Biological evaluation of [4-(4-aminophenyl)-1-(4-fluorophenyl)-1H-pyrrol-3-yl](3,4,5-trimethoxyphenyl)methanone as potential antineoplastic agent in 2D and 3D breast cancer models

Targeting tubulin polymerization and depolymerization represents a promising approach to treat solid tumors. In this study, we investigated the molecular mechanisms underlying the anticancer effects of a structurally novel tubulin inhibitor, [4-(4-aminophenyl)-1-(4-fluorophenyl)-1H-pyrrol-3-yl](3,4,5-trimethoxyphenyl)methanone (ARDAP), in two- and three-dimensional MCF-7 breast cancer models. At sub-cytotoxic concentrations, ARDAP showed a marked decrease in cell proliferation, colony formation, and ATP intracellular content in MCF-7 cells, by acting through a cytostatic mechanism. Additionally, drug exposure caused blockage of the epithelial-to-mesenchymal transition (EMT). In 3D cell culture, ARDAP negatively affected tumor spheroid growth, with inhibition of spheroid formation and reduction of ATP concentration levels. Notably, ARDAP exposure promoted the differentiation of MCF-7 cells by inducing: (i) expression decrease of Oct4 and Sox2 stemness markers, both in 2D and 3D models, and (ii) downregulation of the stem cell surface marker CD133 in 2D cell cultures. Interestingly, treated MCF7 cells displayed a major sensitivity to cytotoxic effects of the conventional chemotherapeutic drug doxorubicin. In addition, although exhibiting growth inhibitory effects against breast cancer cells, ARDAP showed insignificant harm to MCF10A healthy cells. Collectively, our results highlight the potential of ARDAP to emerge as a new chemotherapeutic agent or adjuvant compound in chemotherapeutic treatments.

Comparative Gene Expression Profiling of Tobacco-Associated HPV-Positive versus Negative Oral Squamous Carcinoma Cell Lines

Background: HPV-positive oral squamous cell carcinomas (OSCCs) are specific biological and clinical entities, characterized by a more favorable prognosis compared to HPV-negative OSCCs and occurring generally in non-smoking and non-drinking younger individuals. However, poor information is available on the molecular and the clinical behavior of HPV-positive oral cancers occurring in smoking/drinking subjects. Thus, this study was designed to compare, at molecular level, two OSCC cell lines, both derived from drinking and smoking individuals and differing for presence/absence of HPV infection. Methods: HPV-negative UPCI-SCC-131 and HPV16-positive UPCI-SCC-154 cell lines were compared by whole genome gene expression profiling and subsequently studied for activation of Wnt/βCatenin signaling pathway by the expression of several Wnt-target genes, βCatenin intracellular localization, stem cell features and miRNA let-7e. Gene expression data were validated in head and neck squamous cell carcinoma (HNSCC) public datasets. Results: Gene expression analysis identified Wnt/βCatenin pathway as the unique signaling pathway more active in HPV-negative compared to HPV-positive OSCC cells and this observation was confirmed upon evaluation of several Wnt-target genes (i.e., Cyclin D1, Cdh1, Cdkn2a, Cd44, Axin2, c-Myc and Tcf1). Interestingly, HPV-negative OSCC cells showed higher levels of total βCatenin and its active form, increase of its nuclear accumulation and more prominent stem cell traits. Furthermore, miRNA let-7e was identified as potential upstream regulator responsible for the downregulation of Wnt/βCatenin signaling cascade since its silencing in UPCI-SCC-154 cell resulted in upregulation of Wnt-target genes. Finally, the analysis of two independent gene expression public datasets of human HNSCC cell lines and tumors confirmed that Wnt/βCatenin pathway is more active in HPV-negative compared to HPV-positive tumors derived from individuals with smoking habit. Conclusions: These data suggest that lack of HPV infection is associated with more prominent activation of Wnt/βCatenin signaling pathway and gain of stem-like traits in tobacco-related OSCCs.

Heat shock proteins in cancer stem cell maintenance: A potential therapeutic target?

Cancer stem cells (CSCs) are a subpopulation of tumor cells with unlimited self-renewal capability, multilineage differentiation potential and long-term tumor repopulation capacity. CSCs reside in anatomically distinct regions within the tumor microenvironment, called niches, and this favors the maintenance of CSC properties and preserves their phenotypic plasticity. Indeed, CSCs are characterized by a flexible state based on their capacity to interconvert between a differentiated and a stem-like phenotype, and this depends on the activation of adaptive mechanisms in response to different environmental conditions. Heat Shock Proteins (HSPs) are molecular chaperones, upregulated upon cell exposure to several stress conditions and are responsible for normal maturation, localization and activity of intra and extracellular proteins. Noteworthy, HSPs play a central role in several cellular processes involved in tumor initiation and progression (i.e. cell viability, resistance to apoptosis, stress conditions and drug therapy, EMT, bioenergetics, invasiveness, metastasis formation) and, thus, are widely considered potential molecular targets. Furthermore, much evidence suggests a key regulatory function for HSPs in CSC maintenance and their upregulation has been proposed as a mechanism used by CSCs to adapt to unfavorable environmental conditions, such as nutrient deprivation, hypoxia, inflammation. This review discusses the relevance of HSPs in CSC biology, highlighting their role as novel potential molecular targets to develop anticancer strategies aimed at CSC targeting.

Endoplasmic Reticulum Stress and Unfolded Protein Response in Breast Cancer: The Balance between Apoptosis and Autophagy and Its Role in Drug Resistance

The unfolded protein response (UPR) is a stress response activated by the accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum (ER) and its uncontrolled activation is mechanistically responsible for several human pathologies, including metabolic, neurodegenerative, and inflammatory diseases, and cancer. Indeed, ER stress and the downstream UPR activation lead to changes in the levels and activities of key regulators of cell survival and autophagy and this is physiologically finalized to restore metabolic homeostasis with the integration of pro-death or/and pro-survival signals. By contrast, the chronic activation of UPR in cancer cells is widely considered a mechanism of tumor progression. In this review, we focus on the relationship between ER stress, apoptosis, and autophagy in human breast cancer and the interplay between the activation of UPR and resistance to anticancer therapies with the aim to disclose novel therapeutic scenarios. The hypothesis that autophagy and UPR may provide novel molecular targets in human malignancies is discussed.

IL6/STAT3 axis mediates resistance to BRAF inhibitors in thyroid carcinoma cells

Thyroid carcinomas (TCs) bearing BRAF mutations represent approximately 26-53% of human thyroid malignancies and, differently from melanomas, are poorly sensitive to BRAF inhibitors (BRAFi), and develop acquired resistance through activation of alternative signaling pathways. A whole-genome gene expression analysis of TC BRAF V600E cells exposed to PLX4032 identified JAK/STAT among the most significantly modulated signaling pathways. Interestingly, both transient exposure and chronic adaptation to PLX4032 resulted in upregulation of IL6/STAT3 axis and this impaired the cytostatic activity of PLX4032. Mechanistically, exposure to PLX4032 enhanced IL6 secretion and this, in turn, was responsible for STAT3 upregulation, activation of ERK signaling and poor sensitivity to BRAF inhibition. Consistently, the dual blockade of STAT3 (by siRNA or pharmacological inhibition) or IL6 signaling (by the humanized anti-human IL6 receptor antibody, tocilizumab) and BRAF (by PLX4032) improved the inhibition of cell cycle progression compared to PLX4032 single agent. These data support the role of IL6/STAT3 signaling pathway in modulating TC cell response to PLX4032 and candidate IL6 targeting as a strategy to improve the activity of PLX4032 in BRAF V600E TC cells.

Cyclin-dependent kinase 1 targeting improves sensitivity to radiation in BRAF V600E colorectal carcinoma cells

OBJECTIVES

Preoperative chemoradiation is currently the standard of care in locally advanced rectal carcinoma, even though a subset of rectal tumors does not achieve major clinically meaningful responses upon neoadjuvant chemoradiation. At present, no molecular biomarkers are available to predict response to neoadjuvant chemoradiation and select resistant tumors willing more intense therapeutic strategies. Thus, BRAF mutational status was investigated for its role in favoring resistance to radiation in colorectal carcinoma cell lines and cyclin-dependent kinase 1 as a target to improve radiosensitivity in BRAF V600E colorectal tumor cells.

METHODS

Colony-forming assay and apoptotic rates were evaluated to compare the sensitivity of different colon carcinoma cell lines to ionizing radiation and their radiosensitivity upon exposure to BRAF and/or cyclin-dependent kinase 1 inhibitory/silencing strategies. Cyclin-dependent kinase 1 expression/subcellular distribution was studied by immunoblot analysis.

RESULTS

Colon carcinoma BRAF V600E HT29 cells exhibited poor response to radiation compared to BRAF wild-type COLO320 and HCT116 cells. Interestingly, neither radiosensitizing doses of 5-fluoruracil nor BRAF inhibition/silencing significantly improved radiosensitivity in HT29 cells. Of note, poor response to radiation correlated with upregulation/relocation of cyclin-dependent kinase 1 in mitochondria. Consistently, cyclin-dependent kinase 1 inhibition/silencing as well as its targeting, through inhibition of HSP90 quality control pathway, significantly inhibited the clonogenic ability and increased apoptotic rates in HT29 cells upon exposure to radiation.

CONCLUSION

These data suggest that BRAF V600E colorectal carcinoma cells are poorly responsive to radiation, and cyclin-dependent kinase 1 represents a target to improve radiosensitivity in BRAF V600E colorectal tumor cells.

TRAP1 protein signature predicts outcome in human metastatic colorectal carcinoma

TRAP1 is a HSP90 molecular chaperone upregulated in colorectal carcinomas and involved in control of intracellular signaling, cell cycle, apoptosis and drug resistance, stemness and bioenergetics through co-traslational regulation of a network of client proteins. Thus, the clinical significance of TRAP1 protein network was analyzed in human colorectal cancers. TRAP1 and/or its client proteins were quantified, by immunoblot analysis, in 60 surgical specimens of colorectal carcinomas at different stages and, by immunohistochemistry, in 9 colorectal adenomatous polyps, 11 in situ carcinomas and 55 metastatic colorectal tumors. TRAP1 is upregulated at the transition between low- and high-grade adenomas, in in situ carcinomas and in about 60% of human colorectal carcinomas, being downregulated only in a small cohort of tumors. The analysis of TCGA database showed that a subgroup of colorectal tumors is characterized by gain/loss of TRAP1 copy number, this correlating with its mRNA and protein expression. Interestingly, TRAP1 is co-expressed with the majority of its client proteins and hierarchical cluster analysis showed that the upregulation of TRAP1 and associated 6-protein signature (i.e., IF2α, eF1A, TBP7, MAD2, CDK1 and βCatenin) identifies a cohort of metastatic colorectal carcinomas with a significantly shorter overall survival (HR 5.4; 95% C.I. 1.1-26.6; p=0.037). Consistently, the prognostic relevance of TRAP1 was confirmed in a cohort of 55 metastatic colorectal tumors. Finally, TRAP1 positive expression and its prognostic value are more evident in left colon cancers. These data suggest that TRAP1 protein network may provide a prognostic signature in human metastatic colorectal carcinomas.

Dual EGFR and BRAF blockade overcomes resistance to vemurafenib in BRAF mutated thyroid carcinoma cells

BACKGROUND

BRAF inhibitors are effective anticancer agents in BRAF-mutated melanomas. By contrast, evidences about sensitivity of thyroid carcinomas to BRAF inhibition are conflicting and it has been proposed that BRAF V600E thyroid carcinoma cells are less sensitive to BRAF inhibitors due to activation of parallel signaling pathways. This study evaluated the hypothesis that feedback activation of EGFR signaling counteracts the cytostatic activity of vemurafenib (PLX4032) in BRAF V600E thyroid carcinoma cells.

METHODS

Cell proliferation, cell cycle distribution, induction of apoptosis and EGFR and AKT signaling were evaluated in thyroid carcinoma cell lines bearing the BRAF V600E mutation in response to PLX4032.

RESULTS

A partial and transient cytostatic response to PLX4032 was observed in thyroid carcinoma cell lines bearing the BRAF V600E mutation, with lack of full inhibition of ERK pathway. Interestingly, the exposure of thyroid carcinoma cells to PLX4032 resulted in a rapid feedback activation of EGFR signaling with parallel activation of AKT phosphorylation. Consistently, the dual inhibition of EGFR and BRAF, through combination therapy with PLX4032 and gefitinib, resulted in prevention of EGFR phosphorylation and sustained inhibition of ERK and AKT signaling and cell proliferation. Of note, the combined treatment with gefitinib and vemurafenib or the exposure of EGFR-silenced thyroid carcinoma cells to vemurafenib induced synthetic lethality compared to single agents.

CONCLUSIONS

These data suggest that the dual EGFR and BRAF blockade represents a strategy to by-pass resistance to BRAF inhibitors in thyroid carcinoma cells.

TRAP1 controls cell cycle G2-M transition through the regulation of CDK1 and MAD2 expression/ubiquitination

Regulation of tumour cell proliferation by molecular chaperones is still a complex issue. Here, the role of the HSP90 molecular chaperone TRAP1 in cell cycle regulation was investigated in a wide range of human breast, colorectal, and lung carcinoma cell lines, and tumour specimens. TRAP1 modulates the expression and/or the ubiquitination of key cell cycle regulators through a dual mechanism: (i) transcriptional regulation of CDK1, CYCLIN B1, and MAD2, as suggested by gene expression profiling of TRAP1-silenced breast carcinoma cells; and (ii) post-transcriptional quality control of CDK1 and MAD2, being the ubiquitination of these two proteins enhanced upon TRAP1 down-regulation. Mechanistically, TRAP1 quality control on CDK1 is crucial for its regulation of mitotic entry, since TRAP1 interacts with CDK1 and prevents CDK1 ubiquitination in cooperation with the proteasome regulatory particle TBP7, this representing the limiting factor in TRAP1 regulation of the G2-M transition. Indeed, TRAP1 silencing results in enhanced CDK1 ubiquitination, lack of nuclear translocation of CDK1/cyclin B1 complex, and increased MAD2 degradation, whereas CDK1 forced up-regulation partially rescues low cyclin B1 and MAD2 levels and G2-M transit in a TRAP1-poor background. Consistently, the CDK1 inhibitor RO-3306 is less active in a TRAP1-high background. Finally, a significant correlation was observed between TRAP1 and Ki67, CDK1 and/or MAD2 expression in breast, colorectal, and lung human tumour specimens. This study represents the first evidence that TRAP1 is relevant in the control of the complex machinery that governs cell cycle progression and mitotic entry and provides a strong rationale to regard TRAP1 as a biomarker to select tumours with deregulated cell cycle progression and thus likely poorly responsive to novel cell cycle inhibitors. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

TRAP1: a viable therapeutic target for future cancer treatments?

INTRODUCTION

HSP90 molecular chaperones (i.e., HSP90α, HSP90β, GRP94 and TRAP1) are potential therapeutic targets to design novel anticancer agents. However, despite numerous designed HSP90 inhibitors, most of them have failed due to unfavorable toxicity profiles and lack of specificity toward different HSP90 paralogs. Indeed, a major limitation in this field is the high structural homology between different HSP90 chaperones, which significantly limits our capacity to design paralog-specific inhibitors. Area covered: This review examines the relevance of TRAP1 in tumor development and progression, with an emphasis on its oncogenic/oncosuppressive role in specific human malignancies and its multifaceted and context-dependent functions in cancer cells. Herein, we discuss the rationale for considering TRAP1 as a potential molecular target and the strategies used to date, to achieve its compartmentalized inhibition directly in mitochondria. Expert opinion: TRAP1 targeting may represent a promising strategy for cancer therapy, based on the increasing and compelling evidence supporting TRAP1 involvement in human carcinogenesis. However, considering the complexity of TRAP1 biology, future strategies of drug discovery need to improve selectivity and specificity toward TRAP1 respect to other HSP90 paralogs. The characterization of specific human malignancies suitable for TRAP1 targeting is also mandatory.

TRAP1 downregulation in human ovarian cancer enhances invasion and epithelial-mesenchymal transition

Ovarian cancer (OC) is the second leading cause of gynecological cancer death worldwide. Although the list of biomarkers is still growing, molecular mechanisms involved in OC development and progression remain elusive. We recently demonstrated that lower expression of the molecular chaperone TRAP1 in OC patients correlates with higher tumor grade and stage, and platinum resistance. Herein we show that TRAP1 is often deleted in high-grade serous OC patients (N=579), and that TRAP1 expression is correlated with the copy number, suggesting this could be one of the driving mechanisms for the loss of TRAP1 expression in OC. At molecular level, downregulation of TRAP1 associates with higher expression of p70S6K, a kinase frequently active in OC with emerging roles in cell migration and tumor metastasis. Indeed, TRAP1 silencing in different OC cells induces upregulation of p70S6K expression and activity, enhancement of cell motility and epithelial-mesenchymal transition (EMT). Consistently, in a large cohort of OC patients, TRAP1 expression is reduced in tumor metastases and directly correlates with the epithelial marker E-Cadherin, whereas it inversely correlates with the transcription factor Slug and the matrix metallopeptidases 2 and 9. Strikingly, pharmacological inhibition of p70S6K reverts the high motility phenotype of TRAP1 knock-down cells. However, although p70S6K inhibition or silencing reduces the expression of the transcription factors Snail and Slug, thus inducing upregulation of E-Cadherin expression, it is unable to revert EMT induced by TRAP1 silencing; furthermore, p70S6K did not show any significant correlation with EMT genes in patients, nor with overall survival or tumor stage, suggesting an independent and predominant role for TRAP1 in OC progression. Altogether, these results may provide novel approaches in OC with reduced TRAP1 expression, which could be resistant to therapeutic strategies based on the inhibition of the p70S6K pathway, with potential future intervention in OC invasion and metastasis.

New Inhibitors of Indoleamine 2,3-Dioxygenase 1: Molecular Modeling Studies, Synthesis, and Biological Evaluation

Indoleamine 2,3-dioxygenase 1 (IDO1) is an attractive target for anticancer therapy. Herein, we report a virtual screening study which led to the identification of compound 5 as a new IDO1 inhibitor. In order to improve the biological activity of the identified hit, arylthioindoles 6-30 were synthesized and tested. Among these, derivative 21 exhibited an IC₅₀ value of 7 μM, being the most active compound of the series. Furthermore, compounds 5 and 21 induced a dose-dependent growth inhibition in IDO1 expressing cancer cell lines HTC116 and HT29. Three-dimensional quantitative structure-activity relationship studies were carried out in order to rationalize obtained results and suggest new chemical modifications.

TRAP1 regulates stemness through Wnt/β-catenin pathway in human colorectal carcinoma

Colorectal carcinoma (CRC) is a common cause of cancer-related death worldwide. Indeed, treatment failures are triggered by cancer stem cells (CSCs) that give rise to tumor repopulation upon initial remission. Thus, the role of the heat shock protein TRAP1 in stemness was investigated in CRC cell lines and human specimens, based on its involvement in colorectal carcinogenesis, through regulation of apoptosis, protein homeostasis and bioenergetics. Strikingly, co-expression between TRAP1 and stem cell markers was observed in stem cells located at the bottom of intestinal crypts and in CSCs sorted from CRC cell lines. Noteworthy, TRAP1 knockdown reduced the expression of stem cell markers and impaired colony formation, being the CSC phenotype and the anchorage-independent growth conserved in TRAP1-rich cancer cells. Consistently, the gene expression profiling of HCT116 cells showed that TRAP1 silencing results in the loss of the stem-like signature with acquisition of a more-differentiated phenotype and the downregulation of genes encoding for activating ligands and target proteins of Wnt/β-catenin pathway. Mechanistically, TRAP1 maintenance of stemness is mediated by the regulation of Wnt/β-catenin signaling, through the modulation of the expression of frizzled receptor ligands and the control of β-catenin ubiquitination/phosphorylation. Remarkably, TRAP1 is associated with higher expression of β-catenin and several Wnt/β-catenin target genes in human CRCs, thus supporting the relevance of TRAP1 regulation of β-catenin in human pathology. This study is the first demonstration that TRAP1 regulates stemness and Wnt/β-catenin pathway in CRC and provides novel landmarks in cancer biology and therapeutics.

TRAP1 regulates cell cycle and apoptosis in thyroid carcinoma cells

Tumor necrosis factor receptor-associated protein 1 (TRAP1) is a heat shock protein 90 (HSP90) molecular chaperone upregulated in several human malignancies and involved in protection from apoptosis and drug resistance, cell cycle progression, cell metabolism and quality control of specific client proteins. TRAP1 role in thyroid carcinoma (TC), still unaddressed at present, was investigated by analyzing its expression in a cohort of 86 human TCs and evaluating its involvement in cancer cell survival and proliferation in vitro Indeed, TRAP1 levels progressively increased from normal peritumoral thyroid gland, to papillary TCs (PTCs), follicular variants of PTCs (FV-PTCs) and poorly differentiated TCs (PDTCs). By contrast, anaplastic thyroid tumors exhibited a dual pattern, the majority being characterized by high TRAP1 levels, while a small subgroup completely negative. Consistently with a potential involvement of TRAP1 in thyroid carcinogenesis, TRAP1 silencing resulted in increased sensitivity to paclitaxel-induced apoptosis, inhibition of cell cycle progression and attenuation of ERK signaling. Noteworthy, the inhibition of TRAP1 ATPase activity by pharmacological agents resulted in attenuation of cell proliferation, inhibition of ERK signaling and reversion of drug resistance. These data suggest that TRAP1 inhibition may be regarded as potential strategy to target specific features of human TCs, i.e., cell proliferation and resistance to apoptosis.

TRAP1 controls cell migration of cancer cells in metabolic stress conditions: Correlations with AKT/p70S6K pathways

Cell motility is a highly dynamic phenomenon that is essential to physiological processes such as morphogenesis, wound healing and immune response, but also involved in pathological conditions such as metastatic dissemination of cancers. The involvement of the molecular chaperone TRAP1 in the regulation of cell motility, although still controversial, has been recently investigated along with some well-characterized roles in cancer cell survival and drug resistance in several tumour types. Among different functions, TRAP1-dependent regulation of protein synthesis seems to be involved in the migratory behaviour of cancer cells and, interestingly, the expression of p70S6K, a kinase responsible for translation initiation, playing a role in cell motility, is regulated by TRAP1. In this study, we demonstrate that TRAP1 silencing enhances cell motility in vitro but compromises the ability of cells to overcome stress conditions, and that this effect is mediated by the AKT/p70S6K pathway. In fact: i) inhibition of p70S6K activity specifically reduces migration in TRAP1 knock-down cells; ii) nutrient deprivation affects p70S6K activity thereby impairing cell migration only in TRAP1-deficient cells; iii) TRAP1 regulates the expression of both AKT and p70S6K at post-transcriptional level; and iii) TRAP1 silencing modulates the expression of genes involved in cell motility and epithelial-mesenchymal transition. Notably, a correlation between TRAP1 and AKT expression is found in vivo in human colorectal tumours. These results provide new insights into TRAP1 role in the regulation of cell migration in cancer cells, tumour progression and metastatic mechanisms.

Evaluation of Glucose Uptake in Normal and Cancer Cell Lines by Positron Emission Tomography

To date, there is no definitive demonstration of the utility of positron emission tomography (PET) in studying glucose metabolism in cultured cell lines. Thus, this study was designed to compare PET to more standardized methods for the quantitative assessment of glucose uptake in nontransformed and transformed living cells and to validate PET for metabolic studies in vitro. Human colon and breast carcinoma cell lines and mouse embryo fibroblasts were evaluated for [(18)F]fluorodeoxyglucose ([(18)F]FDG) uptake by PET and autoradiography and 2-deoxyglucose (2-DG) incorporation by colorimetric assay and analyzed for the radiotoxic effects of [(18)F]FDG and the expression levels of glucose transporters. Indeed, [(18)F]FDG incorporation on PET was comparable to [(18)F]FDG uptake by autoradiography and 2-DG incorporation by colorimetric assay, although radiotracer-based methods exhibited more pronounced differences between individual cell lines. As expected, these data correlated with glucose transporters 1 to 4 and hexokinase II expression in tumor cell lines and mouse fibroblasts. Notably, [(18)F]FDG incorporation resulted in low apoptotic rates, with fibroblasts being slightly more sensitive to radiotracer-induced cell death. The quantitative analysis of [(18)F]FDG uptake in living cells by PET represents a valuable and reproducible method to study tumor cell metabolism in vitro, being representative of the differences in the molecular profile of normal and tumor cell lines.

The Role of Human Chorionic Gonadotropin as Tumor Marker: Biochemical and Clinical Aspects

Tumor markers are biological substances that are produced/released mainly by malignant tumor cells, enter the circulation in detectable amounts and are potential indicators of the presence of a tumor. The most useful biochemical markers are the tumor-specific molecules, i.e., receptors, enzymes, hormones, growth factors or biological response modifiers that are specifically produced by tumor cells and not, or minimally, by the normal counterpart (Richard et al. Principles and practice of gynecologic oncology. Wolters Kluwer Health, Philadelphia, 2009). Based on their specificity and sensitivity in each malignancy, biomarkers are used for screening, diagnosis, disease monitoring and therapeutic response assessment in clinical management of cancer patients.This chapter is focused on human chorionic gonadotropin (hCG), a hormone with a variety of functions and widely used as a tumor biomarker in selected tumors. Indeed, hCG is expressed by both trophoblastic and non-trophoblastic human malignancies and plays a role in cell transformation, angiogenesis, metastatization, and immune escape, all process central to cancer progression. Of note, hCG testing is crucial for the clinical management of placental trophoblastic malignancies and germ cell tumors of the testis and the ovary. Furthermore, the production of hCG by tumor cells is accompanied by varying degrees of release of the free subunits into the circulation, and this is relevant for the management of cancer patients (Triozzi PL, Stevens VC, Oncol Rep 6(1):7-17, 1999).The name chorionic gonadotropin was conceived: chorion derives from the latin chordate meaning afterbirth, gonadotropin indicates that the hormone is a gonadotropic molecule, acting on the ovaries and promoting steroid production (Cole LA, Int J Endocrinol Metab 9(2):335-352, 2011). The function, the mechanism of action and the interaction between hCG and its receptor continue to be the subject of intensive investigation, even though many issues about hCG have been well documented (Tegoni M et al., J Mol Biol 289(5):1375-1385, 1999).

TRAP1 is involved in BRAF regulation and downstream attenuation of ERK phosphorylation and cell-cycle progression: a novel target for BRAF-mutated colorectal tumors

Human BRAF-driven tumors are aggressive malignancies with poor clinical outcome and lack of sensitivity to therapies. TRAP1 is a HSP90 molecular chaperone deregulated in human tumors and responsible for specific features of cancer cells, i.e., protection from apoptosis, drug resistance, metabolic regulation, and protein quality control/ubiquitination. The hypothesis that TRAP1 plays a regulatory function on the BRAF pathway, arising from the observation that BRAF levels are decreased upon TRAP1 interference, was tested in human breast and colorectal carcinoma in vitro and in vivo. This study shows that TRAP1 is involved in the regulation of BRAF synthesis/ubiquitination, without affecting its stability. Indeed, BRAF synthesis is facilitated in a TRAP1-rich background, whereas increased ubiquitination occurs upon disruption of the TRAP1 network that correlates with decreased protein levels. Remarkably, BRAF downstream pathway is modulated by TRAP1 regulatory activity: indeed, TRAP1 silencing induces (i) ERK phosphorylation attenuation, (ii) cell-cycle inhibition with cell accumulation in G0-G1 and G2-M transitions, and (iii) extensive reprogramming of gene expression. Interestingly, a genome-wide profiling of TRAP1-knockdown cells identified cell growth and cell-cycle regulation as the most significant biofunctions controlled by the TRAP1 network. It is worth noting that TRAP1 regulation on BRAF is conserved in human colorectal carcinomas, with the two proteins being frequently coexpressed. Finally, the dual HSP90/TRAP1 inhibitor HSP990 showed activity against the TRAP1 network and high cytostatic potential in BRAF-mutated colorectal carcinoma cells. Therefore, this novel TRAP1 function represents an attractive therapeutic window to target dependency of BRAF-driven tumors on TRAP1 translational/quality control machinery.

New pyrrole derivatives with potent tubulin polymerization inhibiting activity as anticancer agents including hedgehog-dependent cancer

We synthesized 3-aroyl-1-arylpyrrole (ARAP) derivatives as potential anticancer agents having different substituents at the pendant 1-phenyl ring. Both the 1-phenyl ring and 3-(3,4,5-trimethoxyphenyl)carbonyl moieties were mandatory to achieve potent inhibition of tubulin polymerization, binding of colchicine to tubulin, and cancer cell growth. ARAP 22 showed strong inhibition of the P-glycoprotein-overexpressing NCI-ADR-RES and Messa/Dx5MDR cell lines. Compounds 22 and 27 suppressed in vitro the Hedgehog signaling pathway, strongly reducing luciferase activity in SAG treated NIH3T3 Shh-Light II cells, and inhibited the growth of medulloblastoma D283 cells at nanomolar concentrations. ARAPs 22 and 27 represent a new potent class of tubulin polymerization and cancer cell growth inhibitors with the potential to inhibit the Hedgehog signaling pathway.

TRAP1 revisited: novel localizations and functions of a 'next-generation' biomarker (review)

In the last decade, the identification and characterization of novel molecular mechanisms and pathways involving the heat shock protein TRAP1/HSP75 in cancers and other diseases enhanced the scientific interest. Recent reports have shown that TRAP1 stays at the crossroad of multiple crucial processes in the onset of neoplastic transformation. In fact, TRAP1: i) contributes to the tumor's switch to aerobic glycolysis through the inhibition of succinate dehydrogenase, the complex II of the mitochondrial respiratory chain; ii) is part of a pro-survival signaling pathway aimed at evading the toxic effects of oxidants and anticancer drugs and protects mitochondria against damaging stimuli via a decrease of ROS generation; iii) controls protein homeostasis through a direct involvement in the regulation of protein synthesis and protein co-translational degradation. Therefore, TRAP1 seems to be a central regulatory protein with balancing functions at the intersection of different metabolic processes during the neoplastic transformation. For this reason, it can be considered at the same time an attractive target for the development of novel anticancer strategies and a promising study model to understand the biology of tumor cells at a systemic level. This review summarizes the most recent advances in TRAP1 biology and proposes a new comprehensive view of its functions.

Translational control in the stress adaptive response of cancer cells: a novel role for the heat shock protein TRAP1

TNF receptor-associated protein 1 (TRAP1), the main mitochondrial member of the heat shock protein (HSP) 90 family, is induced in most tumor types and is involved in the regulation of proteostasis in the mitochondria of tumor cells through the control of folding and stability of selective proteins, such as Cyclophilin D and Sorcin. Notably, we have recently demonstrated that TRAP1 also interacts with the regulatory protein particle TBP7 in the endoplasmic reticulum (ER), where it is involved in a further extra-mitochondrial quality control of nuclear-encoded mitochondrial proteins through the regulation of their ubiquitination/degradation. Here we show that TRAP1 is involved in the translational control of cancer cells through an attenuation of global protein synthesis, as evidenced by an inverse correlation between TRAP1 expression and ubiquitination/degradation of nascent stress-protective client proteins. This study demonstrates for the first time that TRAP1 is associated with ribosomes and with several translation factors in colon carcinoma cells and, remarkably, is found co-upregulated with some components of the translational apparatus (eIF4A, eIF4E, eEF1A and eEF1G) in human colorectal cancers, with potential new opportunities for therapeutic intervention in humans. Moreover, TRAP1 regulates the rate of protein synthesis through the eIF2α pathway either under basal conditions or under stress, favoring the activation of GCN2 and PERK kinases, with consequent phosphorylation of eIF2α and attenuation of cap-dependent translation. This enhances the synthesis of selective stress-responsive proteins, such as the transcription factor ATF4 and its downstream effectors BiP/Grp78, and the cystine antiporter system xCT, thereby providing protection against ER stress, oxidative damage and nutrient deprivation. Accordingly, TRAP1 silencing sensitizes cells to apoptosis induced by novel antitumoral drugs that inhibit cap-dependent translation, such as ribavirin or 4EGI-1, and reduces the ability of cells to migrate through the pores of transwell filters. These new findings target the TRAP1 network in the development of novel anti-cancer strategies.

Resistance to paclitxel in breast carcinoma cells requires a quality control of mitochondrial antiapoptotic proteins by TRAP1

TRAP1 is a mitochondrial antiapoptotic protein up-regulated in several human malignancies. However, recent evidences suggest that TRAP1 is also localized in the endoplasmic reticulum (ER) where it is involved in ER stress protection and protein quality control of tumor cells. Based on the mechanistic link between ER stress, protection from apoptosis and drug resistance, we questioned whether these novel roles of TRAP1 are relevant for its antiapoptotic function. Here, we show for the first time that: i) TRAP1 expression is increased in about 50% of human breast carcinomas (BC), and ii) the ER stress protecting activity of TRAP1 is conserved in human tumors since TRAP1 is co-upregulated with the ER stress marker, BiP/Grp78. Notably, ER-associated TRAP1 modulates mitochondrial apoptosis by exerting a quality control on 18 kDa Sorcin, a TRAP1 mitochondrial client protein involved in TRAP1 cytoprotective pathway. Furthermore, this TRAP1 function is relevant in favoring resistance to paclitaxel, a microtubule stabilizing/ER stress inducer agent widely used in BC therapy. Indeed, the transfection of a TRAP1 deletion mutant, whose localization is restricted to the ER, in shTRAP1 cells enhances the expression of mitochondrial Sorcin and protects from apoptosis induced by ER stress agents and paclitaxel. Furthermore, BC cells adapted to paclitaxel or ER stress inducers share common resistance mechanisms: both cell models exhibit cross-resistance to single agents and the inhibition of TRAP1 by siRNAs or gamitrinib, a mitochondria-directed HSP90 family inhibitor, in paclitaxel-resistant cells rescues the sensitivity to paclitaxel. These results support the hypothesis that ER-associated TRAP1 is responsible for an extramitochondrial control of apoptosis and, therefore, an interference of ER stress adaptation through TRAP1 inhibition outside of mitochondria may be considered a further compartment-specific molecular approach to rescue drug-resistance.

Helicobacter pylori acidic stress response factor HP1286 is a YceI homolog with new binding specificity

HP1286 from Helicobacter pylori is among the proteins that play a relevant role in bacterial colonization and persistence in the stomach. Indeed, it was demonstrated to be overexpressed under acidic stress conditions, together with other essential virulence factors. Here we describe its crystal structure, determined at 2.1 A resolution. The molecular model, a dimer characterized by two-fold symmetry, shows that HP1286 structurally belongs to the YceI-like protein family, which in turn is characterized by the lipocalin fold. The latter characterizes proteins possessing an internal cavity with the function of binding and/or transport of amphiphilic molecules. Surprisingly, a molecule of erucamide was found bound in the internal cavity of each monomer of recombinant HP1286, cloned and expressed in an Escherichia coli heterologous system. The shape and length of the cavity indicate that, at variance with other members of the family, HP-YceI has a binding specificity for amphiphilic compounds with a linear chain of about 22 carbon atoms. These features, along with the fact that the protein is secreted by the bacterium and is involved in adaptation to an acidic environment, suggest that its function could be that of sequestering specific fatty acids or amides from the environment, either to supply the bacterium with the fatty acids necessary for its metabolism, or to protect and detoxify it from the detergent-like antimicrobial activity of fatty acids that are eventually present in the external milieu.

HisE11 and HisF8 provide bis-histidyl heme hexa-coordination in the globin domain of Geobacter sulfurreducens globin-coupled sensor

Among heme-based sensors, recent phylogenomic and sequence analyses have identified 34 globin coupled sensors (GCS), to which an aerotactic or gene-regulating function has been tentatively ascribed. Here, the structural and biochemical characterization of the globin domain of the GCS from Geobacter sulfurreducens (GsGCS(162)) is reported. A combination of X-ray crystallography (crystal structure at 1.5 A resolution), UV-vis and resonance Raman spectroscopy reveals the ferric GsGCS(162) as an example of bis-histidyl hexa-coordinated GCS. In contrast to the known hexa-coordinated globins, the distal heme-coordination in ferric GsGCS(162) is provided by a His residue unexpectedly located at the E11 topological site. Furthermore, UV-vis and resonance Raman spectroscopy indicated that ferrous deoxygenated GsGCS(162) is a penta-/hexa-coordinated mixture, and the heme hexa-to-penta-coordination transition does not represent a rate-limiting step for carbonylation kinetics. Lastly, electron paramagnetic resonance indicates that ferrous nitrosylated GsGCS(162) is a penta-coordinated species, where the proximal HisF8-Fe bond is severed.