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Rovida E.,University of Florence | Stecca B.,Core Research Laboratory Istituto Toscano Tumori
Seminars in Cancer Biology | Year: 2015

The Hedgehog-GLI (HH-GLI) signaling is of critical importance during embryonic development, where it regulates a number of cellular processes, including patterning, proliferation and differentiation. Its aberrant activation has been linked to several types of cancer. HH-GLI signaling is triggered by binding of ligands to the transmembrane receptor patched and is subsequently mediated by transcriptional effectors belonging to the GLI family, whose function is fine tuned by a series of molecular interactions and modifications. Several HH-GLI inhibitors have been developed and are in clinical trials. Similarly, the mitogen-activated protein kinases (MAPK) are involved in a number of biological processes and play an important role in many diseases including cancer. Inhibiting molecules targeting MAPK signaling, especially those elicited by the MEK1/2-ERK1/2 pathway, have been developed and are moving into clinical trials. ERK1/2 may be activated as a consequence of aberrant activation of upstream signaling molecules or during development of drug resistance following treatment with kinase inhibitors such as those for PI3K or BRAF. Evidence of a crosstalk between HH-GLI and other oncogenic signaling pathways has been reported in many tumor types, as shown by recent reviews. Here we will focus on the interaction between HH-GLI and the final MAPK effectors ERK1/2, p38 and JNK in cancer in view of its possible implications for cancer therapy. Several reports highlight the existence of a consistent crosstalk between HH signaling and MAPK, especially with the MEK1/2-ERK1/2 pathway, and this fact should be taken into consideration for designing optimal treatment and prevent tumor relapse. © 2015 Elsevier Ltd. Source

Riverso M.,University College London | Riverso M.,Core Research Laboratory Istituto Toscano Tumori | Kortenkamp A.,Brunel University | Silva E.,Brunel University
International Journal of Biochemistry and Cell Biology | Year: 2014

Efforts in understanding the role of the microenvironment in the development of breast cancer have focused on tumor-stroma cross-talk, but the possibility that normal epithelial cells might also play a role in tumor progression has received little attention. Here, we show that non-tumorigenic human mammary epithelial cells (MCF10A and HMEC) secrete factors able to enhance the proliferation of estrogen receptor α (ERα) positive breast cancer cells (MCF7 and T47D) and suppress their ability to undergo apoptosis. Conditioned medium (CM) derived from MCF10A and HMEC cells was capable of activating ERα in a hormone-independent way, by phosphorylating ERα on Ser167. Co-exposure with PI3K and mTORC1 inhibitors significantly reduced the ERα Ser167 phosphorylation and suppressed the proliferation-enhancing effects of both 10A-CM and HMEC-CM on MCF7 cells. We show that MCF10A and HMEC secrete numerous cytokines, among them MCP-1, which was one of the most prevalent. MCP-1 was shown to have a role in the effects elicited by the 10A-CM. It activated the ERα by phosphorylating Ser167 via the PI3K/Akt/mTORC1 signaling pathway, an effect which was further confirmed by silencing the MCP-1 receptors, CCR2 and CCR4. To our knowledge, this is the first time MCP-1 has been shown to contribute to ERα signaling activation. These data suggest that normal mammary cells could have the capability of supporting the proliferation of breast cancer cells via paracrine interactions. A better understanding of the role of these cells may be useful for designing strategies for the prevention of tumor progression at early stages. © 2014 Published by Elsevier Ltd. Source

Luzzatto L.,Scientific Direction | Luzzatto L.,University of Florence | Nannelli C.,Core Research Laboratory Istituto Toscano Tumori | Notaro R.,Core Research Laboratory Istituto Toscano Tumori
Hematology/Oncology Clinics of North America | Year: 2016

G6PD is a housekeeping gene expressed in all cells. Glucose-6-phosphate dehydrogenase (G6PD) is part of the pentose phosphate pathway, and its main physiologic role is to provide NADPH. G6PD deficiency, one of the commonest inherited enzyme abnormalities in humans, arises through one of many possible mutations, most of which reduce the stability of the enzyme and its level as red cells age. G6PD-deficient persons are mostly asymptomatic, but they can develop severe jaundice during the neonatal period and acute hemolytic anemia when they ingest fava beans or when they are exposed to certain infections or drugs. G6PD deficiency is a global health issue. © 2016 Elsevier Inc. Source

Pandolfi S.,Core Research Laboratory Istituto Toscano Tumori | Montagnani V.,Core Research Laboratory Istituto Toscano Tumori | Lapucci A.,University of Florence | Stecca B.,Core Research Laboratory Istituto Toscano Tumori
Cell Death and Differentiation | Year: 2015

HEDGEHOG (HH) signaling is a key regulator of tissue development and its aberrant activation is involved in several cancer types, including melanoma. We and others have shown a reciprocal cross talk between HH signaling and p53, whose function is often impaired in melanoma. Here we present evidence that both GLI1 and GLI2, the final effectors of HH signaling, regulate the transcription factor E2F1 in melanoma cells, by binding to a functional non-canonical GLI consensus sequence. Consistently, we find a significant correlation between E2F1 and PATCHED1 (PTCH1), GLI1 and GLI2 expression in human melanomas. Functionally, we find that E2F1 is a crucial mediator of HH signaling and it is required for melanoma cell proliferation and xenograft growth induced by activation of the HH pathway. Interestingly, we present evidence that the HH/GLI-E2F1 axis positively modulates the inhibitor of apoptosis-stimulating protein of p53 (iASPP) at multiple levels. HH activation induces iASPP expression through E2F1, which directly binds to iASPP promoter. HH pathway also contributes to iASPP function, by the induction of Cyclin B1 and by the E2F1-dependent regulation of CDK1, which are both involved in iASPP activation. Our data show that activation of HH signaling enhances proliferation in presence of E2F1 and promotes apoptosis in its absence or upon CDK1 inhibition, suggesting that E2F1/iASPP dictates the outcome of HH signaling in melanoma. Together, these findings identify a novel HH/GLI-E2F1-iASPP axis that regulates melanoma cell growth and survival, providing an additional mechanism through which HH signaling restrains p53 proapoptotic function. © 2015 Macmillan Publishers Limited All rights reserved. Source

Santini R.,Core Research Laboratory Istituto Toscano Tumori | Pietrobono S.,Core Research Laboratory Istituto Toscano Tumori | Pandolfi S.,Core Research Laboratory Istituto Toscano Tumori | Montagnani V.,Core Research Laboratory Istituto Toscano Tumori | And 5 more authors.
Oncogene | Year: 2014

Melanoma is one of the most aggressive types of human cancer, characterized by enhanced heterogeneity and resistance to conventional therapy at advanced stages. We and others have previously shown that HEDGEHOG-GLI (HH-GLI) signaling is required for melanoma growth and for survival and expansion of melanoma-initiating cells (MICs). Recent reports indicate that HH-GLI signaling regulates a set of genes typically expressed in embryonic stem cells, including SOX2 (sex-determining region Y (SRY)-Box2). Here we address the function of SOX2 in human melanomas and MICs and its interaction with HH-GLI signaling. We find that SOX2 is highly expressed in melanoma stem cells. Knockdown of SOX2 sharply decreases self-renewal in melanoma spheres and in putative melanoma stem cells with high aldehyde dehydrogenase activity (ALDH(high)). Conversely, ectopic expression of SOX2 in melanoma cells enhances their self-renewal in vitro. SOX2 silencing also inhibits cell growth and induces apoptosis in melanoma cells. In addition, depletion of SOX2 progressively abrogates tumor growth and leads to a significant decrease in tumor-initiating capability of ALDH(high) MICs upon xenotransplantation, suggesting that SOX2 is required for tumor initiation and for continuous tumor growth. We show that SOX2 is regulated by HH signaling and that the transcription factors GLI1 and GLI2, the downstream effectors of HH-GLI signaling, bind to the proximal promoter region of SOX2 in primary melanoma cells. In functional studies, we find that SOX2 function is required for HH-induced melanoma cell growth and MIC self-renewal in vitro. Thus SOX2 is a critical factor for self-renewal and tumorigenicity of MICs and an important mediator of HH-GLI signaling in melanoma. These findings could provide the basis for novel therapeutic strategies based on the inhibition of SOX2 for the treatment of a subset of human melanomas. Source

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