Aniello Cerrato

Beta- and gamma-catenin expression in thyroid carcinomas

Cadherins are calcium‐dependent cell–cell adhesion molecules whose intracellular domain forms a complex with proteins required for their function, called catenins. Down‐regulation of cadherins has frequently been detected in many types of human carcinomas, being associated with tumour progression. The present study investigates the immunohistochemical expression of E‐cadherin and beta‐ and gamma‐catenin in 27 human thyroid carcinomas. E‐cadherin immunoreactivity was found to be decreased at cell–cell contacts in 8/15 (53 per cent) papillary, 5/7 (71 per cent) follicular, and 5/5 (100 per cent) anaplastic carcinomas. Beta‐catenin membrane localization was found to be decreased in 6/15 (40 per cent) papillary, 2/7 (28 per cent) follicular, and 5/5 (100 per cent) anaplastic carcinomas. Gamma‐catenin expression was partially or totally lost in 13/15 (86 per cent) papillary, 6/7 (85 per cent) follicular, and 5/5 (100 per cent) anaplastic carcinomas. A normal pattern of expression for these three molecules was observed in areas of normal tissue in each sample. These data indicate that in addition to E‐cadherin, catenins are also down‐regulated at cell–cell junctions in thyroid tumours and could represent potentially useful differentiation and/or transformation markers. The high frequency of alterations of gamma‐catenin expression found in thyroid carcinomas suggests an important role for this gene product in thyroid carcinogenesis.

Molecular genetics of medullary thyroid carcinoma: the quest for novel therapeutic targets

Medullary thyroid carcinoma (MTC) is a rare tumour arising from neural crest-derived parafollicular C-cells. Metastatic MTC patients are incurable because the cancer does not respond to radiotherapy or chemotherapy. The REarranged during Transfection (RET) proto-oncogene plays a key role in the development of MTC. However, one-half of the sporadic MTC do not carry RET mutations. Mice models and early evidence obtained in human samples suggest that other genes, including those encoding components of the RB1 (retinoblastoma) and TP53 tumour-suppressor pathways, may be involved in MTC formation. Here, we review the data on the involvement of genes acting in the RET and RB1/TP53 pathways in MTC. Understanding genetic lesions that occur in MTC is a prerequisite to identifying molecular therapeutic targets in MTC and in improving the efficacy of RET-targeted therapies.

H4(D10S170), a gene frequently rearranged with RET in papillary thyroid carcinomas: functional characterization

Human thyroid papillary carcinomas are characterized by rearrangements of the RET protooncogene with a number of heterologous genes, which generate the RET/papillary thyroid carcinoma (PTC) oncogenes. One of the most frequent variants of these recombination events is the fusion of the intracellular kinase-encoding domain of RET to the first 101 amino acids of a gene named H4(D10S170). We have characterized the H4(D10S170) gene product, showing that it is a ubiquitously expressed 55 KDa nuclear and cytosolic protein that is phosphorylated following serum stimulation. This phosphorylation was found to depend on mitogen-activated protein kinase (MAPK) Erk1/2 activity and to be associated to the relocation of H4(D10S170) from the nucleus to the cytosol. Overexpression of the H4(D10S170) gene was able to induce apoptosis of thyroid follicular epithelial cells; conversely a carboxy-terminal truncated H4(D10S170) mutant H4(1–101), corresponding to the portion included in the RET/PTC1 oncoprotein, behaved as dominant negative on the proapoptotic function and nuclear localization of H4(D10S170). Furthermore, conditional expression of the H4(D10S170)-dominant negative truncated mutant protected cells from stress-induced apoptosis. The substitution of serine 244 with alanine abrogated the apoptotic function of H4(D10S170). These data suggest that loss of the H4(D10S170) gene function might have a role in thyroid carcinogenesis by impairing apoptosis.

Use of poly ADP-ribose polymerase [PARP] inhibitors in cancer cells bearing DDR defects: the rationale for their inclusion in the clinic.

BackgroundDNA damage response (DDR) defects imply genomic instability and favor tumor progression but make the cells vulnerable to the pharmacological inhibition of the DNA repairing enzymes. Targeting cellular proteins like PARPs, which cooperate and complement molecular defects of the DDR process, induces a specific lethality in DDR defective cancer cells and represents an anti-cancer strategy. Normal cells can tolerate the DNA damage generated by PARP inhibition because of an efficient homologous recombination mechanism (HR); in contrast, cancer cells with a deficient HR are unable to manage the DSBs and appear especially sensitive to the PARP inhibitors (PARPi) effects.Main bodyIn this review we discuss the proof of concept for the use of PARPi in different cancer types and the success and failure of their inclusion in clinical trials.The PARP inhibitor Olaparib [AZD2281] has been approved by the FDA for use in pretreated ovarian cancer patients with defective BRCA1/2 genes, and by the EMEA for maintenance therapy in platinum sensitive ovarian cancer patients with defective BRCA1/2 genes. BRCA mutations are now recognised as the molecular targets for PARPi sensitivity in several tumors. However, it is noteworthy that the use of PARPi has shown its efficacy also in non-BRCA related tumors. Several trials are ongoing to test different PARPi in different cancer types. Here we review the concept of BRCAness and the functional loss of proteins involved in DDR/HR mechanisms in cancer, including additional molecules that can influence the cancer cells sensitivity to PARPi. Given the complexity of the existing crosstalk between different DNA repair pathways, it is likely that a single biomarker may not be sufficient to predict the benefit of PARP inhibitors therapies. Novel general assays able to predict the DDR/HR proficiency in cancer cells and the PARPi sensitivity represent a challenge for a personalized therapy.ConclusionsPARP inhibition is a potentially important strategy for managing a significant subset of tumors. The discovery of both germline and somatic DNA repair deficiencies in different cancer patients, together with the development of new PARP inhibitors that can kill selectively cancer cells is a potent example of targeting therapy to molecularly defined tumor subtypes.

CCDC6 represses CREB1 activity by recruiting histone deacetylase 1 and protein phosphatase 1.

RET/papillary thyroid carcinoma 1 (PTC1) oncogene is frequently activated in human PTCs. It is characterized by the fusion of the intracellular kinase-encoding domain of RET to the first 101 amino acids of CCDC6. The aim of our work is to characterize the function of the CCDC6 protein to better understand the function of its truncation, that results in the loss of the expression of one allele, in the process of thyroid carcinogenesis. Here, we report that CCDC6 interacts with CREB1 and represses its transcriptional activity by recruiting histone deacetylase 1 and protein phosphatase 1 proteins at the CRE site of the CREB1 target genes. Finally, we show an increased CREB1 phosphorylation and activity in PTCs carrying the RET/PTC1 oncogene. Consistently, an increased expression of two known CREB1 target genes, AREG and cyclin A, was observed in this subgroup of thyroid papillary carcinomas. Therefore, the repression of CREB1 activity by CCDC6 has a critical function in the development of human thyroid papillary carcinomas carrying RET/PTC1 activation.

New therapeutic perspectives in CCDC6 deficient lung cancer cells

Non‐small cell lung cancer (NSCLC) is the main cause of cancer‐related death worldwide and new therapeutic strategies are urgently needed. In this study, we have characterized a panel of NSC lung cancer cell lines for the expression of coiled‐coil‐domain containing 6 (CCDC6), a tumor suppressor gene involved in apoptosis and DNA damage response. We show that low CCDC6 protein levels are associated with a weak response to DNA damage and a low number of Rad51 positive foci. Moreover, CCDC6 deficient lung cancer cells show defects in DNA repair via homologous recombination. In accordance with its role in the DNA damage response, CCDC6 attenuation confers resistance to cisplatinum, the current treatment of choice for NSCLC, but sensitizes the cells to olaparib, a small molecule inhibitor of the repair enzymes PARP1/2. Remarkably, the combination of the two drugs is more effective than each agent individually, as demonstrated by a combination index <1. Finally, CCDC6 is expressed at low levels in about 30% of the NSCL tumors we analyzed by TMA immunostaining. The weak CCDC6 protein staining is significatively correlated with the presence of lymph node metastasis (p ≤ 0.02) and negatively correlated to the disease free survival (p ≤ 0.01) and the overall survival (p ≤ 0.05). Collectively, the data indicate that CCDC6 levels provide valuable insight for OS. CCDC6 could represent a predictive biomarker of resistance to conventional single mode therapy and yield insight on tumor sensitivity to PARP inhibitors in NSCLC.

USP7 inhibitors, downregulating CCDC6, sensitize lung neuroendocrine cancer cells to PARP-inhibitor drugs

OBJECTIVES CCDC6 gene product is a tumor-suppressor pro-apoptotic protein, substrate of ATM, involved in DNA damage response and repair. Altered levels of CCDC6 expression are dependent on post-translational modifications, being the de-ubiquitinating enzyme USP7 responsible of the fine tuning of the CCDC6 stability. Thus, our aim was to investigate CCDC6 and USP7 expression levels in Lung-Neuroendocrine Tumors (L-NETs) to verify if they correlate and may be exploited as novel predictive therapeutic markers. MATERIALS AND METHODS Tumor tissues from 29 L-NET patients were investigated on tissue microarrays. CCDC6 levels were scored and correlated with immunoreactivity for USP7. Next generation sequencing (NGS) of a homogenous group of Large Cell Neuroendocrine Carcinoma (LCNEC) (N=8) was performed by Ion AmpliSeq NGS platform and the Ion AmpliSeq Cancer Hotspot Panel v2. The inhibition of USP7, using P5091, was assayed in vitro to accelerate CCDC6 turnover in order to sensitize the neuroendocrine cancer cells to PARP-inhibitors, alone or in association with cisplatinum. RESULTS The immunostaining of 29 primary L-NETs showed that the intensity of CCDC6 staining correlated with the levels of USP7 expression (p≤0.05). The NGS analysis of 8 LCNEC revealed mutations in the hot spot regions of the p53 gene (in 6 out of 8). Moreover, gene polymorphisms were identified in the druggable STK11, MET and ALK genes. High intensity of p53 immunostaining was reported in the 6 tissues carrying the TP53 mutations. The inhibition of USP7 by P5091 accelerated the degradation of CCDC6 versus control in cycloheximide treated L-NET cells in vitro and sensitized the cells to PARP-inhibitors alone and in combination with cisplatinum. CONCLUSION Our data suggest that CCDC6 and USP7 have a predictive value for the clinical usage of USP7 inhibitors in combination with the PARP-inhibitors in L-NET in addition to standard therapy.

Analysis of cadherin/catenin complexes in transformed thyroid epithelial cells: Modulation by beta 1 integrin subunit

We have analysed the expression of cadherin/catenin complex molecules in PC C13 rat thyroid cells transformed in vitro with different oncogenes. No significant downregulation of either E-cadherin, alpha-, beta- and gamma-catenin was detected following the introduction of activated forms of myc, adenovirus E1A, ras, raf, myc + ras, E1A + raf. However, ras- and raf-transformed PC C13 cells showed altered adherens junctions. An altered distribution of cadherin/catenin complexes characterized by radially oriented membrane spikes perpendicular to cell edges was the most prominent feature evidenced by immunofluorescence. No beta1 integrin localization was observed in areas where this altered pattern of E-cadherin expression was detected. However, beta1 integrin subunit expression was detected at areas of cell-cell contact where E-cadherin showed a normal pattern of expression. Furthermore, ras- and raf-transformed PC C13 cells showed the ability to migrate in collagen gels, in contrast to their normal untransformed counterpart. Overexpression of beta1 integrin was found to restore normal E-cadherin localization at cell-cell contacts and to partially inhibit the ability to migrate in collagen gels. Finally, two cell lines obtained by ras transformation in vivo, and derived from a rat primary thyroid carcinoma (TK6) and its lung metastasis (MPTK6), were found to have lost gamma-catenin expression. TK6 lost also E-cadherin expression and membrane localization of alpha-catenin. These results suggest that: i) in vitro thyroid cell transformation is associated to a change in cadherin/catenin complexes distribution rather than to a decrease in expression; ii) in vivo transformation is associated to the loss of expression of some of these molecules likely due to tumor progression; iii) alterations in beta1 integrin subunit expression can result in changes in cadherin/catenin function thus implying that an integrin-cadherin synergy may exist in thyroid cells.

The combined effect of USP7 inhibitors and PARP inhibitors in hormone-sensitive and castration-resistant prostate cancer cells

Purpose of the study Reduced levels of the tumor suppressor protein CCDC6 sensitize cancer cells to the treatment with PARP-inhibitors. The turnover of CCDC6 protein is regulated by the de-ubiquitinase USP7, which also controls the androgen receptor (AR) stability. Here, we correlated the expression levels of CCDC6 and USP7 proteins in primary prostate cancers (PC). Moreover, we tested the efficacy of the USP7 inhibitors, in combination with PARP-inhibitors as a novel therapeutic option in advanced prostate cancer. Experimental techniques PC cells were exposed to USP7 inhibitor, P5091, together with cycloheximide, to investigate the turnover of the USP7 substrates, AR and CCDC6. As outcome of the AR downregulation, transcription targets of AR and its variant V7 were examined by qPCR. As a result of CCDC6 degradation, the induction of PARP inhibitors sensitivity was evaluated by analyzing PC cells viability and foci formation. We scored and correlated CCDC6 and USP7 expression levels in a prostate cancer tissue microarray (TMA). Results P5091 accelerated the degradation of AR and V7 isoform affecting PSA, UBE2C, CDC20 transcription and PC cells proliferation. Moreover, P5091 accelerated the degradation of CCDC6 sensitizing the cells to PARP-inhibitors, that acted sinergistically with genotoxic agents. The immunohistochemical analysis of both CCDC6 and USP7 proteins exhibited significant correlation for the intensity of staining (p ≤ 0.05). Data interpretation Thus, CCDC6 and USP7 represent predictive markers for the combined treatment of the USP7-inhibitors and PARP-inhibitors in advanced prostate cancer.

The PTC oncogene is able to dedifferentiate a rat thyroid epithelial cell line in culture

We have recently cloned a new oncogene from human papillary thyroid carcinomas, which we have designatedPTC. This oncogene consists of a chimeric gene, the 5′-end of which corresponds to a gene of unknown function, designated H4, while the 3′ portion corresponds to the tyrosine kinase domain of theRET proto-oncogene. We constructed a retroviral vector containing thePTC oncogene under the transcriptional control of the Moloney LTR, and then produced the corresponding defective retrovirus by transfecting the retroviral vector onto Psi-2 cells. We subsequently used this retrovirus to infect a differentiated rat thyroid cell line (PC-C1-3) which is dependent on TSH for growth. Upon infection with thePTC virus the PC-C1-3 cells no longer depended on TSH for growth. Furthermore, the infected cells lost completely their differentiated functions,i.e. thyroglobulin and TSH-receptor genes expression and iodide uptake. However, they retained their non malignant phenotype in that they were not able to grow in semisolid media nor in the athymic mice. The introduction in the PC-C1-3 cell line of both thePTC and the activated viral Ha-ras oncogenes resulted in the appearance of a completely undifferentiated and malignant phenotype. These results demonstrate that:a) ThePTC oncogene, which plays an important role in human thyroid carcinogenesis, is also able to induce the complete dedifferentiation of rat thyroid cellsin vitro;b) Two cytoplasmic oncogenes (Ha-ras andPTC) cooperate in the induction of a fully malignant phenotype of a thyroid differentiated cell line.RiassuntoIl nostro laboratorio ha recentemente clonato un nuovo oncogene da carcinomi tiroidei papillari umani: tale oncogene è stato denominatoPTC. Tale sequenza trasformante è una chimera costituita dal dominio tirosino-chinasi del proto-oncogeneRET e da una porzione amino-terminale di un gene in via di caratterizzazione che abbiamo denominato H4. Abbiamo costruito un vettore retrovirale contenente l’oncogenePTC sotto il controllo trascrizionale della «Long Terminal Repeat» del virus della Leucemia di Moloney (MoLTR) e abbiamo successivamente generato il corrispettivo retrovirus difettivo trasfettando tale vettore nelle cellule competenti per il packaging (Psi-2). Il retrovirus così ottenuto è stato utilizzato per infettare una linea cellulare epiteliale differenziata di tiroide di ratto, le PC-C1-3, la quale necessita di ormone tireotropo (TSH) per la crescita. In seguito all’infezione tali cellule sono diventate indipendenti dal TSH e hanno perso completamente i loro «markers» di differenziazione, quali sintesi e secrezione di tireoglobulina, espressione del recettore per il TSH e captazione degli ioduri. Le cellule tuttavia hanno mantenuto il loro fenotipo non maligno in quanto non si sono dimostrate capaci di crescere in terreno semisolido ne di indurre tumori se inoculate nel topo atimico. Invece l’introduzione contemporanea diPTC e dell’oncogene virale Ha-ras nelle cellule PC-C1-3 ha indotto un fenotipo completamente trasformato e indifferenziato. Questi risultati dimostrano che:a) l’oncogenePTC, che svolge un ruolo importante nella cancerogenesi tiroidea umana, è anche in grado di indurre una completa dedifferenziazione in cellule tiroideein vitro;b) due oncogeni citoplasmatici (Ha-ras ePTC) sono in grado di cooperare nella induzione di un fenotipo completamente maligno in questa linea tiroidea differenziata.