tumor lines and a reference group was detected (p = 1.0). Nevertheless, neither RET expression levels were correlated with the levels of neuron-specific enolase (NSE), a key NE marker, nor vandetanib and cabozantinib, small molecule compounds that inhibit RET, affected NSE levels in lung cancer cells. Our data suggest a potential association of G691S RET polymorphism with NE lung tumor, proposing the necessity of more thorough evaluation of this possibility. The dataset of kinase mutation profiles in this report may help choosing cell line models for study of lung cancer.

Molecular pathology of skin neoplasms of the head and neck

CONTEXT

Skin neoplasms include the most common malignancies affecting humans. Many show an ultraviolet (UV)-induced pathogenesis and often affect the head and neck region.

OBJECTIVE

To review literature on cutaneous neoplasms that show a predilection for the head and neck region and that are associated with molecular alterations.

DATA SOURCES

Literature review.

CONCLUSIONS

Common nonmelanoma skin cancers, such as basal and squamous cell carcinomas, show a UV-induced pathogenesis. Basal cell carcinomas are characterized by molecular alterations of the Hedgehog pathway, affecting patched and smoothened genes. While squamous cell carcinomas show UV-induced mutations in several genes, driver mutations are only beginning to be identified. In addition, certain adnexal neoplasms also predominantly affect the head and neck region and show interesting, recently discovered molecular abnormalities, or are associated with hereditary conditions whose molecular genetic pathogenesis is well understood. Furthermore, recent advances have led to an increased understanding of the molecular pathogenesis of melanoma. Certain melanoma subtypes, such as lentigo maligna melanoma and desmoplastic melanoma, which are more often seen on the chronically sun-damaged skin of the head and neck, show differences in their molecular signature when compared to the other more common subtypes, such as superficial spreading melanoma, which are more prone to occur at sites with acute intermittent sun damage. In summary, molecular alterations in cutaneous neoplasms of the head and neck are often related to UV exposure. Their molecular footprint often reflects the histologic tumor type, and familiarity with these changes will be increasingly necessary for diagnostic and therapeutic considerations.

Selective activity over a constitutively active RET-variant of the oral multikinase inhibitor dovitinib: results of the CNIO-BR002 phase I-trial

BACKGROUND

Given our preclinical data showing synergy between dovitinib and paclitaxel in preclinical models we conducted this phase I trial aiming to define the recommended phase II-dose (RP2D) on the basis of toxicity and pharmacodynamic criteria while searching for genetic variants that could sensitize patients to the regimen under study.

PATIENTS AND METHODS

A 3+3 escalation schedule was adopted. Seriated FGF23 and dovitinib and paclitaxel pharmacokinetic profiles were determined along a single-agent dovitinib "priming-phase" followed by a dovitinib + paclitaxel combination phase. RECIST 1.1 criteria and NCI CTCAE V.4.0 were used. In fresh pre-treatment tumor biopsy samples, FGFR1, 2 and 3 amplifications were revealed by FISH probes; 32 missense variants were genotyped in tumors and peripheral blood mononuclear cells with Taqman genotyping assays (FGFR1-3 and RET). Constructs encoding for wild-type and variant genes associated with clinical benefit were transfected into HEK-293 cells for preclinical experiments checking constitutive activation and dovitinib sensitivity of the variants.

RESULTS

twelve patients were recruited in three dose-levels. At level 1B (200 mg dovitinib 5-days-on/2-days-off plus 60 mg/m 2-week of paclitaxel) more than 50% FGF23 upregulation was observed and no dose-limiting-toxicities (DLTs) occurred. The most frequent toxicities were asthenia, neutropenia, nausea/vomiting and transaminitis. Two patients with progressive disease prior to trial inclusion achieved prolonged disease stabilization. Both had the germline variant G2071A in the RET gene, which led to constitutive activation of the protein product and Y-905 phosphorylation, both in transfectants and in patients with the alteration. This variant was sensitive to dovitinib; in addition both patients experienced progression upon medication withdrawal.

CONCLUSIONS

Level 1B was the RP2D as it provided adequate pharmacodynamic exposure to dovitinib. The G2071A germline variant act as a genetic modifier that renders different tumors sensitive to dovitinib.

RET revisited: expanding the oncogenic portfolio

The RET receptor tyrosine kinase is crucial for normal development but also contributes to pathologies that reflect both the loss and the gain of RET function. Activation of RET occurs via oncogenic mutations in familial and sporadic cancers - most notably, those of the thyroid and the lung. RET has also recently been implicated in the progression of breast and pancreatic tumours, among others, which makes it an attractive target for small-molecule kinase inhibitors as therapeutics. However, the complex roles of RET in homeostasis and survival of neural lineages and in tumour-associated inflammation might also suggest potential long-term pitfalls of broadly targeting RET.

Central role of RET in thyroid cancer

RET (rearranged during transfection) is a receptor tyrosine kinase involved in the development of neural crest derived cell lineages, kidney, and male germ cells. Different human cancers, including papillary and medullary thyroid carcinomas, lung adenocarcinomas, and myeloproliferative disorders display gain-of-function mutations in RET. Accordingly, RET protein has become a promising molecular target for cancer treatment.

Epigenetic regulation of REG1A and chemosensitivity of cutaneous melanoma

Regenerating gene 1A (REG1A) plays an important role in tissue regeneration and in cell proliferation in epithelium origin tumors; however, its role in melanoma has not been explored in details. The objective of this study was to identify whether REG1A is expressed in cutaneous melanoma and if REG1A expression status can predict prognosis in cutaneous melanoma patients with metastasis. We also determined whether epigenetic regulation of the promoter region regulates REG1A expression. AJCC stage III cutaneous melanoma specimens with clinically well annotated stage III lymph node melanoma metastasis tissue microarray were assessed by IHC. MALDI-TOF-mass spectrometry and HM450K array were used to identify REG1A promoter region CpG site methylation. Chemotherapeutic agent response by melanoma cells as related to REG1A protein expression was assessed. Post-surgery melanoma patients followed by adjuvant chemotherapy with high REG1A expression had a significantly better prognosis (disease-specific survival) compared with patients with low REG1A expression (log rank test; p = 0.0013). The demethylating reagent 5-Aza-2'-deoxycytidine activated REG1A promoter region resulting in enhanced REG1A mRNA and protein expression in melanoma cell lines. Promoter region CpG methylation was shown to regulate REG1A expression in melanoma cells. Moreover, melanoma lines with high REG1A mRNA expression were more susceptible to Dacarbazine and Cisplatin, as compared with those with low REG1A mRNA expression. In conclusion, REG1A expression status may be useful as a biomarker in melanoma patients for sensitivity to these chemotherapeutic agents. The epigenetic regulation of the REG1A promoter region may offer a potential therapeutic approach to improve chemotherapy for metastatic melanoma patients.

B7-H3 associated with tumor progression and epigenetic regulatory activity in cutaneous melanoma

B7-H3, a cell surface transmembrane glycoprotein, was assessed for its functional and prognostic role in cutaneous melanoma progression. B7-H3 expression in melanoma cells was shown to be related to specific downstream signal transduction events as well as associated with functional epigenetic activity. B7-H3 expression and prognostic utility was shown by RT-qPCR and IHC analysis on individual melanoma specimens and then verified in clinically annotated melanoma stage III and stage IV metastasis tissue microarrays in a double blind study. B7-H3 mRNA expression was shown to be significantly increased with stage of melanoma(P<0.0001) and significantly associated with melanoma-specific survival(MSS) in both stage III(P<0.0001) and stage IV(P<0.012) melanoma patients. B7-H3 expression was related to migration and invasion; overexpression B7-H3 increased migration and invasion while knockdown of B7-H3 reduced cell migration and invasion. MiR-29c expression was shown to inversely regulate B7-H3 expression. Furthermore, we demonstrated that melanoma B7-H3 expression was correlated to p-STAT3 activity level in melanoma tissues and cell lines. These studies demonstrate that B7-H3 is a significant factor in melanoma progression, and events of metastasis.

RET inhibition: implications in cancer therapy

INTRODUCTION

The RET gene encodes a receptor tyrosine kinase essential for ontogenesis of the enteric nervous system and kidney. Following identification of RET, it was found that somatic rearrangements of this gene, conventionally designated as RET/PTC, are frequently present in papillary thyroid carcinoma. Subsequently, activating germ line point mutations of RET were identified as being responsible for the hereditary medullary thyroid carcinoma syndromes MEN2A, MEN2B and FMTC. RET rearrangements have recently been identified in a small fraction of lung adenocarcinomas.

AREA COVERED

The authors review the current field concerning the RET gene and protein, its involvement in cancer and the preclinical and clinical studies which highlight its role as a potentially important therapeutic target for several cancers.

EXPERT OPINION

Many multitargeted inhibitors which crossreact with RET have been developed and investigated in clinical trials targeting many cancer indications. In particular, VEGFR/PDGFR inhibitors, widely explored as antiangiogenics, have been intensively studied in thyroid carcinoma patients. Notwithstanding the efficacy observed with such agents, their common clinical activity in thyroid carcinoma is of short duration and includes frequent and severe side effects, limiting their therapeutic action. These findings are discussed and the need for improved, more specific RET-targeting drugs is highlighted.

ERG transcriptional networks in primary acute leukemia cells implicate a role for ERG in deregulated kinase signaling

High expression of the E26 transforming sequence related gene (ERG) is associated with poor prognosis in a subgroup of leukemia patients with acute myeloid (AML) and acute T-lymphoblastic leukemia (T-ALL). In a previous study we proposed that ERG overexpression may deregulate several signaling cascades in acute leukemia. Herein, we further expand those studies by identifying a consensus of biological targets in primary blasts of newly diagnosed acute leukemia patients. Our findings of chromatin immunoprecipitation-on-chip of primary samples revealed 48 significantly enriched single genes including DAAM1 and NUMB. Significantly enriched signaling pathways included WNT/β-catenin, p53, and PI3K/AKT with ERG overexpression inducing dephosphorylation of AKT(Ser473) relative to non ERG expressing K562 cells. Cell based ERG overexpression studies also revealed drug resistance to multi-kinase inhibitor, BAY 43-9006 (Sorafenib) and to the tyrosine kinase inhibitor TKI258. Thus in primary leukemic cells, ERG may contribute to the dysregulation of kinase signaling, which results in resistance to kinase inhibitors.

The involvement of the RET variant G691S in medullary thyroid carcinoma enlightened by a meta-analysis study

Medullary thyroid carcinoma (MTC) is a rare tumor, partially explained by mutations in the rearranged during transfection (RET) proto-oncogene. The nonsynonymous RET polymorphism G691S has been reported as associated with MTC, but findings are discordant. We sought to clarify the role of G691S in MTCs through in silico analysis, genetic association in our patients and a meta-analysis with extensive literature revision. Ninety-three Italian patients were compared to 85 healthy individuals. Results were included in a meta-analysis together with 11 case-control association studies identified through PubMed, EMBASE and Web of Science, with a combined sample of 968 cases and 2,115 controls. No association of G691S with MTC was found in our sample; however, we observed an excess of homozygotes for the variant, significantly higher among females. The overall allelic association in the meta-analysis was significant under the fixed-effect model (odds ratio [OR] = 1.22 [95% confidence intervals: 1.06-1.39], p = 0.0049), but borderline under the random effect model (OR = 1.21 [0.99-1.46], p = 0.0575), with a moderate/high heterogeneity (I(2) = 44.6%, p = 0.047). Under the recessive model of transmission, applied to the eight studies with available genotype frequencies, results were significant under both effect models (OR = 2.016 and OR = 2.022, p = 0.0004). No heterogeneity was anymore detectable. In silico analyses on G691S confirmed a change of the phosphorylation pattern that might account for the enhanced signaling transduction previously reported for G691S in several cancers, thus also explaining its overrepresentation in MTCs. The G691S variant allele does increase the risk for MTC, with a recessive mechanism of action, apparently more evident among females.

The RET G691S polymorphism is a germline variant in desmoplastic malignant melanoma

The RET protooncogene was originally identified in 1985. It encodes for a receptor tyrosine kinase. The RET receptor is activated by its ligand glial cell-derived neurotrophic factor. A polymorphism, RETp (G691S), in the intracellular juxtamembrane domain of RET, which enhances signaling by glial cell-derived neurotrophic factor has been described and studied previously in pancreatic cancer, medullary thyroid cancer, the multiple endocrine neoplasia 2 syndromes, and recently in cutaneous malignant melanoma. In particular, it has been shown that desmoplastic melanomas, which have neurotrophic features, have a high frequency of this polymorphism. In previous studies, however, it was not clear whether this was a germline or somatic change. Previous studies on pancreatic cancer indicated that both mechanisms may occur. To clarify this further we examined peripheral blood cell DNA from 30 patients with desmoplastic melanomas and 30 patients with nondesmoplastic melanoma for the RETp. In this study, a germline polymorphism was found in 30% of the patients with desmoplastic melanomas and 21% of the patients with nondesmoplastic melanoma. These findings indicate that the RETp may be a genetic risk factor for the development of desmoplastic melanoma.

Mixed versus pure variants of desmoplastic melanoma: a genetic and immunohistochemical appraisal

Desmoplastic melanoma is subclassified into pure and mixed variants with a higher rate of lymph node metastasis in the latter. Given that reasons for these biological differences are not currently known, we investigated these subtypes with techniques that included genetic and immunohistochemical analyses of 43 cases of desmoplastic melanoma (24 pure, 19 mixed). Direct DNA sequencing was performed on BRAFV600E, RET gene (coding region on exon 11) and KIT (exons 11, 13 and 17). Immunohistochemical stains were performed with antibodies to markers of significance with respect to biological potential of nevomelanocytic proliferations and/or desmoplastic melanoma (Ki-67, CD117, nestin, clusterin, SOX10 and CD271/p75NTR). Polymorphism at the RET coding region (RETp) was noted in 33% of pure (8/24 cases) versus 24% of mixed (4/17 cases); BRAFV600E was absent in all cases of pure (0/24 cases) versus 6% of mixed (1/17 cases); no mutations were found in any of the cases on analyses of exons 11, 13 and 17 of the c-KIT gene (P=NS for all). For immunohistochemical analyses of pure versus mixed: mean percentage of Ki-67 nuclear positivity was 5% (s.d.=5.6) versus 28% (s.d.=12.6, P<0.001); CD117 stained 26% (6/23 cases) versus 78% (14/18 cases, P<0.01); nestin stained 83% (n=19/23 cases) versus 89% (16/18 cases, P=NS); clusterin stained 4% (1/23 cases) versus 6% (1/18 cases, P=NS); SOX10 87% (20/23 cases) versus 94% (17/18 cases, P=NS) and CD271 stained 61% (14/23 cases) versus 67% (12/18 cases, P=NS). Increased CD117 staining in the mixed variant suggests that alterations in the KIT protein may be involved in tumor progression. In addition, the proliferative index of the mixed variant was higher than that of the pure variant.

AIM1 and LINE-1 epigenetic aberrations in tumor and serum relate to melanoma progression and disease outcome

Aberrations in the methylation status of non-coding genomic repeat DNA sequences and specific gene promoter region are important epigenetic events in melanoma progression. Promoter methylation status in LINE-1 and Absent in melanoma-1(AIM1;6q21) associated with melanoma progression and disease outcome was assessed. LINE-1 and AIM1 methylation status was assessed in paraffin-embedded archival tissues(PEAT)(n=133) and melanoma patients’ serum(n=56). LINE-1 U-Index(hypomethylation) and AIM1 were analyzed in microdissected melanoma PEAT sections. The LINE-1 U-Index of melanoma(n=100) was significantly higher than that of normal skin(n=14) and nevi(n=12)(P=0.0004). LINE-1 U-Index level was elevated with increasing AJCC stage(P<0.0001). AIM1 promoter hypermethylation was found in higher frequency(P=0.005) in metastatic melanoma(65%) than in primary melanomas(38%). When analyzed, high LINE-1 U-Index and/or AIM1 methylation in melanomas were associated with disease-free survival(DFS) and overall survival(OS) in Stage I/II patients (P=0.017, 0.027; respectively). In multivariate analysis, melanoma AIM1 methylation status was a significant prognostic factor of OS(P=0.032). Furthermore, serum unmethylated LINE-1 was at higher levels in both stage III(n=20) and stage IV(n=36) patients compared to healthy donors(n=14)(P=0.022). Circulating methylated AIM1 was detected in patients’ serum and was predictive of OS in Stage IV patients (P=0.009). LINE-1 hypomethylation and AIM1 hypermethylation have prognostic utility in both melanoma patients’ tumors and serum.

RAS/RAF/MEK/ERK and PI3K/PTEN/AKT Signaling in Malignant Melanoma Progression and Therapy

Cutaneous malignant melanoma is one of the most serious skin cancers and is highly invasive and markedly resistant to conventional therapy. Melanomagenesis is initially triggered by environmental agents including ultraviolet (UV), which induces genetic/epigenetic alterations in the chromosomes of melanocytes. In human melanomas, the RAS/RAF/MEK/ERK (MAPK) and the PI3K/PTEN/AKT (AKT) signaling pathways are two major signaling pathways and are constitutively activated through genetic alterations. Mutations of RAF, RAS, and PTEN contribute to antiapoptosis, abnormal proliferation, angiogenesis, and invasion for melanoma development and progression. To find better approaches to therapies for patients, understanding these MAPK and AKT signaling mechanisms of melanoma development and progression is important. Here, we review MAPK and AKT signaling networks associated with melanoma development and progression.