SOX2 Epidermal Overexpression Promotes Cutaneous Wound Healing via Activation of EGFR/MEK/ERK Signaling Mediated by EGFR Ligands

Oral mucosa contains a unique transcriptional network that primes oral wounds for rapid resolution in humans. Our previous work identified genes that were consistently upregulated in the oral mucosa and demonstrated that induction of one of the identified genes, transcription factor SOX2, promoted cutaneous wound healing in mice. In this study, we investigated the molecular and cellular mechanisms by which SOX2 accelerates wound healing in skin. RNA-sequencing analysis showed that SOX2 induced a proliferative and wound-activated phenotype in skin keratinocytes prior to wounding. During wound healing, SOX2 induced proliferation of epithelial and connective tissue cells and promoted angiogenesis. Chromatin immunoprecipitation assay revealed that SOX2 directly regulates expression of EGFR ligands, resulting in activation of EGFR. In vitro, skin keratinocytes overexpressing SOX2 promoted cell migration via the EGFR/MEK/ERK pathway. We conclude that induction of SOX2 in skin keratinocytes accelerates cutaneous wound healing by promoting keratinocyte migration and proliferation, and enhancement of angiogenesis via upregulation of EGFR ligands and activation of EGFR/MEK/ERK pathway. Through the identification of putative cutaneous SOX2 targets, such as HBEGF, this study opens venues to determine clinical targets for treatment of skin wounds.

Effects of palbociclib on oral squamous cell carcinoma and the role of PIK3CA in conferring resistance

Objective

Lack of effective therapies remains a problem in the treatment of oral squamous cell carcinoma (OSCC), especially in patients with advanced tumors. OSCC development is driven by multiple aberrancies within the cell cycle pathway, including amplification of cyclin D1 and loss of p16. Hence, cell cycle inhibitors of the CDK4/6-cyclin D axis are appealing targets for OSCC treatment. Here, we determined the potency of palbociclib and identified genetic features that are associated with the response of palbociclib in OSCC.

Methods

The effect of palbociclib was evaluated in a panel of well-characterized OSCC cell lines by cell proliferation assays and further confirmed by in vivo evaluation in xenograft models. PIK3CA-mutant isogenic cell lines were used to investigate the effect of PIK3CA mutation towards palbociclib response.

Results

We demonstrated that 80% of OSCC cell lines are sensitive to palbociclib at sub-micromolar concentrations. Consistently, palbociclib was effective in controlling tumor growth in mice. We identified that palbociclib-resistant cells harbored mutations in PIK3CA. Using isogenic cell lines, we showed that PIK3CA mutant cells are less responsive to palbociclib as compared to wild-type cells with concurrent upregulation of CDK2 and cyclin E1 protein levels. We further demonstrated that the combination of a PI3K/mTOR inhibitor (PF-04691502) and palbociclib completely controlled tumor growth in mice.

Conclusions

This study demonstrated the potency of palbociclib in OSCC models and provides a rationale for the inclusion of PIK3CA testing in the clinical evaluation of CDK4/6 inhibitors and suggests combination approaches for further clinical studies.

Gβγ signaling to the chemotactic effector P-REX1 and mammalian cell migration is directly regulated by Gαq and Gα13 proteins

G protein-coupled receptors stimulate Rho guanine nucleotide exchange factors that promote mammalian cell migration. Rac and Rho GTPases exert opposing effects on cell morphology and are stimulated downstream of Gβγ and Gα_12/13 or Gα_q, respectively. These Gα subunits might in turn favor Rho pathways by preventing Gβγ signaling to Rac. Here, we investigated whether Gβγ signaling to phosphatidylinositol 3,4,5-trisphosphate-dependent Rac exchange factor 1 (P-REX1), a key Gβγ chemotactic effector, is directly controlled by Rho-activating Gα subunits. We show that pharmacological inhibition of Gα_q makes P-REX1 activation by G_q/G_i-coupled lysophosphatidic acid receptors more effective. Moreover, chemogenetic control of G_i and G_q by designer receptors exclusively activated by designer drugs (DREADDs) confirmed that G_i differentially activates P-REX1. GTPase-deficient Gα_qQL and Gα₁₃QL variants formed stable complexes with Gβγ, impairing its interaction with P-REX1. The N-terminal regions of these variants were essential for stable interaction with Gβγ. Pulldown assays revealed that chimeric Gα_13-i2QL interacts with Gβγ unlike to Gα_i2-13QL, the reciprocal chimera, which similarly to Gα_i2QL could not interact with Gβγ. Moreover, Gβγ was part of tetrameric Gβγ-Gα_qQL-RGS2 and Gβγ-Gα_13-i2QL-RGS4 complexes, whereas Gα₁₃QL dissociated from Gβγ to interact with the PDZ-RhoGEF-RGS domain. Consistent with an integrated response, Gβγ and AKT kinase were associated with active SDF-1/CXCL12-stimulated P-REX1. This pathway was inhibited by Gα_qQL and Gα₁₃QL, which also prevented CXCR4-dependent cell migration. We conclude that a coordinated mechanism prioritizes Gα_q- and Gα₁₃-mediated signaling to Rho over a Gβγ-dependent Rac pathway, attributed to heterotrimeric G_i proteins.

Inhibition of mTOR Signaling and Clinical Activity of Rapamycin in Head and Neck Cancer in a Window of Opportunity Trial

PURPOSE

We studied the impact of mTOR signaling inhibition with rapamycin in head and neck squamous cell carcinoma (HNSCC) in the neoadjuvant setting. The goals were to evaluate the mTOR pathway as a therapeutic target for patients with advanced HNSCC, and the clinical safety, antitumor, and molecular activity of rapamycin administration on HNSCC.

PATIENTS AND METHODS

Patients with untreated stage II-IVA HNSCC received rapamycin for 21 days (day 1, 15 mg; days 2-12, 5 mg) prior to definitive treatment with surgery or chemoradiation. Treatment responses were assessed clinically and radiographically with CT and FDG-PET. Pre- and posttreatment biopsies and blood were obtained for toxicity, immune monitoring, and IHC assessment of mTOR signaling, as well as exome sequencing.

RESULTS

Sixteen patients (eight oral cavity, eight oropharyngeal) completed rapamycin and definitive treatment. Half of patients were p16 positive. One patient had a pathologic complete response and four (25%) patients met RECIST criteria for response (1 CR, 3 PR, 12 SD). Treatment was well tolerated with no grade 4 or unexpected toxicities. No significant immune suppression was observed. Downstream mTOR signaling was downregulated in tumor tissues as measured by phosphorylation of S6 (P < 0.0001), AKT (P < 0.0001), and 4EBP (P = 0.0361), with a significant compensatory increase in phosphorylated ERK in most patients (P < 0.001). Ki67 was reduced in tumor biopsies in all patients (P = 0.013).

CONCLUSIONS

Rapamycin treatment was well tolerated, reduced mTOR signaling and tumor growth, and resulted in significant clinical responses despite the brief treatment duration, thus supporting the potential role of mTOR inhibitors in treatment regimens for HNSCC.

GNASR201C Induces Pancreatic Cystic Neoplasms in Mice That Express Activated KRAS by Inhibiting YAP1 Signaling

BACKGROUND & AIMS

Mutations at hotspots in GNAS, which encodes stimulatory G-protein, α subunits, are detected in approximately 60% of intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. We generated mice with KRAS-induced IPMNs that also express a constitutively active form of GNAS in pancreas and studied tumor development.

METHODS

We generated p48-Cre; LSL-KrasG12D; Rosa26R-LSL-rtTA-TetO-GnasR201C mice (Kras;Gnas mice); pancreatic tissues of these mice express activated KRAS and also express a mutant form of GNAS (GNAS^R201C) upon doxycycline administration. Mice that were not given doxycycline were used as controls, and survival times were compared by Kaplan-Meier analysis. Pancreata were collected at different time points after doxycycline administration and analyzed by histology. Pancreatic ductal adenocarcinomas (PDACs) were isolated from mice and used to generate cell lines, which were analyzed by reverse transcription polymerase chain reaction, immunoblotting, immunohistochemistry, and colony formation and invasion assays. Full-length and mutant forms of yes-associated protein (YAP) were expressed in PDAC cells. IPMN specimens were obtained from 13 patients with IPMN undergoing surgery and analyzed by immunohistochemistry.

RESULTS

All Kras;Gnas mice developed pancreatic cystic lesions that resemble human IPMNs; the grade of epithelial dysplasia increased with time. None of the control mice developed cystic lesions. Approximately one third of Kras;Gnas mice developed PDACs at a median of 30 weeks after doxycycline administration, whereas 33% of control mice developed PDACs. Expression of GNAS^R201C did not accelerate the development of PDACs compared with control mice. However, the neoplasms observed in Kras;Gnas mice were more differentiated, and expressed more genes associated with ductal phenotypes, than in control mice. PDACs isolated from Kras;Gnas mice had activation of the Hippo pathway; in cells from these tumors, phosphorylated YAP1 was sequestered in the cytoplasm, and this was also observed in human IPMNs with GNAS mutations. Sequestration of YAP1 was not observed in PDAC cells from control mice.

CONCLUSIONS

In mice that express activated KRAS in the pancreas, we found expression of GNAS^R201C to cause development of more differentiated tumors, with gene expression pattern associated with the ductal phenotype. Expression of mutant GNAS caused phosphorylated YAP1 to be sequestered in the cytoplasm, altering tumor progression.

Development of a yeast-based system to identify new hBRAFV600E functional interactors

BRAFV600E is a mutant Ser-Thr protein kinase that plays a crucial role in many types of cancer, including melanoma. Despite several aspects of BRAFV600E biology have been already elucidated, the proteins that regulate its expression and activity remain largely unknown, hampering our capacity to control its unrestrained effects. Here, we propose yeast Saccharomyces cerevisiae as a model system that can be used to achieve a better understanding of the regulation of human BRAFV600E.By showing that in osmotic stress conditions hBRAFV600E can rescue the growth of strains carrying a double or triple deletion in MAPKKK belonging to the HOG pathway, we demonstrate that this oncogenic kinase is active in yeast even if it does not have an ortholog. Moreover, we report that, in the yeast ptp3∆ptc1∆ strain that is deleted in the genes encoding for two phosphatases responsible for Hog1 de-phoshorylation, hBRAFV600E mimics the toxicity observed in the presence of constitutive Hog1 activation. Finally, we exploit such a toxicity to perform a functional screening of a human cDNA library, looking for cDNAs able to rescue yeast growth. In this way, we identify SMIM10, a mitochondrial protein that in melanoma cells selectively downregulates BRAFV600E RNA and protein levels, by acting indirectly at the post-transcriptional level. Upon SMIM10 overexpression, BRAFV600E melanoma cells show disrupted mitochondrial structure/function and undergo senescence. They also show decreased ability to proliferate and form colonies, as well as increased sensitivity to the BRAF inhibitor vemurafenib. Interestingly, the analysis of TCGA melanoma samples indicates that patients with higher SMIM10 levels have a better prognosis. Therefore, these data suggest that SMIM10 exerts an oncosuppressive role in melanoma cells.Taken together, our results unveil the potential of S. cerevisiae to study hBRAFV600E, to populate the network of its functional interactors and, in doing so, to uncover new cancer-associated genes with therapeutic potential.

Correction to: mTOR co-targeting strategies for head and neck cancer therapy

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Abstract 4985: M4OC-Prevent: Clinical evaluation of metformin for oral cancer precision prevention

Despite encouraging recent results from novel treatment options, such as immunotherapy, for head and neck squamous cell carcinoma (HNSCC), limited progress has been made in improving outcomes for most patients. Prevention and early detection are key to improving the prognosis of HNSCC. We have previously shown that persistent activation of the PI3K/mTOR signaling circuitry is the most frequent dysregulated signaling mechanism in HNSCC, and that PI3K/mTOR inhibition exerts potent antitumor activity in a large series of genetically-defined and chemically-induced HNSCC models. However, potential immunosuppression and other dose-dependent side effects raise concerns regarding long term use of PI3K/mTOR inhibitors as chemopreventive agents. The repurposed drug metformin, used for frontline treatment of type 2 diabetes, decreases mTOR signaling in HPV- and HPV+ experimental HNSCC models and displays potent chemopreventive activity in mouse oral-premalignancy models. Furthermore, two recent large retrospective case-control cohort studies involving more than 300,000 diabetic patients demonstrated a decreased HNSCC risk in patients using metformin. Therefore, we conducted a single-arm, open label phase IIa clinical trial (NCT02581137) in individuals with oral premalignant lesions (OPL; oral leukoplakia or erythroplakia) to explore the potential of metformin for HNSCC prevention. Subjects were eligible if they had an OPL at any site with dysplasia or hyperplasia not associated with mechanical factors, and were otherwise healthy, without diabetes. They underwent pre- and post-treatment clinical exam of the oral cavity with lesion measurement and biopsy, along with saliva and blood collection. Eligible participants received metformin for 12 weeks (500 mg per day for the first week, 1,000 mg per day for the second week, and then 2,000 mg per day for the remaining treatment period). 26 participants were accrued and 22 were assessable for response. The toxicity profile was consistent with the known side effect profile of metformin. The clinical response rate was 18%, lower than the 30% spontaneous regression rate documented in several published long term oral leukoplakia trials. The clinical progression rate was also 18%. The significance of the clinical response assessment was limited by the short duration of treatment (only 12 weeks). Of interest, however, the histologic response rate was 59%, including 13% complete responses, and the histologic progression rate was 18%. Most of the responses consisted of a one grade improvement in histology. Circulating and tissue biomarker analyses, the latter focused on the impact of metformin on the AMPK-mTOR signaling network, are being analyzed. The goal of our studies is to provide a mechanistic framework for the selection of patients who may benefit from metformin for precision prevention of oral cancer.

Citation Format: J Silvio Gutkind, Frank G. Ondrey, Denise Laronde, Miriam Rosin, Alfredo A. Molinolo, Charles Coffey, Beverly R. Wuertz, Leigha D. Rock, Huyen Huynh, H-H. Sherry Chow, Valerie D. Butler, Scott M. Lippman, Eva Szabo. M4OC-Prevent: Clinical evaluation of metformin for oral cancer precision prevention [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4985.

Abstract 3320: Discovery and development of DNA methylation biomarkers in human papillomavirus related oropharyngeal squamous cell carcinoma

Purpose: Human papillomavirus (HPV) related oropharyngeal squamous cell carcinoma (OPSCC) has an improved prognosis compared to cancers associated with tobacco and alcohol exposure, and also exhibits a different composition of epigenetic alterations. In this methylome-wide association study, we identified DNA methylation-based biomarkers with potential utility in screening for HPV positive OPSCC. Experimental Design: In the discovery stage, genome wide DNA methylation was measured using methyl-CpG binding domain protein-enriched genome sequencing (MBD-seq) in 50 HPV positive OPSCC tissues and 25 normal tissues. We defined 51 differentially methylated regions (DMRs) with maximal methylation specificity to cancer samples. We used TCGA methylation array data to evaluate the performance of the proposed candidates. Top 20 candidates were validated using quantitative methylation specific PCR (QMSP) in independent 24 HPV related OPSCCs and 22 controls. Results: Supervised hierarchical clustering of 51 DMRs based on TCGA methylation data found that HPV positive OPSCC had significantly higher DNA methylation levels compared to normal samples and head and neck squamous cell carcinoma (HNSCC) without HPV or with different tumor sites. The methylation levels of all top 20 candidates in HPV positive OPSCC were significantly higher than those in normal samples in TCGA data. 16 of these 20 candidates were found by QMSP to have significant higher methylation levels compared with controls. 2 candidates (CCDC181 and OR6S1) had a sensitivity of 100%, while 10 candidates (KCNA3, ITGA4, BEND4, ELMO1, SFMBT2, HOXB4, ZNF439, ZNF93, VSTM2B and ZNF773) had a specificity of 100%. Our 20 candidates were found by the receiver operating characteristic analysis to have a prediction accuracy ranging from 56.3% to 99.8%. Conclusions: This study discovered 20 epigenetic markers for detection of HPV related OPSCC, which can potentially be applied to develop a population based screening test and improve disease management.

Citation Format: Shuling Ren, Daria A. Gaykalova, Theresa W. Guo, Alexander V. Favorov, Elana J. Fertig, Zubair Khan, Peter M. DeJong, Mizuo Ando, Chao Liu, Akihiro Sakai, Takahito Fukusumi, Sunny Haft, Sayed Sadat, J Silvio Gutkind, Wayne M. Koch, Joseph A. Califano. Discovery and development of DNA methylation biomarkers in human papillomavirus related oropharyngeal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3320.

Abstract 968: Targeting FAK inhibits YAP-dependent tumor growth in uveal melanoma

Activating mutations in GNAQ and GNA11 (known as GNAQ oncogenes), which encode constitutively active Gαq proteins, occur in ~90% of uveal melanoma (UM) and 4% of skin cutaneous melanoma (SKCM) respectively. UM is the most common primary cancer of the eye in adults, diagnosed in about 2,500 adults in the US every year. Approximately 50% of UM patients develop liver metastasis within 5-10 years after diagnosis, independently of the successful treatment of the primary lesions. There are effective therapeutic strategies for primary UM lesions, but UM metastatic disease is refractory to current chemotherapies and immune checkpoint inhibitors, and most patients with UM metastasis die within a year. The MEK inhibitor selumetinib has been recently approved for UM treatment, but MEK inhibition has nearly no impact on UM patient overall survival. To date, there are no effective treatment options for metastatic UM. We used bioinformatics approaches to identify systems vulnerabilities that can be exploited for UM treatment. Using the TCGA UM dataset (N=80) and SKCM samples that do not harbor Gαq genomic alterations (N=209) as control, (i) we first identified genes that are highly overexpressed in UM. We validated this approach by confirming that the genes over- and under-expressed in UM and Gαq-altered SKCM are highly overlapping (hyper-geometric p&lt;1E-198 and p&lt;1E-232 respectively). ii) We then filtered the genes for those whose inactivation leads to better patient survival in UM based on TCGA survival data. (iii) We finally used large datasets of gene essentiality and drug response screens in cancer cells to identify genes that are predicted to reduce cell viability when targeted in Gαq-expressing tumors. By filtering these genes for those that can be targeted by approved and experimental drugs (N=756), we identified 7 candidate druggable genes. Among them, the top was PTK2, which encodes a non- receptor tyrosine kinase known as FAK (focal adhesion kinase). By dissecting the Gαq signaling pathway, we found that Gαq actives FAK (p379-FAK) through a Trio-RhoA signaling pathway, independent of PLC-β regulated second messenger systems. RNA-seq of UM cells treated with a FAK inhibitor (FAKi, VS-4718) revealed that YAP gene-expression signatures were highly sensitive to FAKi. Of interest, YAP is a key regulator of cancer growth, and we have shown that YAP is highly activated by Gαq in UM, contributing to tumor growth (Cancer Cell. 2014). We found FAK regulates YAP activation by Gαq through a mechanism that involves YAP tyrosine phosphorylation on Y357. Interestingly, CRISPR-Cas9 KO of FAK and clinically relevant FAKi showed strong inhibition of UM growth in vitro and in vivo, concomitant with repression of YAP-regulated gene programs. Overall, our computational biology approach revealed that FAK may represent a novel precision therapeutic target human diseases initiated by aberrant Gαq signaling, including UM, the first identified Gαq-driven human malignancy.

Citation Format: Xiaodong Feng, Damiano Rigiracciolo, Joo-Sang Lee, Huwate Yeerna, Nadia Arang, Simone Lubrano, David D. Schlaepfer, Pablo Tamayo, Eytan Ruppin, J. Silvio Gutkind. Targeting FAK inhibits YAP-dependent tumor growth in uveal melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 968.

mTOR co-targeting strategies for head and neck cancer therapy

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy worldwide. There is an urgent need to develop effective therapeutic approaches to prevent and treat HNSCC. Recent deep sequencing of the HNSCC genomic landscape revealed a multiplicity and diversity of genetic alterations in this malignancy. Although a large variety of specific molecules were found altered in each individual tumor, they all participate in only a handful of driver signaling pathways. Among them, the PI3K/mTOR pathway is the most frequently activated, which plays a central role in cancer initiation and progression. In turn, targeting of mTOR may represent a precision therapeutic approach for HNSCC. Indeed, mTOR inhibition exerts potent anti-tumor activity in HNSCC experimental systems, and mTOR targeting clinical trials show encouraging results. However, advanced HNSCC patients may exhibit unpredictable drug resistance, and the analysis of its molecular basis suggests that co-targeting strategies may provide a more effective option. In addition, although counterintuitive, emerging evidence suggests that mTOR inhibition may enhance the anti-tumor immune response. These new findings raise the possibility that the combination of mTOR inhibitors and immune oncology agents may provide novel precision therapeutic options for HNSCC.

Unraveling the oral cancer lncRNAome: Identification of novel lncRNAs associated with malignant progression and HPV infection

OBJECTIVES

The role of long non-coding RNA (lncRNA) expression in human head and neck squamous cell carcinoma (HNSCC) is still poorly understood. In this study, we aimed at establishing the onco-lncRNAome profiling of HNSCC and to identify lncRNAs correlating with prognosis and patient survival.

MATERIALS AND METHODS

The Atlas of Noncoding RNAs in Cancer (TANRIC) database was employed to retrieve the lncRNA expression information generated from The Cancer Genome Atlas (TCGA) HNSCC RNA-sequencing data. RNA-sequencing data from HNSCC cell lines were also considered for this study. Bioinformatics approaches, such as differential gene expression analysis, survival analysis, principal component analysis, and Co-LncRNA enrichment analysis were performed.

RESULTS

Using TCGA HNSCC RNA-sequencing data from 426 HNSCC and 42 adjacent normal tissues, we found 728 lncRNA transcripts significantly and differentially expressed in HNSCC. Among the 728 lncRNAs, 55 lncRNAs were significantly associated with poor prognosis, such as overall survival and/or disease-free survival. Next, we found 140 lncRNA transcripts significantly and differentially expressed between Human Papilloma Virus (HPV) positive tumors and HPV negative tumors. Thirty lncRNA transcripts were differentially expressed between TP53 mutated and TP53 wild type tumors. Co-LncRNA analysis suggested that protein-coding genes that are co-expressed with these deregulated lncRNAs might be involved in cancer associated molecular events. With consideration of differential expression of lncRNAs in a HNSCC cell lines panel (n=22), we found several lncRNAs that may represent potential targets for diagnosis, therapy and prevention of HNSCC.

CONCLUSION

LncRNAs profiling could provide novel insights into the potential mechanisms of HNSCC oncogenesis.

The homozygous CX3CR1-M280 mutation impairs human monocyte survival

Several reports have demonstrated that mouse Cx3cr1 signaling promotes monocyte/macrophage survival. In agreement, we previously found that, in a mouse model of systemic candidiasis, genetic deficiency of Cx3cr1 resulted in increased mortality and impaired tissue fungal clearance associated with decreased macrophage survival. We translated this finding by showing that the dysfunctional CX3CR1 variant CX3CR1-M280 was associated with increased risk and worse outcome of human systemic candidiasis. However, the impact of this mutation on human monocyte/macrophage survival is poorly understood. Herein, we hypothesized that CX3CR1-M280 impairs human monocyte survival. We identified WT (CX3CR1-WT/WT), CX3CR1-WT/M280 heterozygous, and CX3CR1-M280/M280 homozygous healthy donors of European descent, and we show that CX3CL1 rescues serum starvation-induced cell death in CX3CR1-WT/WT and CX3CR1-WT/M280 but not in CX3CR1-M280/M280 monocytes. CX3CL1-induced survival of CX3CR1-WT/WT monocytes is mediated via AKT and ERK activation, which are both impaired in CX3CR1-M280/M280 monocytes, associated with decreased blood monocyte counts in CX3CR1-M280/M280 donors at steady state. Instead, CX3CR1-M280/M280 does not affect monocyte CX3CR1 surface expression or innate immune effector functions. Together, we show that homozygocity of the M280 polymorphism in CX3CR1 is a potentially novel population-based genetic factor that influences human monocyte signaling.

Activation of the orphan receptor GPR55 by lysophosphatidylinositol promotes metastasis in triple-negative breast cancer

The orphan G protein-coupled receptor GPR55 has been directly or indirectly related to basic alterations that drive malignant growth: uncontrolled cancer cell proliferation, sustained angiogenesis, and cancer cell adhesion and migration. However, little is known about the involvement of this receptor in metastasis. Here, we show that elevated GPR55 expression in human tumors is associated with the aggressive basal/triple-negative breast cancer population, higher probability to develop metastases, and therefore poor patient prognosis. Activation of GPR55 by its proposed endogenous ligand lysophosphatidylinositol confers pro-invasive features on breast cancer cells both in vitro and in vivo. Specifically, this effect is elicited by coupling to Gq/11 heterotrimeric proteins and the subsequent activation, through ERK, of the transcription factor ETV4/PEA3. Together, these data show that GPR55 promotes breast cancer metastasis, and supports the notion that this orphan receptor may constitute a new therapeutic target and potential biomarker in the highly aggressive triple-negative subtype.

Expression of an active Gαs mutant in skeletal stem cells is sufficient and necessary for fibrous dysplasia initiation and maintenance

Fibrous dysplasia (FD) is a disease caused by postzygotic activating mutations of GNAS (R201C and R201H) that encode the α-subunit of the Gs stimulatory protein. FD is characterized by the development of areas of abnormal fibroosseous tissue in the bones, resulting in skeletal deformities, fractures, and pain. Despite the well-defined genetic alterations underlying FD, whether GNAS activation is sufficient for FD initiation and the molecular and cellular consequences of GNAS mutations remains largely unresolved, and there are no currently available targeted therapeutic options for FD. Here, we have developed a conditional tetracycline (Tet)-inducible animal model expressing the GαsR201C in the skeletal stem cell (SSC) lineage (Tet-GαsR201C/Prrx1-Cre/LSL-rtTA-IRES-GFP mice), which develops typical FD bone lesions in both embryos and adult mice in less than 2 weeks following doxycycline (Dox) administration. Conditional GαsR201C expression promoted PKA activation and proliferation of SSCs along the osteogenic lineage but halted their differentiation to mature osteoblasts. Rather, as is seen clinically, areas of woven bone admixed with fibrous tissue were formed. GαsR201C caused the concomitant expression of receptor activator of nuclear factor kappa-B ligand (Rankl) that led to marked osteoclastogenesis and bone resorption. GαsR201C expression ablation by Dox withdrawal resulted in FD-like lesion regression, supporting the rationale for Gαs-targeted drugs to attempt FD cure. This model, which develops FD-like lesions that can form rapidly and revert on cessation of mutant Gαs expression, provides an opportunity to identify the molecular mechanism underlying FD initiation and progression and accelerate the development of new treatment options.

Genetically-defined novel oral squamous cell carcinoma cell lines for the development of molecular therapies

Emerging biological and translational insights from large sequencing efforts underscore the need for genetically-relevant cell lines to study the relationships between genomic alterations of tumors, and therapeutic dependencies. Here, we report a detailed characterization of a novel panel of clinically annotated oral squamous cell carcinoma (OSCC) cell lines, derived from patients with diverse ethnicity and risk habits. Molecular analysis by RNAseq and copy number alterations (CNA) identified that the cell lines harbour CNA that have been previously reported in OSCC, for example focal amplications in 3q, 7p, 8q, 11q, 20q and deletions in 3p, 5q, 8p, 18q. Similarly, our analysis identified the same cohort of frequently mutated genes previously reported in OSCC including TP53, CDKN2A, EPHA2, FAT1, NOTCH1, CASP8 and PIK3CA. Notably, we identified mutations (MLL4, USP9X, ARID2) in cell lines derived from betel quid users that may be associated with this specific risk factor. Gene expression profiles of the ORL lines also aligned with those reported for OSCC. By focusing on those gene expression signatures that are predictive of chemotherapeutic response, we observed that the ORL lines broadly clustered into three groups (cell cycle, xenobiotic metabolism, others). The ORL lines noted to be enriched in cell cycle genes responded preferentially to the CDK1 inhibitor RO3306, by MTT cell viability assay. Overall, our in-depth characterization of clinically annotated ORL lines provides new insight into the molecular alterations synonymous with OSCC, which can facilitate in the identification of biomarkers that can be used to guide diagnosis, prognosis, and treatment of OSCC.

The Next Frontier: Head and Neck Cancer Immunoprevention

Restoring T cell-mediated antitumor immunity by targeting immune checkpoint inhibitors in head and neck squamous cell carcinoma (HNSCC) results in immunomodulation and durable remissions. However, the overall response rate to these immunotherapies in HNSCC is only approximately 20%. This raises the possibility that immunologic intervention earlier in the HNSCC continuum, such as in oral premalignant lesions (OPL) could elicit an increased therapeutic response. New experimental studies suggest that immune therapies can be used for HNSCC prevention rather than therapy. Given the current excitement for precision medicine, these findings support the future development of multimodality approaches for preventive immune oncology. Cancer Prev Res; 10(12); 681-3. ©2017 AACRSee related article by Jin Wang, et al., p. 684.

The NOTCH4-HEY1 Pathway Induces Epithelial-Mesenchymal Transition in Head and Neck Squamous Cell Carcinoma

Purpose: Recently, several comprehensive genomic analyses demonstrated NOTCH1 and NOTCH3 mutations in head and neck squamous cell carcinoma (HNSCC) in approximately 20% of cases. Similar to other types of cancers, these studies also indicate that the NOTCH pathway is closely related to HNSCC progression. However, the role of NOTCH4 in HNSCC is less well understood.Experimental Design: We analyzed NOTCH4 pathway and downstream gene expression in the TCGA data set. To explore the functional role of NOTCH4, we performed in vitro proliferation, cisplatin viability, apoptosis, and cell-cycle assays. We also compared the relationships among NOTCH4, HEY1, and epithelial-mesenchymal transition (EMT)-related genes using the TCGA data set and in vitro assays.Results:HEY1 is specifically upregulated in HNSCC compared with normal tissues in the TCGA data set. NOTCH4 is more significantly related to HEY1 activation in HNSCC in comparison with other NOTCH receptors. NOTCH4 promotes cell proliferation, cisplatin resistance, inhibition of apoptosis, and cell-cycle dysregulation. Furthermore, NOTCH4 and HEY1 upregulation resulted in decreased E-cadherin expression and increased Vimentin, Fibronectin, TWIST1, and SOX2 expression. NOTCH4 and HEY1 expression was associated with an EMT phenotype as well as increased invasion and cell migration.Conclusions: In HNSCC, the NOTCH4-HEY1 pathway is specifically upregulated, induces proliferation and cisplatin resistance, and promotes EMT. Clin Cancer Res; 24(3); 619-33. ©2017 AACR.

Genetic variants affecting equivalent protein family positions reflect human diversity

Members of diverse protein families often perform overlapping or redundant functions meaning that different variations within them could reflect differences between individual organisms. We investigated likely functional positions within aligned protein families that contained a significant enrichment of nonsynonymous variants in genomes of healthy individuals. We identified more than a thousand enriched positions across hundreds of family alignments with roles indicative of mammalian individuality, including sensory perception and the immune system. The most significant position is the Arginine from the Olfactory receptor “DRY” motif, which has more variants in healthy individuals than all other positions in the proteome. Odorant binding data suggests that these variants lead to receptor inactivity, and they are mostly mutually exclusive with other loss-of-function (stop/frameshift) variants. Some DRY Arginine variants correlate with smell preferences in sub-populations and all 2,504 humans studied contain a unique spectrum of active and inactive receptors. The many other variant enriched positions, across hundreds of other families might also provide insights into individual differences.

A Novel Functional Splice Variant of AKT3 Defined by Analysis of Alternative Splice Expression in HPV-Positive Oropharyngeal Cancers

The incidence of HPV-related oropharyngeal squamous cell carcinoma (OPSCC) has increased more than 200% in the past 20 years. Recent genetic sequencing efforts have elucidated relevant genes in head and neck cancer, but HPV-related tumors have consistently shown few DNA mutations. In this study, we sought to analyze alternative splicing events (ASE) that could alter gene function independent of mutations. To identify ASE unique to HPV-related tumors, RNA sequencing was performed on 46 HPV-positive OPSCC and 25 normal tissue samples. A novel algorithm using outlier statistics on RNA-sequencing junction expression identified 109 splicing events, which were confirmed in a validation set from The Cancer Genome Atlas. Because the most common type of splicing event identified was an alternative start site (39%), MBD-seq genome-wide CpG methylation data were analyzed for methylation alterations at promoter regions. ASE in six genes showed significant negative correlation between promoter methylation and expression of an alternative transcriptional start site, including AKT3 The novel AKT3 transcriptional variant and methylation changes were confirmed using qRT-PCR and qMSP methods. In vitro silencing of the novel AKT3 variant resulted in significant growth inhibition of multiple head and neck cell lines, an effect not observed with wild-type AKT3 knockdown. Analysis of ASE in HPV-related OPSCC identified multiple alterations likely involved in carcinogenesis, including a novel, functionally active transcriptional variant of AKT3 Our data indicate that ASEs represent a significant mechanism of oncogenesis with untapped potential for understanding complex genetic changes that result in the development of cancer. Cancer Res; 77(19); 5248-58. ©2017 AACR.

Genetic evidence that β-arrestins are dispensable for the initiation of β2-adrenergic receptor signaling to ERK

The β₂-adrenergic receptor (β₂AR) has provided a paradigm to elucidate how G protein-coupled receptors (GPCRs) control intracellular signaling, including the discovery that β-arrestins, which bind to ligand-activated GPCRs, are central for GPCR function. We used genome editing, conditional gene deletion, and small interfering RNAs (siRNAs) to determine the roles of β-arrestin 1 (β-arr1) and β-arr2 in β₂AR internalization, trafficking, and signaling to ERK. We found that only β-arr2 was essential for β₂AR internalization. Unexpectedly, β-arr1 and β-arr2 and receptor internalization were dispensable for ERK activation. Instead, β₂AR signaled through Gα_s and Gβγ subunits through a pathway that involved the tyrosine kinase SRC, the adaptor protein SHC, the guanine nucleotide exchange factor SOS, the small GTPase RAS, and the kinases RAF and MEK, which led to ERK activation. These findings provide a molecular framework for β₂AR signaling through β-arrestin-independent pathways in key physiological functions and under pathological conditions.