Structural deciphering of the NG2/CSPG4 proteoglycan multifunctionality.

The chondroitin sulfate proteoglycan 4 ( CSPG4) gene encodes a transmembrane proteoglycan (PG) constituting the largest and most structurally complex macromolecule of the human surfaceome. Its transcript shows an extensive evolutionary conservation and, due to the elaborated intracellular processing of the translated protein, it generates an array of glycoforms with the potential to exert variant-specific functions. CSPG4-mediated molecular events are articulated through the interaction with more than 40 putative ligands and the concurrent involvement of the ectodomain and cytoplasmic tail. Alternating inside-out and outside-in signal transductions may thereby be elicited through a tight functional connection of the PG with the cytoskeleton and its regulators. The potential of CSPG4 to influence both types of signaling mechanisms is also asserted by its lateral mobility along the plasma membrane and its intersection with microdomain-restricted internalization and endocytic trafficking. Owing to the multitude of molecular interplays that CSPG4 may engage, and thanks to a differential phosphorylation of its intracellular domain accounted by crosstalking signaling pathways, the PG stands out for its unique capability to affect numerous cellular phenomena, including those purporting pathologic conditions. We discuss here the progresses made in advancing our understanding about the structural-functional bases for the ability of CSPG4 to widely impact on cell behavior, such as to highlight how its multivalency may be exploited to interfere with disease progression.-Tamburini, E., Dallatomasina, A., Quartararo, J., Cortelazzi, B., Mangieri, D., Lazzaretti, M., Perris, R. Structural deciphering of the NG2/CSPG4 proteoglycan multifunctionality.

The telomere-binding protein Tbf1 demarcates snoRNA gene promoters in Saccharomyces cerevisiae.

Small nucleolar RNAs (snoRNAs) play a key role in ribosomal RNA biogenesis, yet factors controlling their expression are unknown. We found that the majority of Saccharomyces snoRNA promoters display an aRCCCTaa sequence motif at the upstream border of a TATA-containing nucleosome-free region. Genome-wide ChIP-seq analysis showed that these motifs are bound by Tbf1, a telomere-binding protein known to recognize mammalian-like T(2)AG(3) repeats at subtelomeric regions. Tbf1 has over 100 additional promoter targets, including several other genes involved in ribosome biogenesis and the TBF1 gene itself. Tbf1 is required for full snoRNA expression, yet it does not influence nucleosome positioning at snoRNA promoters. In contrast, Tbf1 contributes to nucleosome exclusion at non-snoRNA promoters, where it selectively colocalizes with the Tbf1-interacting zinc-finger proteins Vid22 and Ygr071c. Our data show that, besides the ribosomal protein gene regulator Rap1, a second telomere-binding protein also functions as a transcriptional regulator linked to yeast ribosome biogenesis.

Receptor tyrosine kinase profiles and human papillomavirus status in oropharyngeal squamous cell carcinoma.

BACKGROUND: Human papillomavirus (HPV)-positive and HPV-negative oropharyngeal squamous cell carcinomas (OSCCs) are two distinct entities. We defined the molecular profiles of druggable receptor tyrosine kinases (RTKs) in both groups. MATERIALS AND METHODS: E5 expression and RTK alterations were studied in 17 HPV-positive and 59 HPV-negative formalin-fixed OSCCs. RTK activation was explored in further 12 frozen OSCCs. RESULTS: The HPV-positive OSCCs showed E5 expression and 33.3% expressed low level of HER2. The HPV-negative OSCCs showed HER2 expression (31.2%), increased HER2 gene copy number (46.51%, P = 0.045) and HER2 activation through HER2/EGFR heterodimerisation; HER3 (51.06%, P = 0.008) and neuregulin (65.63%; P = 0.03) expression, HER3 activation and HER3/EGFR heterodimerisation; and increased IGF-1R copy number (40.50%, P = 0.021), high IGF-1R cDNA values (P = 0.002), IGF-1R activation and expression of IGF1/2 and amphiregulin. PI3KCA mutations/expression/increased gene copy number and PTEN mutations were found in both groups, whereas PTEN gene loss was only observed in the HPV-positive cases. CONCLUSION: Human papillomavirus-positive and HPV-negative OSCC showed different RTK profiles. In HPV-positive cases, it would be interesting to study the expression of E5, which may modulate EGFR turnover and activate VEGF and PDGFRß. In HPV-negative cases, HER3 may be a promising druggable biomarker that deserves further investigation. PI3KCA and PTEN alterations encourage the promising clinical evaluation of PI3K/mTOR inhibitor activity in OSCC, particularly in HPV-positive/PI3KCA-mutated OSCCs because they may be driven by PI3KCA mutation alone.

Functional Genomics Uncover the Biology behind the Responsiveness of Head and Neck Squamous Cell Cancer Patients to Cetuximab.

PURPOSE: To identify the tumor portrait of the minority of head and neck squamous cell carcinoma (HNSCC) patients with recurrent-metastatic (RM) disease who upon treatment with platinum-based chemotherapy plus cetuximab present a long-lasting response. EXPERIMENTAL DESIGN: The gene expression of pretreatment samples from 40 HNSCC-RM patients, divided in two groups [14 long-progression-free survival (PFS) and 26 short-PFS (median = 19 and 3 months, respectively)], was associated with PFS and was challenged against a dataset from metastatic colon cancer patients treated with cetuximab. For biologic analysis, we performed functional and subtype association using gene set enrichment analysis, associated biology across all currently available HNSCC signatures, and inferred drug sensitivity using data from the Cancer Genomic Project. RESULTS: The identified genomic profile exhibited a significant predictive value that was essentially confirmed in the single publicly available dataset of cetuximab-treated patients. The main divergence between long- and short-PFS groups was based on developmental/differentiation status. The long-PFS patients are characterized by basal subtype traits such as strong EGFR signaling phenotype and hypoxic differentiation, further validated by the significantly higher association with the hypoxia metagene. The short-PFS patients presented a strong activation of RAS signaling confirmed in an in vitro model of two isogenic HNSCC cell lines sensitive or resistant to cetuximab. The predicted drug sensitivity for all four EGFR inhibitors was higher in long- versus short-PFS patients (P range: <0.0022-1e-07). CONCLUSIONS: Our data uncover the biology behind response to platinum-based chemotherapy plus cetuximab in RM-HNSCC cancer and may have translational implications improving treatment selection. Clin Cancer Res; 22(15); 3961-70. ©2016 AACRSee related commentary by Chau and Hammerman, p. 3710.

Clinical activity of androgen deprivation therapy in patients with metastatic/relapsed androgen receptor-positive salivary gland cancers.

BACKGROUND: Androgen deprivation therapy has some clinical activity in selected salivary gland cancer histotypes, with androgen receptor expression. METHODS: We retrospectively analyzed patients with androgen receptor-expressing recurrent/metastatic salivary gland cancer, treated with androgen deprivation therapy. Protein expression of androgen receptor and ErbB family members was investigated. Progression-free survival (PFS) and overall survival (OS) were the main endpoints. RESULTS: Seventeen patients were identified. No significant toxicities were reported. Overall response rate was 64.7%; 3-year PFS and 5-year OS were 11.8% and 19.3%, respectively. Androgen receptor overexpression may be sustained by gain of chromosome X (58%) and TP53 mutation (44%). No association between response to androgen deprivation therapy and epidermal growth factor receptor (EGFR), human epidermal growth factor receptor (HER)2, HER3 expression, PIK3CA mutations, or phosphatase and tensin homolog (PTEN) deletion was identified. CONCLUSION: We confirm the activity of androgen deprivation therapy in androgen receptor-expressing recurrent/metastatic salivary gland cancers. The hypothesis that an androgen receptor increased gene copy number may represent a possible mechanism of primary resistance should be further investigated.

Epithelioid peritoneal mesothelioma: a hybrid phenotype within a mesenchymal-epithelial/epithelial-mesenchymal transition framework.

The aim of this study was to reconsider the biological characteristics of epithelioid malignant peritoneal mesothelioma (E-MpM) in the light of new concepts about epithelial mesenchymal transition and mesenchymal epithelial reverse transition (EMT/MErT) and the role of epigenetic reprogramming in this context. To this end we profiled surgical specimens and derived cells cultures by a number of complementary approaches i.e. immunohistochemistry, immunofluorescence, in situ hybridization, biochemistry, pluripotent stem cell arrays, treatments with cytokines, growth factors and specific inhibitors.The analyses of the surgical specimens showed that i) EZH2 is expressed throughout the spectrum of MpM, ii) that E-MpM (including the high-grade undifferentiated form) are characterised by c-MYC and miRNA 17-5p expression, and iii) that progression to sarcomatoid MpM is dictated by EMT regulators. They also showed that E-MpM expressed c-MET and are enriched in E- and P-cadherins- and VEGFR2-expressing CSCs, thus strongly supporting a role for MErT reprogramming in endowing E-MpM tumour cells with stemness and plasticity, and hence with a drug resistant phenotype. The cell culture-based experiments confirmed the stemness traits and plasticity of E-MpM, and support the view that EZH2 is a druggable target in this tumor.

Smoothened (SMO) receptor mutations dictate resistance to vismodegib in basal cell carcinoma.

Basal cell carcinomas (BCCs) and a subset of medulloblastomas are characterized by loss-of-function mutations in the tumor suppressor gene, PTCH1. PTCH1 normally functions by repressing the activity of the Smoothened (SMO) receptor. Inactivating PTCH1 mutations result in constitutive Hedgehog pathway activity through uncontrolled SMO signaling. Targeting this pathway with vismodegib, a novel SMO inhibitor, results in impressive tumor regression in patients harboring genetic defects in this pathway. However, a secondary mutation in SMO has been reported in medulloblastoma patients following relapse on vismodegib to date. This mutation preserves pathway activity, but appears to confer resistance by interfering with drug binding. Here we report for the first time on the molecular mechanisms of resistance to vismodegib in two BCC cases. The first case, showing progression after 2 months of continuous vismodegib (primary resistance), exhibited the new SMO G497W mutation. The second case, showing a complete clinical response after 5 months of treatment and a subsequent progression after 11 months on vismodegib (secondary resistance), exhibited a PTCH1 nonsense mutation in both the pre- and the post-treatment specimens, and the SMO D473Y mutation in the post-treatment specimens only. In silico analysis demonstrated that SMO(G497W) undergoes a conformational rearrangement resulting in a partial obstruction of the protein drug entry site, whereas the SMO D473Y mutation induces a direct effect on the binding site geometry leading to a total disruption of a stabilizing hydrogen bond network. Thus, the G497W and D473Y SMO mutations may represent two different mechanisms leading to primary and secondary resistance to vismodegib, respectively.

Activity of abiraterone in rechallenging two AR-expressing salivary gland adenocarcinomas, resistant to androgen-deprivation therapy.

Androgen-deprivation therapy (ADT) has been reported to be active in androgen receptor (AR)-expressing, relapsed/metastatic (RM), salivary gland cancers (SGCs). Abiraterone, an inhibitor of androgen synthesis, has recently been approved as a second-line treatment in hormone-resistant (HR) prostate cancer (PCa) patients. Two patients with AR-positive HR-RM adenocarcinoma, NOS of the salivary glands have been treated with abiraterone. This is the first time that this agent has been reported to be active in tumors other than HRPCa. Immunohistochemical analysis showed overexpression of EGFR, HER2, and HER3 in both untreated primary tumors. Sequencing analysis revealed a TP53 non-functional mutation in one case and a PIK3CA-activating mutation in the other. In conclusion, second line activity of ADT in AR-expressing, adenocarcinoma, NOS of salivary glands further strengthens the pathogenic and therapeutic role of AR signaling in AR-positive SGCs.

Tp53 status as guide for the management of ethmoid sinus intestinal-type adenocarcinoma.

OBJECTIVE: Intestinal-type adenocarcinoma (ITAC) of the ethmoid sinus is a rare, occupational-related tumor. Optimal treatment consists of surgery and radiotherapy, while chemotherapy is still investigational. The molecular profile of ITAC is characterized by the occurrence of TP53 mutations associated with genotoxic agents such as wood dust. We investigated the role of p53 functionality in relation to the primary treatment. MATERIALS AND METHODS: We retrospectively reviewed 100 medical charts of consecutive patients with a first diagnosis of ITAC treated at our Institute; 74 patients were evaluable for TP53 analysis. Thirty (41%) were treated from 1991 to 2006 with craniofacial resection followed by radiotherapy (Group A), compared with 44 patients (59%) treated from 1996 to 2006 with cisplatin-based induction chemotherapy (PFL) followed by standard treatment (Group B). RESULTS: Five-year OS in Group A was 42%, while in Group B it was 70% (p = 0.041); 5-year DFS in Group A was 40%, while in Group B it was 66%, (p = 0.009) (p = 0.061 and 0.003 at Cox multivariable OS and DFS analyses). Analyzing each group according to p53 functional status, only for Group B patients (who received preoperative chemotherapy) both OS and DFS were in favor of functional p53 (p = 0.023 and p = 0.010, respectively). No impact of p53 functional status as a biomarker was observed in Group A. CONCLUSIONS: Functional p53 may predict PFL-chemotherapy efficacy, offering a possible increase in survival when induction chemotherapy is given to a selected population. On the other hand, upcoming innovative approaches should be explored in the presence of non-functional p53.

TP53 mutations and pathologic complete response to neoadjuvant cisplatin and fluorouracil chemotherapy in resected oral cavity squamous cell carcinoma.

PURPOSE To find out if TP53 functional status predicts response to neoadjuvant chemotherapy and thus may be helpful during treatment decision making of oral cavity squamous cell carcinoma (SCC) patients. PATIENTS AND METHODS We analyzed the predictive value of TP53 mutations and their functional status on the basis of the transactivation activity of p53 mutant proteins in 53 pretreatment biopsies of oral cavity SCC patients receiving primary cisplatin and fluorouracil chemotherapy followed by surgery. Results The surgical specimens showed that 15 patients (28%) achieved a pathologic complete remission (pCR) at both T and N sites, and 38 patients had residual tumor cells. Among the 53 pretreatment biopsies, 24 (45%) displayed TP53 mutations: 22 single-nucleotide substitutions and two deletions. According to functional status that could be determined only for the 22 substitutions, 21 mutations were nonfunctional and one was partially functional. TP53 mutation was found in four (27%) of 15 patients who achieved a pCR and in 20 (53%) of 38 nonresponder patients; the difference was not statistically significant (P = .12). In contrast, two (14%) of 14 cases with pCR carried a nonfunctional TP53 mutation, a frequency significantly less than that found in the nonresponders (19 [51%] of 37; P = .02). TP53 mutation predicted pCR in four (17%) of 24 patients and a nonfunctional mutation in only two (9%) of 22 patients. CONCLUSION The results indicate that the loss of function (transactivation activities) of p53 mutant proteins may predict a significant low pCR rate and suboptimal response to cisplatin-based neoadjuvant chemotherapy in patients with oral cavity SCC.

Treatment relevant target immunophenotyping of 139 salivary gland carcinomas (SGCs).

Salivary gland carcinomas (SGCs) are rare tumors encompassing a wide spectrum of histologic/biologic entities. Standard non-surgical treatments are ineffective in case of advanced disease. Our aim was to analyze SGCs deregulation gene profiles that could become target for innovative treatment options. Samples from 139 patients with primary, recurrent and/or metastatic SGCs were investigated by immunohistochemistry for protein encoded by tyrosine kinases receptors (TKRs) i.e. c-kit, HER2, EGFR and hormonal receptors, i.e. androgen (AR), estrogen (ER) and progesterone receptors (PgR). In 26 cases, the HER2 immunohistochemical analysis was complemented by fluorescence in-situ hybridization analysis. EGFR was the most expressed TKRs (71%) and it was found across all histotypes. c-Kit expression was mainly restricted to adenoid cystic carcinoma (78%) while HER2 expression, mostly sustained by gene amplification, correlated with salivary duct carcinoma (SDC) in 44% of cases and adenocarcinoma, not otherwise specified (AD, NOS) in 21% of cases. With respect to histogenetic classification, TKRs expression occurred more often in tumors derived from intercalated duct rather than excretory ones with the only exception of HER2. AR was found in 13% of samples, restricted to SDC and AD, NOS and it was co-expressed with HER2 in more than half of the SDC cases. ER and PgR positivity was never detected. This TK-hormonal receptors analysis identify a histotype-specific profiles that could be exploited for better selecting patients for innovative treatment within prospective studies.