Faculty Bibliography

Melanoma cell adhesion molecule (MCAM) is upregulated during melanoma progression, and associated with invasion and metastasis. Little is known about the factors that regulate MCAM expression in vivo. Mutations that upregulate MCAM have not been found, and AKT activating mutations are rare in melanomas. This suggests that an epigenetic factor may be responsible for upregulating MCAM and activating AKT in vivo. Although endothelin-1 and endothelin-3 (ET-1, ET-3) are physiologically relevant factors capable of upregulating MCAM in melanocytic cells, a mechanism of action has never been established. Here we show that pharmacologic inhibition of map kinase kinase (MEK) or phosphoinositol 3 kinase (PI3K) blocks MCAM upregulation by ET-3, implicating MEK and PI3K/Akt kinases in ET-3 regulation of MCAM. Despite the fact that there are cAMP response element binding protein (CREB) sites in the MCAM promoter, suppression of CREB expression by siRNA silencing does not block ET-3 mediated upregulation of MCAM. Rather, ET-3 stimulation of melanocytes promotes Akt phosphorylation at Ser 473, which is suppressed by PI3K inhibition or silencing of Akt, in turn blocking ET-3 upregulation of MCAM. We conclude therefore that ETs upregulate MCAM in an Akt and ERK/MEK-dependent, but CREB-independent manner, providing an understanding for possible pharmacologic intervention in progressing melanoma.

The mammalian RNA-binding protein AUF1 (AU-binding factor 1, also known as heterogeneous nuclear ribonucleoprotein D, hnRNP D) binds to numerous mRNAs and influences their post-transcriptional fate. Given that many AUF1 target mRNAs encode muscle-specific factors, we investigated the function of AUF1 in skeletal muscle differentiation. In mouse C2C12 myocytes, where AUF1 levels rise at the onset of myogenesis and remain elevated throughout myocyte differentiation into myotubes, RIP (RNP immunoprecipitation) analysis indicated that AUF1 binds prominently to Mef2c (myocyte enhancer factor 2c) mRNA, which encodes the key myogenic transcription factor Mef2c. By performing mRNA half-life measurements and polysome distribution analysis, we found that AUF1 associated with the 3' UTR of Mef2c mRNA and promoted Mef2c translation without affecting Mef2c mRNA stability. In addition, AUF1 promoted Mef2c gene transcription via a lesser-known role of AUF1 in transcriptional regulation. Importantly, lowering AUF1 delayed myogenesis, while ectopically restoring Mef2c expression levels partially rescued the impairment of myogenesis seen after reducing AUF1 levels. We propose that Mef2c is a key effector of the myogenesis program promoted by AUF1.

Regulated messenger RNA (mRNA) decay is an essential mechanism that governs proper control of gene expression. In fact, many of the most physiologically potent proteins are encoded by short-lived mRNAs, many of which contain AU-rich elements (AREs) in their 3'-untranslated region (3'-UTR). AREs target mRNAs for post-transcriptional regulation, generally rapid decay, but also stabilization and translation inhibition. AREs control mRNA turnover and translation activities through association with trans-acting RNA-binding proteins that display high affinity for these AU-rich regulatory elements. AU-rich element RNA-binding protein (AUF1), also known as heterogeneous nuclear ribonucleoprotein D (HNRNPD), is an extensively studied AU-rich binding protein (AUBP). AUF1 has been shown to regulate ARE-mRNA turnover, primarily functioning to promote rapid ARE-mRNA degradation. In certain cellular contexts, AUF1 has also been shown to regulate gene expression at the translational and even the transcriptional level. AUF1 comprises a family of four related protein isoforms derived from a common pre-mRNA by differential exon splicing. AUF1 isoforms have been shown to display multiple and distinct functions that include the ability to target ARE-mRNA stability or decay, and transcriptional activation of certain genes that is controlled by their differential subcellular locations, expression levels, and post-translational modifications. AUF1 has been implicated in controlling a variety of physiological functions through its ability to regulate the expression of numerous mRNAs containing 3'-UTR AREs, thereby coordinating functionally related pathways. This review highlights the physiological functions of AUF1-mediated regulation of mRNA and gene expression, and the consequences of deficient AUF1 levels in different physiological settings. For further resources related to this article, please visit the WIREs website. Conflict of interest: The authors have declared no conflicts of interest for this article.

Intra-articular tumors and tumor-like conditions of the hip are rare. When they occur, they can interrupt normal articular congruency, leading to pain and joint dysfunction. If these conditions result in large osteochondral defects, they pose challenging reconstructive problems in young patients. We describe a case of a 29-year-old man who presented with a 2-year history of right hip pain. Advanced imaging demonstrated an expansile lesion in the region of his ligamentum teres (LT), eroding a significant portion of his femoral head and expanding the cotyloid fossa. He was treated with surgical hip dislocation, excision of the lesion, and femoral head reconstruction with fresh osteochondral (OC) allograft transplantation via press-fit technique. Histologic examination of the mass showed a benign fibromyxoid pseudotumor. Although non-neoplastic masses have been described in almost all organ systems, to our knowledge this is the first description of this entity affecting the native hip joint. It is only the second description of using press-fit OC allografting in the femoral head. This case adds to the body of literature defining symptomatic LT pathology that may benefit from surgical management. It underscores the need to study the ligament further, as the ability to diagnose and treat intra-articular hip pathology has improved with modern imaging and methods of open and arthroscopic hip surgery.

INTRODUCTION: Rapamycin acts synergistically with platinum agents to induce apoptosis and inhibit proliferation in breast cancer cell lines. Combination of everolimus also known as RAD001 (oral mammalian target of rapamycin (mTOR) inhibitor) and carboplatin may have activity in metastatic triple-negative breast cancer (TNBC). METHODS: The primary objective of this study was to determine clinical benefit rate (CBR), that is (complete remission (CR) + partial remission (PR) + stable disease (SD) lasting >/=6 months) and the toxicity of everolimus/carboplatin in women with metastatic TNBC. Prior carboplatin was allowed. Treatment consisted of intravenous carboplatin area under the curve (AUC) 6 (later decreased to AUC 5 and subsequently to AUC 4) every 3 weeks with daily 5 mg everolimus. RESULTS: We enrolled 25 patients in this study. Median age was 58 years. There were one CR, six PRs, seven SDs and eight PDs (progression of disease). CBR was 36% (95% confidence interval (CI) 21.1 to 57.4%). One SD was achieved in a patient progressing on single agent carboplatin. The median progression free survival (PFS) was 3 months (95% CI 1.6 to 4.6 months) and overall survival (OS) was 16.6 months (95% CI 7.3 months to not reached). There were seven patients (28%) with >/= grade 3 thrombocytopenia; three (12%) with grade 3 neutropenia (no bleeding/febrile neutropenia) and one (4%) with grade 3 anemia. Greater hematological toxicity was seen in the first seven patients treated with carboplatin AUC5/6. After the amendment for starting dose of carboplatin to AUC 4, the regimen was well tolerated with only one out of 18 patients with grade 3 neutropenia and two patients with grade 3 thrombocytopenia. There was only one case of mucositis. CONCLUSION: Everolimus-carboplatin was efficacious in metastatic TNBC. Dose limiting hematological toxicity was observed when AUC5/6 of carboplatin was combined with everolimus. However, carboplatin AUC 4 was well tolerated in combination with everolimus with continuing responses. TRIAL REGISTRATIONS: ClinicalTrials.gov NCT01127763.

OBJECTIVES: Up to 70% of endometrioid endometrial cancers carry PTEN gene deletions that can upregulate mTOR activity. Investigational mTOR kinase inhibitors may provide a novel therapeutic approach for these tumors. Using a xenograft tumor model of endometrial cancer, we assessed the activity of mTOR and downstream effector proteins in the mTOR translational control pathway after treatment with a dual mTOR complex 1 and 2 (mTORC1/2) catalytic inhibitor (PP242) compared to that of an allosteric mTOR complex 1 (mTORC1) inhibitor (everolimus, RAD001). METHODS: Grade 3 endometrioid endometrial cancer cells (AN3CA) were xenografted into nude mice. Animals were treated with PP242, PP242 and carboplatin, carboplatin, RAD001, and RAD001 and carboplatin. Mean tumor volume was compared across groups by ANOVA. Immunoblot analysis was performed to assess mTORC1/2 activity using P-Akt, P-S6 and P-4E-BP1. RESULTS: The mean tumor volume of PP242+carboplatin was significantly lower than in all other treatment groups, P<0.001 (89% smaller). The RAD001+carboplatin group was also smaller, but this did not reach statistical significance (P=0.097). Immunoblot analysis of tumor lysates treated with PP242 demonstrated inhibition of activated P-Akt. CONCLUSIONS: Catalytic mTORC1/2 inhibition demonstrates clear efficacy in tumor growth control that is enhanced by the addition of a DNA damage agent, carboplatin. Targeting mTORC1/2 leads to inhibition of Akt activation and strong downregulation of effectors of mTORC1, resulting in downregulation of protein synthesis. Based on this study, mTORC1/2 kinase inhibitors warrant further investigation as a potential treatment for endometrial cancer.

Although there is a growing literature describing the role of macrophages in breast cancer, the role of macrophages in inflammatory breast cancer (IBC) is unclear. The aim of present study was to isolate and characterize tumor associated macrophages of IBC and non-IBC patients and define their role in IBC. Tumor infiltrating monocytes/macrophages (CD14+ and CD68+) were measured by immunohistochemistry using specific monoclonal antibodies. Blood drained from axillary vein tributaries was collected during breast cancer surgery and the percentage of CD14+ in the total isolated leukocytes was assessed by flow cytometric analysis. CD14+ cells were separated from total leukocytes by immuno-magnetic beads technique and were cultured overnight. Media conditioned by CD14+ were collected and subjected to cytokine profiling using cytokine antibody array. Wound healing and invasion assays were used to test whether cytokines highly secreted by tumor drained macrophages induce motility and invasion of breast cancer cells. We found that macrophages highly infiltrate into carcinoma tissues of IBC patients. In addition blood collected from axillary tributaries of IBC patients is highly enriched with CD14+ cells as compared to blood collected from non-IBC patients. Cytokine profiling of CD14+ cells isolated from IBC patients revealed a significant increase in secretion of tumor necrosis factor-alpha; monocyte chemoattractant protein-1/CC-chemokine ligand 2; interleukin-8 and interleukin-10 as compared to CD14+ cells isolated from non-IBC patients. Tumor necrosis factor-alpha, interleukin-8 and interleukin-10 significantly increased motility and invasion of IBC cells in vitro. In conclusion, macrophages isolated from the tumor microenvironment of IBC patients secrete chemotactic cytokines that may augment dissemination and metastasis of IBC carcinoma cells.