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The insulin receptor isoform A (IR-A) plays an increasingly recognized role in fetal growth and tumor biology in response to circulating insulin and/or locally produced IGF2. This role seems not to be shared by the IR isoform B (IR-B). We aimed to dissect the specific impact of IR isoforms in modulating insulin signaling in triple negative breast cancer (TNBC) cells. We generated murine 4T1 TNBC cells deleted from the endogenous insulin receptor (INSR) gene and expressing comparable levels of either human IR-A or IR-B. We then measured IR isoform-specific in vitro and in vivo biological effects and transcriptome in response to insulin. Overall, the IR-A was more potent than the IR-B in mediating cell migration, invasion, and in vivo tumor growth. Transcriptome analysis showed that approximately 89% of insulin-stimulated transcripts depended solely on the expression of the specific isoform. Notably, in cells overexpressing IR-A, insulin strongly induced genes involved in tumor progression and immune evasion including chemokines and genes related to innate immunity. Conversely, in IR-B overexpressing cells, insulin predominantly induced the expression of genes primarily involved in the regulation of metabolic pathways and, to a lesser extent, tumor growth and angiogenesis.

Simple Summary Breast cancer mortality is increased in patients affected by metabolic disorders associated with dysregulation of the Insulin-like growth factor-1 (IGF-1) axis, like obesity and type-2 diabetes. Despite the oncogenic role of this complex signaling system is widely known, the clinical targeting of IGF-1 and its receptor (IGF-1R) has provided valuable benefit only on small sub-populations of cancer patients, thus suggesting that a further characterization of the biological effects of the IGF-1/IGF-1R pathway could pave the way for a better manipulation of this crucial signaling system at the clinical level. In this study, we have identified the protein S100A7 as novel molecular target of IGF-1 action in the breast tumor microenvironment, toward increased cancer-associated angiogenesis. Targeting the IGF-1/IGF-1R/S100A7 pathway may therefore represent a further useful approach for blocking disease progression in breast cancer patients with dysregulated IGF-1 signaling. Abstract Background: Breast cancer (BC) mortality is increased among obese and diabetic patients. Both obesity and diabetes are associated with dysregulation of both the IGF-1R and the RAGE (Receptor for Advanced Glycation End Products) pathways, which contribute to complications of these disorders. The alarmin S100A7, signaling through the receptor RAGE, prompts angiogenesis, inflammation, and BC progression. Methods: We performed bioinformatic analysis of BC gene expression datasets from published studies. We then used Estrogen Receptor (ER)-positive BC cells, CRISPR-mediated IGF-1R KO BC cells, and isogenic S100A7-transduced BC cells to investigate the role of IGF-1/IGF-1R in the regulation of S100A7 expression and tumor angiogenesis. To this aim, we also used gene silencing and pharmacological inhibitors, and we performed gene expression and promoter studies, western blotting analysis, ChIP and ELISA assays, endothelial cell proliferation and tube formation assay. Results: S100A7 expression correlates with worse prognostic outcomes in human BCs. In BC cells, the IGF-1/IGF-1R signaling engages STAT3 activation and its recruitment to the S100A7 promoter toward S100A7 increase. In human vascular endothelial cells, S100A7 activates RAGE signaling and prompts angiogenic effects. Conclusions: In ER-positive BCs the IGF-1 dependent activation of the S100A7/RAGE signaling in adjacent endothelial cells may serve as a previously unidentified angiocrine effector. Targeting S100A7 may pave the way for a better control of BC, particularly in conditions of unopposed activation of the IGF-1/IGF-1R axis.

The development and progression of the great majority of breast cancers (BCs) are mainly dependent on the biological action elicited by estrogens through the classical estrogen receptor (ER), as well as the alternate receptor named G-protein–coupled estrogen receptor (GPER). In addition to estrogens, other hormones and growth factors, including the insulin and insulin-like growth factor system (IIGFs), play a role in BC. IIGFs cooperates with estrogen signaling to generate a multilevel cross-communication that ultimately facilitates the transition toward aggressive and life-threatening BC phenotypes. In this regard, the majority of BC deaths are correlated with the formation of metastatic lesions at distant sites. A thorough scrutiny of the biological and biochemical events orchestrating metastasis formation and dissemination has shown that virtually all cell types within the tumor microenvironment work closely with BC cells to seed cancerous units at distant sites. By establishing an intricate scheme of paracrine interactions that lead to the expression of genes involved in metastasis initiation, progression, and virulence, the cross-talk between BC cells and the surrounding microenvironmental components does dictate tumor fate and patients’ prognosis. Following (i) a description of the main microenvironmental events prompting BC metastases and (ii) a concise overview of estrogen and the IIGFs signaling and their major regulatory functions in BC, here we provide a comprehensive analysis of the most recent findings on the role of these transduction pathways toward metastatic dissemination. In particular, we focused our attention on the main microenvironmental targets of the estrogen-IIGFs interplay, and we recapitulated relevant molecular nodes that orientate shared biological responses fostering the metastatic program. On the basis of available studies, we propose that a functional cross-talk between estrogens and IIGFs, by affecting the BC microenvironment, may contribute to the metastatic process and may be regarded as a novel target for combination therapies aimed at preventing the metastatic evolution.

Target therapy with various kinase inhibitors (KIs) has been extended to patients with advanced thyroid cancer, but only a subset of these compounds has displayed efficacy in clinical use. However, after an initial response to KIs, dramatic disease progression occurs in most cases. With the discovery of cancer stem cells (CSCs), it is possible to postulate that thyroid cancer resistance to KI therapies, both intrinsic and acquired, may be sustained by this cell subtype. Indeed, CSCs have been considered as the main drivers of metastatic activity and therapeutic resistance, because of their ability to generate heterogeneous secondary cell populations and survive treatment by remaining in a quiescent state. Hence, despite the impressive progress in understanding of the molecular basis of thyroid tumorigenesis, drug resistance is still the major challenge in advanced thyroid cancer management. In this view, definition of the role of CSCs in thyroid cancer resistance may be crucial to identifying new therapeutic targets and preventing resistance to anti-cancer treatments and tumor relapse. The aim of this review is to elucidate the possible role of CSCs in the development of resistance of advanced thyroid cancer to current anti-cancer therapies and their potential implications in the management of these patients.

Background Poorly differentiated (PDTC) and anaplastic thyroid (ATC) cancer cells are characterized by the acquisition of epigenetic abnormalities, leading to the silencing of both the sodium iodide co-transporter and the Coxsackie adenovirus receptor. As aberrant histone acetylation and DNA methylation represent epigenetic mechanisms involved in neoplastic transformation, our study investigated the anticancer properties of epigenetic modifiers in thyroid carcinoma. Materials and methods The cytotoxicity and gene expression modulation of histone deacetylase and DNA methyltransferase inhibitors were evaluated in both PDTC and ATC. Results Epigenetic treatments were cytotoxic to tumor thyrocytes and restored sodium iodide co-transporter and Coxsackie adenovirus receptor, expression as well as radioiodine uptake, in PDTC but not in ATC. However, ectopic expression sodium iodide co-transporter re-activated radioiodine incorporation in ATC. Conclusion The ability of epigenetic treatments to interfere with tumor proliferation and induce Coxsackie adenovirus receptor expression, coupled with the ability of ectopic sodium iodide co-transporter to restore radioiodine uptake, raise the possibility that these therapeutic approaches may provide clinical benefit to patients with thyroid carcinoma refractory to radioiodine treatment.

In the last decades increasing importance has been attributed to the Insulin/Insulin-like Growth Factor signaling (IIGFs) in cancer development, progression and resistance to therapy. In fact, IIGFs is often deregulated in cancer. In particular, the mitogenic insulin receptor isoform A (IR-A) and the insulin-like growth factor receptor (IGF-1R) are frequently overexpressed in cancer together with their cognate ligands IGF-1 and IGF-2. Recently, we identified discoidin domain receptor 1 (DDR1) as a new IR-A interacting protein. DDR1, a non-integrin collagen tyrosine kinase receptor, is overexpressed in several malignancies and plays a role in cancer progression and metastasis. Herein, we review recent findings indicating that DDR1 is as a novel modulator of IR and IGF-1R expression and function. DDR1 functionally interacts with IR and IGF-1R and enhances the biological actions of insulin, IGF-1 and IGF-2. Conversely, DDR1 is upregulated by IGF-1, IGF-2 and insulin through the PI3K/AKT/miR-199a-5p circuit. Furthermore, we discuss the role of the non-canonical estrogen receptor GPER1 in the DDR1-IIGFs crosstalk. These data suggest a wider role of DDR1 as a regulator of cell response to hormones, growth factors, and signals coming from the extracellular matrix.

The fetal isoform A of the insulin receptor (IR-A) is frequently overexpressed in a variety of malignancies including breast cancer. IR overexpression has a recognized role in cancer progression and resistance to anticancer therapies. In particular, IR-A has a peculiar mitogenic potential and is activated not only by insulin but also by IGF-2. Previously, we identified discoidin domain receptor 1 (DDR1) as a new IR-A interacting protein. DDR1, a non-integrin collagen tyrosine kinase receptor, is overexpressed in several malignancies and plays a role in cancer progression and metastasis. We now evaluated whether DDR1 is able to exert a role in breast cancer biology by functionally cross-talking with IR. In MCF-7 human breast cancer cells, IR and DDR1 co-immunoprecipitated and co-localized after insulin or IGF-2 stimulation. In a panel of breast cancer cells, DDR1 knockdown by specific siRNAs markedly inhibited IR downstream signaling as well as proliferation, migration and colony formation in response to insulin and IGF-2. These effects were accompanied by reduction of IR protein and mRNA expression, which involved both transcriptional and post-transcriptional effects. DDR1 overexpression elicited opposite effects. Bioinformatics analysis of public domain databases showed that IR and DDR1 co-expression significantly correlates with several clinically relevant histopathological and molecular features of human breast carcinomas. These findings demonstrate that, in human breast cancer cells, DDR1 regulates IR expression and ligand dependent biological actions. This novel functional crosstalk is likely clinically relevant and may become a new molecular target in breast cancer.

Previously published work has demonstrated that overexpression of the insulin receptor isoform A (IR-A) might play a role in cancer progression and metastasis. The IR has a predominant metabolic role in physiology, but the potential role of IR-A in cancer metabolic reprogramming is unknown. We aimed to characterize the metabolic impact of IR-A and its ligand insulin like growth factor 2 (IGF2) in human breast cancer (BC) cells. To establish autocrine IGF2 action, we generated human BC cells MCF7 overexpressing the human IGF2, while we focused on the metabolic effect of IR-A by stably infecting IGF1R-ablated MCF7 (MCF7IGF1R-ve) cells with a human IR-A cDNA. We then evaluated the expression of key metabolism related molecules and measured real-time extracellular acidification rates and oxygen consumption rates using the Seahorse technology. MCF7/IGF2 cells showed increased proliferation and invasion associated with aerobic glycolysis and mitochondrial biogenesis and activity. In MCF7IGF1R-ve/IR-A cells insulin and IGF2 stimulated similar metabolic changes and were equipotent in eliciting proliferative responses, while IGF2 more potently induced invasion. The combined treatment with the glycolysis inhibitor 2-deoxyglucose (2DG) and the mitochondrial inhibitor metformin blocked cell invasion and colony formation with additive effects. Overall, these results indicate that IGF2 and IR-A overexpression may contribute to BC metabolic reprogramming.

The insulin receptor (IR) mediates both metabolic and mitogenic effects especially when overexpressed or in clinical conditions with compensatory hyperinsulinemia, due to the metabolic pathway resistance, as obesity diabetes. In many cancers, IR is overexpressed preferentially as IR-A isoform, derived by alternative splicing of exon 11. The IR-A overexpression, and the increased IR-A:IR-B ratio, are mechanisms that promote the mitogenic response of cancer cells to insulin and IGF-2, which is produced locally by both epithelial and stromal cancer cells. In cancer IR-A, isoform predominance may occur for dysregulation at both mRNA transcription and post-transcription levels, including splicing factors, non-coding RNAs and protein degradation. The mechanisms that regulate IR isoform expression are complex and not fully understood. The IR isoform overexpression may play a role in cancer cell stemness, in tumor progression and in resistance to target therapies. From a clinical point of view, the IR-A overexpression in cancer may be a determinant factor for the resistance to IGF-1R target therapies for this issue. IR isoform expression in cancers may have the meaning of a predictive biomarker and co-targeting IGF-1R and IR-A may represent a new more efficacious treatment strategy.

Patients with thyroid cancers refractory to radioiodine (RAI) treatment show a limited response to various therapeutic options and a low survival rate. The recent use of multikinase inhibitors has also met limited success. An alternative approach relies on drugs that induce cell differentiation, as the ensuing increased expression of the cotransporter for sodium and iodine (NIS) may partially restore sensitivity to radioiodine. The inhibition of the ERK1/2 pathway has shown some efficacy in this context. Aggressive thyroid tumors overexpress the isoform-A of the insulin receptor (IR-A) and its ligand IGF-2; this IGF-2/IR-A loop is associated with de-differentiation and stem-like phenotype, resembling RAI-refractory tumors. Importantly, IR-A has been shown to be positively modulated by the non-integrin collagen receptor DDR1 in human breast cancer. Using undifferentiated human thyroid cancer cells, we now evaluated the effects of DDR1 on IGF-2/IR-A loop and on markers of cell differentiation and stemness. DDR1 silencing or downregulation caused significant reduction of IR-A and IGF-2 expression, and concomitant increased levels of differentiation markers (NIS, Tg, TSH, TPO). Conversely, markers of epithelial-to-mesenchymal transition (Vimentin, Snail-2, Zeb1, Zeb2 and N-Cadherin) and stemness (OCT-4, SOX-2, ABCG2 and Nanog) decreased. These effects were collagen independent. In contrast, overexpression of either DDR1 or its kinase-inactive variant K618A DDR1-induced changes suggestive of less differentiated and stem-like phenotype. Collagen stimulation was uneffective. In conclusion, in poorly differentiated thyroid cancer, DDR1 silencing or downregulation blocks the IGF-2/IR-A autocrine loop and induces cellular differentiation. These results may open novel therapeutic approaches for thyroid cancer.

Thyroid cancer (TC) is the most common endocrine tumor. Although the majority of TCs show good prognoses, a minor proportion are aggressive and refractory to conventional therapies. So far, the molecular mechanisms underlying TC pathogenesis are incompletely understood. Evidence suggests that TC cells and their precursors are responsive to insulin and insulin-like growth factors (IGFs), and often overexpress receptors for insulin (IR) and IGF-1 (IGF-1R). IR exists in two isoforms, namely IR-A and IR-B. The first binds insulin and IGF-2, unlike IR-B, which only binds insulin. IR-A is preferentially expressed in prenatal life and contributes to development through IGF-2 action. Aggressive TC overexpresses IR-A, IGF-2, and IGF-1R. The over-activation of IR-A/IGF-2 loop in TC is associated with stem-like features and refractoriness to some targeted therapies. Importantly, both IR isoforms crosstalk with IGF-1R, giving rise to the formation of hybrids receptors (HR-A or HR-B). Other interactions have been demonstrated with other molecules such as the non-integrin collagen receptor, discoidin domain receptor 1 (DDR1), and the receptor for the hepatocyte growth factor (HGF), Met. These functional networks provide mechanisms for IR signaling diversification, which may also exert a role in TC stem cell biology, thereby contributing to TC initiation and progression. This review focuses on the molecular mechanisms by which deregulated IR isoforms and their crosstalk with other molecules and signaling pathways in TC cells and their precursors may contribute to thyroid carcinogenesis, progression, and resistance to conventional treatments. We also highlight how targeting these alterations starting from TC progenitors cells may represent new therapeutic strategies to improve the clinical management of advanced TCs.

Thyroid cancer (TC) is the most frequent endocrine tumor with a growing incidence worldwide. Besides the improvement of diagnosis, TC increasing incidence is probably due to environmental factors and lifestyle modifications. The actual diagnostic criteria for TC classification are based on fine needle biopsy (FNAB) and histological examination following thyroidectomy. Since in some cases it is not possible to make a proper diagnosis, classical approach needs to be supported by additional biomarkers. Recently, new emphasis has been given to the altered cellular metabolism of proliferating cancer cells which require high amount of glucose for energy production and macromolecules biosynthesis. Also TC displays alteration of energy metabolism orchestrated by oncogenes activation and tumor suppressors inactivation leading to abnormal proliferation. Furthermore, TC shows significant metabolic heterogeneity within the tumor microenvironment and metabolic coupling between cancer and stromal cells. In this review we focus on the current knowledge of metabolic alterations of TC and speculate that targeting TC metabolism may improve current therapeutic protocols for poorly differentiated TC. Future studies will further deepen the actual understandings of the metabolic phenotype of TC cells and will give the chance to provide novel prognostic biomarkers and therapeutic targets in tumors with a more aggressive behavior.

Prostate cancer is the most common cancer in men in many industrialized countries. A role for androgens in prostate tumor progression is well recognized, while estrogens may cooperate with androgens in prostate carcinogenesis. The incidence of prostate cancer is highly variable in the different countries, suggesting an important role of environmental factors. Heavy metals are common environmental contaminants and some of them are confirmed or suspected human carcinogens. Some metals are endowed with estrogenic and/or androgenic activities and may play a role as cancer risk factors through this mechanism. Moreover, prostate cancer may present alterations in the intracellular balance of trace metals, such as zinc and copper, which are involved in several regulatory proteins. Herein, we review the possible role of environmental heavy metals and of metal-dyshomeostasis in prostate cancer development and promotion as well as the potential use of some metals in the prevention and therapy of prostate cancer.

It is now widely accepted that insulin resistance and compensatory hyperinsulinemia are associated to increased cancer incidence and mortality. Moreover, cancer development and progression as well as cancer resistance to traditional anticancer therapies are often linked to a deregulation/overactivation of the insulin-like growth factor (IGF) axis, which involves the autocrine/paracrine production of IGFs (IGF-I and IGF-II) and overexpression of their cognate receptors [IGF-I receptor, IGF-insulin receptor (IR), and IR]. Recently, new drugs targeting various IGF axis components have been developed. However, these drugs have several limitations including the occurrence of insulin resistance and compensatory hyperinsulinemia, which, in turn, may affect cancer cell growth and survival. Therefore, new therapeutic approaches are needed. In this regard, the pleiotropic effects of peroxisome proliferator activated receptor (PPAR)-γ agonists may have promising applications in cancer prevention and therapy. Indeed, activation of PPAR-γ by thiazolidinediones (TZDs) or other agonists may inhibit cell growth and proliferation by lowering circulating insulin and affecting key pathways of the Insulin/IGF axis, such as PI3K/mTOR, MAPK, and GSK3-β/Wnt/β-catenin cascades, which regulate cancer cell survival, cell reprogramming, and differentiation. In light of these evidences, TZDs and other PPAR-γ agonists may be exploited as potential preventive and therapeutic agents in tumors addicted to the activation of IGF axis or occurring in hyperinsulinemic patients. Unfortunately, clinical trials using PPAR-γ agonists as antineoplastic agents have reached conflicting results, possibly because they have not selected tumors with overactivated insulin/IGF-I axis or occurring in hyperinsulinemic patients. In conclusion, the use of PPAR-γ agonists in combined therapies of IGF-driven malignancies looks promising but requires future developments.

Discoidin Domain Receptor 1 (DDR1) is a collagen receptor tyrosine-kinase that contributes to epithelial-to-mesenchymal transition and enhances cancer progression. Our previous data indicate that, in breast cancer cells, DDR1 interacts with IGF-1R and positively modulates IGF-1R expression and biological responses, suggesting that the DDR1-IGF-IR cross-talk may play an important role in cancer. In this study, we set out to evaluate whether IGF-I stimulation may affect DDR1 expression. Indeed, in breast cancer cells (MCF-7 and MDA-MB-231) IGF-I induced significant increase of DDR1 protein expression, in a time and dose dependent manner. However, we did not observe parallel changes in DDR1 mRNA. DDR1 upregulation required the activation of the PI3K/AKT pathway while the ERK1/2, the p70/mTOR and the PKC pathways were not involved. Moreover, we observed that DDR1 protein upregulation was induced by translational mechanisms involving miR-199a-5p suppression through PI3K/AKT activation. This effect was confirmed by both IGF-II produced by cancer-associated fibroblasts from human breast cancer and by stable transfection of breast cancer cells with a human IGF-II expression construct. Transfection with a constitutively active form of AKT was sufficient to decrease miR-199a-5p and upregulate DDR1. Accordingly, IGF-I-induced DDR1 upregulation was inhibited by transfection with pre-miR-199a-5p, which also impaired AKT activation and cell migration and proliferation in response to IGF-I. These results demonstrate that, in breast cancer cells, a novel pathway involving AKT/miR-199a-5p/DDR1 plays a role in modulating IGFs biological responses. Therefore, this signaling pathway may represent an important target for breast cancers with over-activation of the IGF-IR axis.

The Hepatocyte Growth Factor (HGF) and its receptor Met are physiological regulators of cell migration. HGF and Met have also been implicated in tumor progression and metastasis. We show here that the tyrosine kinase inhibitor STI571 has a stimulatory effect on HGF-induced migration and branching morphogenesis in thyroid cancer but not in primary or immortalized thyroid epithelial cells. These stimulatory effects of STI571 are observed at a concentration that is clinically relevant. The STI571-enhanced motile response can be correlated with an increase in the Met receptor tyrosine phosphorylation as well as ERK and Akt activation by HGF. Interestingly, one of the targets of STI571, namely the c-Abl tyrosine kinase, is activated by HGF and is recruited at the migrating edge of thyroid cancer cells. These data suggests that c-Abl and/or STI571-inhibited tyrosine kinases can negatively regulate the Met receptor to restrain the motile response in thyroid cancer cells.

Poorly differentiated thyroid carcinomas are refractory to common anticancer therapies, and novel inhibitors are being tested in these deadly malignancies. The epidermal growth factor receptor (EGFR) tyrosine kinase represents an attractive target for treatment because it is up-regulated in thyroid cancer and plays a role in cancer progression. However, EGFR inhibitors have provided poor results in thyroid carcinomas.We evaluated the possible mechanism underlying the resistance of thyroid cancer cells to EGFR inhibitors.We tested the effect of the EGFR tyrosine kinase inhibitor gefitinib in a panel of thyroid cancer cell lines.We found that in most of the cell lines, although gefitinib inhibited EGFR phosphorylation, it was poorly effective in reducing cell viability. gefitinib, however, was able to inhibit epidermal growth factor-induced cell migration and matrix invasion. In most thyroid cancer cell lines, gefitinib significantly inhibited Akt phosphorylation by inhibiting EGFR activation, but it had limited or no effect on ERK phosphorylation. The poor cell response to gefitinib was associated with genetic alterations, leading to constitutive activation of the ERK pathway, including BRAF(V600E) and HRAS(G12A/Q61R) mutations and RET/PTC1 rearrangement. When BRAF(V600E)-positive thyroid cancer cells were incubated with the specific BRAF inhibitor PLX4032, sensitivity to gefitinib was restored. Similar results were obtained with rat sarcoma and RET/papillary thyroid cancer inhibitors.These results indicate that thyroid cancer resistance to gefitinib is due to the constitutive activation of the mitogenic pathway by either signals downstream of EGFR or other tyrosine kinase receptors. This resistance can be overcome by the combined use of selective inhibitors.

Discoidin Domain Receptor 1 (DDR1) is a collagen receptor tyrosine-kinase that is implicated in tumor progression by contributing to epithelial mesenchymal transition (EMT) and by enhancing tumor cell migration and invasion. We previously demonstrated that, in breast cancer cells, DDR1 functionally cross-talks with IGF-I receptor (IGF-IR), by affecting IGF-IR expression and trafficking. In these cells, DDR1 was able to enhance the stimulatory effects of IGF-I on mitogenesis and invasion suggesting that the DDR1-IGF-IR cross-talk may play a role in cancer progression. Herein, we evaluated whether IGF-I may in turn affect DDR1 expression. Indeed, we demonstrated that in breast cancer cells (MCF-7 and MDA-MB-231), IGF-I was able to upregulate DDR1 protein expression in a time and dose dependent manner. In contrast, DDR1 mRNA levels showed non-significant changes after stimulation with IGF-I. Moreover, we found that DDR1 protein upregulation requires the activation of the PI3K/Akt pathway, while the Erk1/2, the p70/mTOR and the PKC pathways are not involved. Indeed, IGF-I induced DDR1 protein upregulation through a post-trascriptional mechanism involving miR-199a-5p suppression via Akt. We also found that autocrine IGF-II, induced by stable IGF-II cDNA transfection, is also able to elicit significant DDR1 upregulation in breast cancer cells. Similar effects were induced by IGF-II secreted by human cancer associated fibroblasts. Finally, we showed that miR-199a-5p transfection in breast cancer cells, decreased DDR1 expression and affected the response to IGF-I in terms of intracellular signaling through the PI3K/Akt and Erk1/2 pathways, and biological effects such as cell proliferation and migration. These results demonstrate that the protumoral effects of IGF-I include downregulation of miR-199a-5p and consequent upregulation of DDR1 protein. Both these molecules may represent important targets for breast cancers with overactivation of the IGF-IR axis. Citation Format: Chiara Palladino, Roberta Matà, Maria Luisa Nicolosi, Anna Rita Lo Presti, Roberta Malaguarnera, Marco Ragusa, Daniela Sciortino, Andrea Morrione, Marcello Maggiolini, Veronica Vella, Antonino Belfiore. In breast cancer cells IGF-I induces upregulation of DDR1 by suppressing miR-199a-5p via the PI3K/Akt pathway. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4612.

ΔNp73 is a N-terminally truncated p53 family member with a dominant negative function, which is upregulated in cancer. PTEN is a lipid phosphatase, which is involved in the attenuation of tyrosine kinase signaling. PTEN expression is increased by p53, and its function is blunted in several malignancies. Because in most of the thyroid carcinomas, ΔNp73α is upregulated, whereas PTEN expression down regulated, we investigated whether ΔNp73α may influence PTEN expression in this cell model. We found that ΔNp73α overexpression in thyroid cancer cells reduces PTEN expression, whereas ΔNp73α down-regulation by siRNA increases PTEN expression. Real-time PCR indicated that overexpression of ΔNp73α is able to reduce PTEN mRNA levels. Moreover, chromatin immunoprecipitation (ChIP) and luciferase assays indicated that ΔNp73α binds to −1031-779 region of the PTEN promoter, which is a different site than that for p53, thereby inhibiting promoter activity. Interestingly, also the transcriptionally active p73 isoforms (TAp73α and TAp73β) bound to this DNA sequence and, at variance with ΔNp73α, stimulated PTEN promoter activity to an extent similar to that of p53. In accordance with its effect on PTEN protein levels, ΔNp73α increased phospho-Akt protein content and, as a consequence, Mdm2-mediated p53 degradation. This effect of ΔNp73α resulted in increased thyroid cancer cell proliferation and reduced apoptosis and was reverted by the PI3-kinase inhibitor LY294002, indicating the role of Akt pathway in this effect. Taken together, these results indicate a novel p73 regulated mechanism for PTEN expression in thyroid cancer cells, and that, also through this mechanism, ΔNp73α exerts its protumorigenic effect. © 2008 Wiley-Liss, Inc.

p53 family proteins include p53 tumor suppressor, p63, and p73. Despite the high similarity in structure and function with p53, p63, and p73 function in tumor suppression is still controversial. Here, we show that TAp73α, a transcriptionally active p73 isoform, is able to synergize p53 tumor suppressor function in thyroid cancer cells. Indeed, depletion of p73 by small interfering RNA in thyroid cancer cells resulted in a reduced transcriptional activity of p53. Ectopic coexpression of both p53 and TAp73α in thyroid cancer cells resulted in increased transcription and tumor suppressor function compared with p53 or TAp73α alone, as well as in increased p53 protein levels. The enhancing effect of TAp73α on p53 activity is Mdm2 dependent because it is prevented by Mdm2 depletion by small interfering RNA. At least two mechanisms may explain the interference of TAp73α with p53 function. First, in thyroid cancer cells, TAp73α inhibits the effect of p53 on Mdm2 induction by antagonizing p53 at the Mdm2 promoter level. Second, a TAp73α mutant (G264W), which is devoid of DNA binding capability, is still able to increase p53 protein levels by competing with p53 for Mdm2 protein binding. Taken together, these results indicate that in thyroid cancer cells, TAp73α is able to increase p53 protein level and function by interfering with Mdm2-mediated p53 degradation. These results may be useful for designing gene therapies aimed at restoring a normal p53 function in thyroid cancer cells. (Mol Cancer Res 2008;6(1):64–77)

The p73alpha protein is a functional homolog of the p53 tumor suppressor. Although the TP53 gene is frequently mutated in human cancers, the TP73 gene is rarely inactivated. We have found that p73alpha is highly expressed in a significant fraction of anaplastic thyroid cancer, whereas it is not detectable in normal thyroid epithelial cells or in papillary and follicular thyroid cancer cells. Interestingly, the tumor suppression function of p73alpha is actively restrained in anaplastic thyroid cancer cells. We have also found that c-Abl tyrosine kinase, an activator of p73, is excluded from the nucleus of p73alpha-positive thyroid cancer cells; whereas c-Abl undergoes nuclear-cytoplasmic shuttling in normal thyroid and p73-negative thyroid cancer cells. We constructed an AblNuk-FK506-binding protein (FKBP) fusion protein to enforce the nuclear accumulation of an inducible Abl kinase. Activation of this nuclear AblNuk-FKBP by dimerization with AP20187 in anaplastic thyroid cancer cells increased the levels of p73alpha and p21Cip1 and caused p73-dependent apoptosis. These results suggest subcellular segregation of c-Abl from p73 to be a strategy for disrupting the tumor suppression function of p73alpha.