Progressive tumor formation in mice with conditional deletion of TGF-beta signaling in head and neck epithelia is associated with activation of the PI3K/Akt pathway

TGFβ signaling inhibits goblet cell differentiation via SPDEF in conjunctival epithelium

The ocular surface epithelia, including the stratified but non-keratinized corneal, limbal and conjunctival epithelium, in concert with the epidermal keratinized eyelid epithelium, function together to maintain eye health and vision. Abnormalities in cellular proliferation or differentiation in any of these surface epithelia are central in the pathogenesis of many ocular surface disorders. Goblet cells are important secretory cell components of various epithelia, including the conjunctiva; however, mechanisms that regulate goblet cell differentiation in the conjunctiva are not well understood. Herein, we report that conditional deletion of transforming growth factor β receptor II (Tgfbr2) in keratin 14-positive stratified epithelia causes ocular surface epithelial hyperplasia and conjunctival goblet cell expansion that invaginates into the subconjunctival stroma in the mouse eye. We found that, in the absence of an external phenotype, the ocular surface epithelium develops properly, but young mice displayed conjunctival goblet cell expansion, demonstrating that TGFβ signaling is required for normal restriction of goblet cells within the conjunctiva. We observed increased expression of SAM-pointed domain containing ETS transcription factor (SPDEF) in stratified conjunctival epithelial cells in Tgfbr2 cKO mice, suggesting that TGFβ restricted goblet cell differentiation directly by repressing Spdef transcription. Gain of function of Spdef in keratin 14-positive epithelia resulted in the ectopic formation of goblet cells in the eyelid and peripheral cornea in adult mice. We found that Smad3 bound two distinct sites on the Spdef promoter and that treatment of keratin 14-positive cells with TGFβ inhibited SPDEF activation, thereby identifying a novel mechanistic role for TGFβ in regulating goblet cell differentiation.

Follistatin is induced by ionizing radiation and potentially predictive of radiosensitivity in radiation-induced fibrosis patient derived fibroblasts

Follistatin is a potent regulator of the inflammatory response and binds to and inhibits activin A action. Activin A is a member of the TGFβ protein superfamily which has regulatory roles in the inflammatory response and in the fibrotic process. Fibrosis can occur following cell injury and cell death induced by agents such as ionizing radiation (IR). IR is used to treat cancer and marked fibrotic response is a normal tissue (non-tumour) consequence in a fraction of patients under the current dose regimes. The discovery and development of a therapeutic to abate fibrosis in these radiosensitive patients would be a major advance for cancer radiotherapy. Likewise, prediction of which patients are susceptible to fibrosis would enable individualization of treatment and provide an opportunity for pre-emptive fibrosis control and better tumour treatment outcomes. The levels of activin A and follistatin were measured in fibroblasts derived from patients who developed severe radiation-induced fibrosis following radiotherapy and compared to fibroblasts from patients who did not. Both follistatin and activin A gene expression levels were increased following IR and the follistatin gene expression level was lower in the fibroblasts from fibrosis patients compared to controls at both basal levels and after IR. The major follistatin transcript variants were found to have a similar response to IR and both were reduced in fibrosis patients. Levels of follistatin and activin A secreted in the fibroblast culture medium also increased in response to IR and the relative follistatin protein levels were significantly lower in the samples derived from fibrosis patients. The decrease in the follistatin levels can lead to an increased bioactivity of activin A and hence may provide a useful measurement to identify patients at risk of a severe fibrotic response to IR. Additionally, follistatin, by its ability to neutralise the actions of activin A may be of value as an anti-fibrotic for radiation induced fibrosis.

Inhibition of mTOR reduces anal carcinogenesis in transgenic mouse model

The molecular mechanism of human anal squamous cell carcinoma (ASCC) is unclear, and the accumulating evidence indicate association of ASCC with the activation of the Akt/mTOR pathway. Here we describe a mouse model with spontaneous anal squamous cell cancer, wherein a combined deletion of Tgfbr1 and Pten in stratified squamous epithelia was induced using inducible K14-Cre. Histopathologic analyses confirmed that 33.3% of the mice showed increased susceptibility to ASCC and precancerous lesions. Biomarker analyses demonstrated that the activation of the Akt pathway in ASCC of the Tgfbr1 and Pten double knockout (2cKO) mouse was similar to that observed in human anal cancer. Chemopreventive experiments using mTOR inhibitor-rapamycin treatment significantly delayed the onset of the ASCC tumors and reduced the tumor burden in 2cKO mice by decreasing the phosphorylation of Akt and S6. This is the first conditional knockout mouse model used for investigating the contributions of viral and cellular factors in anal carcinogenesis without carcinogen-mediated induction, and it would provide a platform for assessing new therapeutic modalities for treating and/or preventing this type of cancer.

Simultaneous activation of Kras and inactivation of p53 induces soft tissue sarcoma and bladder urothelial hyperplasia

The development of the Cre recombinase-controlled (Cre/LoxP) technique allows the manipulation of specific tumorigenic genes, temporarily and spatially. Our original intention of this study was to investigate the role of Kras and p53 in the development of urinary bladder cancer. First, to validate the effect of intravesical delivery on Cre recombination (Adeno-Cre), we examined activity and expression of β-galactosidase in the bladder of control ROSA transgenic mice. The results confirmed specific recombination as evidenced by β-galactosidase activity in the bladder urothelium of these mice. Then, we administered the same adenovirus into the bladder of double transgenic Kras^LSLG12D/+. p53^fl/fl mice. The virus solution was held in place by a distal urethral retention suture for 2 hours. To our surprise, there was a rapid development of a spindle-cell tumor with sarcoma characteristics near the suture site, within the pelvic area but outside the urinary track. Since we did not see any detectable β-galactosidase in the area outside of the bladder in the validating (control) experiment, we interpreted that this sarcoma formation was likely due to transduction by Adeno-Cre in the soft tissue of the suture site. To avoid the loss of skin integrity associated with the retention suture, we transitioned to an alternative technique without suture to retain the Adeno-Cre into the bladder cavity. Interestingly, although multiple Adeno-Cre treatments were applied, only urothelial hyperplasia but not carcinogenesis was observed in the subsequent experiments of up to 6 months. In conclusion, we observed that the simultaneous inactivation of p53 and activation of Kras induces quick formation of spindle-cell sarcoma in the soft tissues adjacent to the bladder but slow formation of urothelial hyperplasia inside the bladder. These results strongly suggest that the effect of oncogene regulation to produce either hyperplasia or carcinogenesis greatly depends on the tissue type.

Signaling Networks of Activated Oncogenic and Altered Tumor Suppressor Genes in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) arises from the upper aerodigestive tract and is the six most common cancers worldwide. HNSCC is associated with high morbidity and mortality, as standard surgery, radiation, and chemotherapy can cause significant disfigurement and only provide 5-year survival rates of ~50-60%. The heterogeneity of HNSCC subsets with different potentials for recurrence and metastasis challenges the traditional pathological classification system, thereby increasing demand for the development of new diagnostic, prognostic, and therapeutic tools based on global molecular signatures of HNSCC. Historically, using classical biological techniques, it has been extremely difficult and time-consuming to survey hundreds or thousands of genes in a given disease. However, the development of high throughput technologies and high-powered computation throughout the last two decades has enabled us to investigate hundreds or thousands of genes simultaneously. Using high throughput technologies, our laboratory has identified the gene signatures and protein networks, which significantly affect HNSCC malignant phenotypes, including TP53/p63/p73 family members, IL-1/TNF-β/NF-κB, PI3K/AKT/mTOR, IL-6/IL-6R/JAK/STAT3, EGFR/MAPK/AP1, HGF/cMET/EGR1, and TGFβ/TGFβR/TAK1/SMAD pathways. This review summarizes the results from high-throughput technological assays conducted on HNSCC samples, including microarray, DNA methylation, miRNA profiling, and protein array, using primarily experimental data and conclusions generated in our own laboratory. The use of bioinformatics and integrated analyses of data sets from different platforms, as well as meta-analysis of large datasets pulled from multiple publicly available studies, provided significantly higher statistical power to extract biologically relevant information. The data suggested that the heterogeneity of HNSCC genotype and phenotype are much more complex than we previously thought. Understanding of global molecular signatures and disease classification for specific subsets of HNSCC will be essential to provide accurate diagnoses for targeted therapy and personalized treatment, which is an important effort toward improving patient outcomes.

PI3K/mTOR inhibitor PF-04691502 antitumor activity is enhanced with induction of wild-type TP53 in human xenograft and murine knockout models of head and neck cancer

PURPOSE

Phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway activation is often associated with altered expression or mutations of PIK3CA, TP53/p73, PTEN, and TGF-β receptors (TGFBR) in head and neck squamous cell carcinomas (HNSCC). However, little is known about how these alterations affect response to PI3K/mTOR-targeted agents.

EXPERIMENTAL DESIGN

In this preclinical study, PI3K/Akt/mTOR signaling was characterized in nine HNSCC (UM-SCC) cell lines and human oral keratinocytes. We investigated the molecular and anticancer effects of dual PI3K/mTOR inhibitor PF-04691502(PF-502) in UM-SCC expressing PIK3CA with decreased wild-type TP53, mutant TP53-/+ mutantTGFBR2, and in HNSCC of a conditional Pten/Tgfbr1 double knockout mouse model displaying PI3K/Akt/mTOR activation.

RESULTS

UM-SCC showed increased PIK3CA expression and Akt/mTOR activation, and PF-502 inhibited PI3K/mTORC1/2 targets. In human HNSCC expressing PIK3CA and decreased wtTP53 and p73, PF-502 reciprocally enhanced TP53/p73 expression and growth inhibition, which was partially reversible by p53 inhibitor pifithrin-α. Most UM-SCC with wtTP53 exhibited a lower IC50 than those with mtTP53 status. PF-502 blocked growth in G0-G1 and increased apoptotic sub-G0 DNA. PF-502 suppressed tumorigenesis and showed combinatorial activity with radiation in a wild-type TP53 UM-SCC xenograft model. PF-502 also significantly delayed HNSCC tumorigenesis and prolonged survival of Pten/Tgfbr1-deficient mice. Significant inhibition of p-Akt, p-4EBP1, p-S6, and Ki67, as well as increased p53 and TUNEL were observed in tumor specimens.

CONCLUSIONS

PI3K-mTOR inhibition can enhance TP53/p73 expression and significantly inhibit tumor growth alone or when combined with radiation in HNSCC with wild-type TP53. PIK3CA, TP53/p73, PTEN, and TGF-β alterations are potential modifiers of response and merit investigation in future clinical trials with PI3K-mTOR inhibitors.

Transforming Growth Factor Beta Signaling in Cutaneous Wound Healing: Lessons Learned from Animal Studies

SIGNIFICANCE

Wound healing is a complex physiological process involving a multitude of growth factors, among which transforming growth factor beta (TGF-β) has the broadest spectrum of effects. Animal studies have provided key information on the mechanisms of TGF-β action in wound healing and have guided the development of therapeutic strategies targeting the TGF-β pathway to improve wound healing and scarring outcome.

RECENT ADVANCES

Development of tissue-specific expression systems for overexpression or knockout of TGF-β signaling pathway components has led to novel insight into the role of TGF-β signaling in wound healing. This work has also identified molecules that might serve as molecular targets for the treatment of pathological skin conditions such as chronic wounds and excessive scarring (fibrosis).

CRITICAL ISSUES

Many of the mouse models with genetic alterations in the TGF-β signaling pathway develop an underlying skin abnormality, which may pose some limitations on the interpretation of wound-healing results obtained in these animals. Also, TGF-β's pleiotropic effects on many cell types throughout all phases of wound healing present a challenge in designing specific strategies for targeting the TGF-β signaling pathway to promote wound healing or reduce scarring.

FUTURE DIRECTIONS

Further characterization of TGF-β signaling pathway components using inducible tissue-specific overexpression or knockout technology will be needed to corroborate results obtained in mouse models that display a skin phenotype, and to better understand the role of TGF-β signaling during distinct phases of the wound-healing process. Such studies will also provide a better understanding of how TGF-β mediates its autocrine, paracrine, and double paracrine effects on cellular responses in vivo during wound healing.

miR-211 promotes the progression of head and neck carcinomas by targeting TGFβRII

miR-211 up-regulation and transforming growth factor-β type II receptor (TGFβRII) down-regulation are associated with poor prognosis of head and neck squamous cell carcinoma (HNSCC). miR-211 directly targets TGFβRII with the miR-211-TGFβRII-c-Myc axis promoting HNSCC progression. An inverse correlation of miR-211 and TGFβRII expression was found in metastatic HNSCC samples. After 4-nitroquinoline 1-oxide induction, more severe epithelial tumorigenesis was detected on K14-miR-211 transgenic mouse dorsal tongues. Human metastatic lesions and mouse tongue tumors showed increased nuclear c-Myc expression. A novel role for miR-211 in the regulation of TGFβRII and c-Myc during tumorigenesis being revealed should help to develop anti-HNSCC therapies.

TGF-β and NF-κB signal pathway cross-talk is mediated through TAK1 and SMAD7 in a subset of head and neck cancers

Transforming growth factor-beta (TGF-β) has a dual role in epithelial malignancies, including head and neck squamous cell carcinoma (HNSCC). Attenuation of canonical TGF-β signaling enhances de novo tumor development, whereas TGF-β overexpression and signaling paradoxically promotes malignant progression. We recently observed that TGF-β-induced growth arrest response is attenuated, in association with aberrant activation of nuclear factor-κB (NF-κB), a transcription factor, which promotes malignant progression in HNSCC. However, what role cross-talk between components of the TGF-β and NF-κB pathways plays in altered activation of these pathways has not been established. Here, we show TGF-β receptor II and TGF-β-activated kinase 1 (TAK1) are predominantly expressed in a subset of HNSCC tumors with nuclear activation of NF-κB family member RELA (p65). Further, TGF-β1 treatment induced sequential phosphorylation of TAK1, IKK, IκBα and RELA in human HNSCC lines. TAK1 enhances TGF-β-induced NF-κB activation, as TAK1 siRNA knockdown decreased TGF-β1-induced phosphorylation of IKK, IκB and RELA, degradation of IκBα, RELA nuclear translocation and DNA binding, and NF-κB-induced reporter and target gene transcription. Functionally, TAK1 siRNA inhibited cell proliferation, migration and invasion. Celastrol, a TAK1 inhibitor and anti-inflammatory compound used in traditional Chinese medicine, also decreased TGF-β1-induced phosphorylation of TAK1 and RELA, and suppressed basal, TGF-β1- and tumor necrosis factor-alpha (TNF-α)-induced NF-κB reporter gene activity. Celastrol also inhibited cell proliferation, while increasing sub-G0 DNA fragmentation and Annexin V markers of apoptosis. Furthermore, TGF-β and RELA activation promoted SMAD7 expression. In turn, SMAD7 preferentially suppressed TGF-β-induced SMAD and NF-κB reporters when compared with constitutive or TNF-α-induced NF-κB reporter gene activation. Thus, cross-talk by TGF-β via TAK1 and NF-κB promotes the malignant phenotype of HNSCC. Moreover, NF-κB may contribute to the downstream attenuation of canonical TGF-β signaling through increased SMAD7 expression. Celastrol highlights the therapeutic potential of agents targeting TAK1 as a key node in this pro-oncogenic TGF-β-NF-κB signal pathway.

MicroRNA-135b acts as a tumor promoter by targeting the hypoxia-inducible factor pathway in genetically defined mouse model of head and neck squamous cell carcinoma

Here in, we investigated the mechanism underlying overexpression of miR-135b in the human head and neck squamous cell carcinoma (HNSCC) cell lines and in the HNSCC mouse model. Exogenous expression of miR-135b in these cell lines increased cell proliferation, migration, and colony formation. Gene silencing analysis revealed that miR-135b affects a regulator that inhibits hypoxia-inducible factor (HIF). Increased miR-135b expression was positively correlated with HIF-1α expression and microvessel density in the HNSCC model. Thus, our data demonstrate that miR-135b acts as a tumor promoter by promoting cancer cell proliferation, colony formation, survival, and angiogenesis through activation of HIF-1α in HNSCC.

The Role of TGFβ Signaling in Squamous Cell Cancer: Lessons from Mouse Models

TGFβ1 is a member of a large growth factor family including activins/inhibins and bone morphogenic proteins (BMPs) that have a potent growth regulatory and immunomodulatory functions in normal skin homeostasis, regulation of epidermal stem cells, extracellular matrix production, angiogenesis, and inflammation. TGFβ signaling is tightly regulated in normal tissues and becomes deregulated during cancer development in cutaneous SCC and many other solid tumors. Because of these diverse biological processes regulated by TGFβ1, this cytokine and its signaling pathway appear to function at multiple points during carcinogenesis with distinct effects. The mouse skin carcinogenesis model has been a useful tool to dissect the function of this pathway in cancer pathogenesis, with transgenic and null mice as well as small molecule inhibitors to alter the function of the TGFβ1 pathway and assess the effects on cancer development. This paper will review data on changes in TGFβ1 signaling in human SCC primarily HNSCC and cutaneous SCC and different mouse models that have been generated to investigate the relevance of these changes to cancer. A better understanding of the mechanisms underlying the duality of TGFβ1 action in carcinogenesis will inform potential use of this signaling pathway for targeted therapies.

Differential response of epithelial stem cell populations in hair follicles to TGF-β signaling

Epidermal stem cells residing in different locations in the skin continuously self-renew and differentiate into distinct cell lineages to maintain skin homeostasis during postnatal life. Murine epidermal stem cells located at the bulge region are responsible for replenishing the hair lineage, while the stem cells at the isthmus regenerate interfollicular epidermis and sebaceous glands. In vitro cell culture and in vivo animal studies have implicated TGF-β signaling in the maintenance of epidermal and hair cycle homeostasis. Here, we employed a triple transgenic animal model that utilizes a combined Cre/loxP and rtTA/TRE system to allow inducible and reversible inhibition of TGF-β signaling in hair follicle lineages and suprabasal layer of the epidermis. Using this animal model, we have analyzed the role of TGF-β signaling in distinct phases of the hair cycle. Transient abrogation of TGF-β signaling does not prevent catagen progression; however, it induces aberrant proliferation and differentiation of isthmus stem cells to epidermis and sebocyte lineages and a blockade in anagen re-entry as well as results in an incomplete hair shaft development. Moreover, ablation of TGF-β signaling during anagen leads to increased apoptosis in the secondary hair germ and bulb matrix cells. Blocking of TGF-β signaling in bulge stem cell cultures abolishes their colony-forming ability, suggesting that TGF-β signaling is required for the maintenance of bulge stem cells. At the molecular level, inhibition of TGF-β signaling results in a decrease in both Lrig1-expressing isthmus stem cells and Lrg5-expressing bulge stem cells, which may account for the phenotypes seen in our animal model. These data strongly suggest that TGF-β signaling plays an important role in regulating the proliferation, differentiation, and apoptosis of distinct epithelial stem cell populations in hair follicles.

Chemopreventive and chemotherapeutic actions of mTOR inhibitor in genetically defined head and neck squamous cell carcinoma mouse model

PURPOSE

To assess the efficacy of rapamycin treatment in chemoprevention and chemotherapy of tumorigenesis in a genetically defined mouse model of head and neck squamous cell carcinoma (HNSCC).

EXPERIMENTAL DESIGN

Knockdown of Tgfbr1 and/or Pten using siRNA-mediated RNA interference was carried out in human HNSCC cell lines to analyze molecular changes in the mTOR pathway. Tgfbr1(flox/flox); Pten(flox/flox); K14-CreER(tam) mice were treated with oral gavage of tamoxifen for the conditional deletion of Tgfbr1 and Pten in oral mucosa, resulting in HNSCC. Tgfbr1 and Pten conditonal deletion (2cKO) mice were treated with rapamycin before or after the onset of HNSCC, and the efficacy of this treatment was assessed by determining tumor burden, longevity, and molecular analysis of the mTOR pathway. Molecular changes observed in human HNSCC cell lines and 2cKO mice were compared to identify key alterations in the mTOR pathway.

RESULTS

Knockdown of Tgfbr1 and/or Pten in human HNSCC cell lines resulted in activation of mTOR activity complex 1 and increased levels of survivin. Furthermore, we observed similar changes in HNSCC of the 2cKO mouse. In the human HNSCC tissue array, a loss of Tgfbr1 expression correlated with increased survivin levels. Chemopreventive rapamycin treatment significantly delayed the onset of the HNSCC tumors and prolonged survival in 2cKO mice. In addition, we also found that rapamycin had a therapeutic effect on squamous cell carcinomas in these mice. In 2cKO HNSCC tongue tumors, rapamycin treatment induced apoptosis, inhibited cell proliferation and phosphorylation of Akt and S6, and decreased survivin expression.

CONCLUSIONS

These findings indicate that tumorigenesis in 2cKO HNSCC is associated with activation of the Akt/mTOR/survivin pathway, and inhibition of this pathway by rapamycin treatment successfully ameliorates the onset and progression of tumorigenesis.

Transforming growth factor β and Ras/MEK/ERK signaling regulate the expression level of a novel tumor suppressor Lefty

OBJECTIVES

The objectives of the present study were (i) to identify a novel tumor suppressor gene whose expression level was regulated by transforming growth factor (TGF-β) and (ii) to evaluate the effect of Ras/MEK/ERK signaling on TGF-β-dependent Lefty up-regulation.

METHODS

Human pancreatic cancer cell lines were used. The effect of Ras/MEK/ERK pathway on TGF-β-mediated Lefty up-regulation was tested by adding K-ras small interfering RNA, MEK inhibitor U0126, or extracellular signal-regulated kinase (ERK) inhibitor LY294002.

RESULTS

Transforming growth factor β upregulated Lefty messenger RNA levels within 6 of the 7 cell lines. Lefty exerts an antagonistic effect against the tumor-promoting molecule, Nodal, as recombinant Lefty suppressed Nodal-mediated proliferation. Interestingly, inhibition of the Ras/MEK/ERK pathway dramatically enhanced TGF-mediated Lefty up-regulation, suggesting that Ras/MEK/ERK signaling suppresses TGF-β-Lefty pathway.

CONCLUSIONS

Our data suggest that Lefty is a novel TGF-β target molecule that mediates growth inhibition of pancreatic cancer cells. In addition, activation of the Ras/MEK/ERK pathway serves as a mechanism by which pancreatic cancer escapes from growth inhibition by the TGF-β-Lefty axis. The results imply a novel therapeutic strategy for pancreatic cancer, that is, combination treatment with Ras/MEK/ERK inhibitors and TGF-β.

Comparative analysis of algorithms for integration of copy number and expression data

Chromosomal instability is a hallmark of cancer, and genes that display abnormal expression in aberrant chromosomal regions are likely to be key players in tumor progression. Identifying such driver genes reliably requires computational methods that can integrate genome-scale data from several sources. We compared the performance of ten algorithms that integrate copy-number and transcriptomics data from 15 head and neck squamous cell carcinoma cell lines, 129 lung squamous cell carcinoma primary tumors and simulated data. Our results revealed clear differences between the methods in terms of sensitivity and specificity as well as in their performance in small and large sample sizes. Results of the comparison are available at http://csbi.ltdk.helsinki.fi/cn2gealgo/.

Lung cancer-derived galectin-1 enhances tumorigenic potentiation of tumor-associated dendritic cells by expressing heparin-binding EGF-like growth factor

The interaction between cancer cells and their microenvironment is a vicious cycle that enhances the survival and progression of cancer, resulting in metastasis. This study is the first to indicate that lung cancer-derived galectin-1 secretion is responsible for stimulating tumor-associated dendritic cells (TADCs) production of mature heparin-binding EGF-like growth factor (HB-EGF), which, in turn, increases cancer progression. Treatment of galectin-1, present in large amounts in lung cancer conditioned medium and lung cancer patient sera, mimicked the inductive effect of lung cancer conditioned medium on the expression and ectodomain shedding of HB-EGF by TNFα-converting enzyme/a disintegrin and metalloproteinase 9 (ADAM9) and ADAM17. Significant up-regulation of HB-EGF has been seen in tumor-infiltrating CD11c(+) dendritic cells in human lung cancer samples. Active cleavage of HB-EGF in TADCs by ADAM9 and ADAM17 is associated with increased protein kinase C δ and Lyn signaling. Enhancement of HB-EGF production in TADCs increased the proliferation, migration, and epithelial-to-mesenchymal transition abilities of lung cancer. In contrast, inhibiting HB-EGF by siRNA suppressed TADC-mediated cancer progression. Moreover, mice injected with galectin-1 knockdown Lewis lung carcinoma showed decreased expression and ectodomain shedding of HB-EGF and reduced incidence of cancer development, resulting in increased survival rates. We demonstrate here for the first time that human and mouse DCs are a source of HB-EGF, an EGFR ligand with tumorigenic properties. Antagonists of the effect of lung cancer-derived galectin-1 on DCs and anti-HB-EGF blocking antibodies could, therefore, have therapeutic potential as antitumor agents.

Loss of TGF-β signaling and PTEN promotes head and neck squamous cell carcinoma through cellular senescence evasion and cancer-related inflammation

The molecular mechanisms that contribute to the initiation and progression of head and neck squamous cell carcinoma (HNSCC) have not been completely delineated. Our observations indicate that defects in the transforming growth factor-β and PI3K/Akt signaling pathways are common in human HNSCCs. Conditional activation of the PI3K/Akt pathway due to Pten deletion in the mouse head and neck epithelia gives rise to hyperproliferation, but only a few lesions progress to HNSCC. However, Pten-deficient mice developed full-penetrance HNSCC in combination with type I TGF-β receptor (Tgfbr1) deletion. Molecular analysis revealed enhanced cell proliferation, decreased apoptosis, and increased expression of CCND1 in the basal layer of the head and neck epithelia, as well as in the tumors of Tgfbr1/Pten double conditional knockout (2cKO) mice. Furthermore, neoplastic transformation involves senescence evasion, and is associated with an increased number of putative cancer stem cells. In addition, the nuclear factor-κB pathway activation, myeloid-derived suppressor cell infiltration, angiogenesis and immune suppression in the tumor microenvironment, all of which are characteristics of human HNSCCs, contribute significantly to head and neck carcinogenesis in 2cKO mice. These tumors display pathology and multiple molecular alterations resembling human HNSCCs. This suggests that the Tgfbr1/Pten 2cKO mouse model is suitable for preclinical intervention, and that it has significant implications in the development of diagnostic cancer biomarkers and effective strategies for prevention and treatment of HNSCCs.

Therapeutic targets in head and neck squamous cell carcinoma: identification, evaluation, and clinical translation

Head and neck squamous cell carcinoma (HNSCC) encompasses a diverse group of malignancies originating in the oral cavity, oropharynx, larynx and hypopharynx. Although treatment modalities have improved, carefully designed biomarker-driven clinical trials will yield the best opportunities to enhance HNSCC therapy options in the future. Due to the heterogeneous nature of HNSCC, discovering a "silver bullet" for the treatment of HNSCC is unlikely. Consequently, impactful HNSCC clinical trials will require multiple assay platforms and expanded technical expertise. In this review, we will outline pathways critical to HNSCC oncogenesis and highlight signaling nodes within these pathways that represent biomarkers for prognosis and potential targeted therapies. All treatment modalities are subject to mechanisms of resistance; thus, lessons learned from HNSCC investigations and studies of similar targeted agents in other pertinent malignancies will be discussed.

Deconstructing the mechanisms and consequences of TGF-β-induced EMT during cancer progression

Transforming growth factor-β (TGF-β) is a potent pleiotropic cytokine that regulates mammalian development, differentiation, and homeostasis in essentially all cell types and tissues. TGF-β normally exerts anticancer activities by prohibiting cell proliferation and by creating cell microenvironments that inhibit cell motility, invasion, and metastasis. However, accumulating evidence indicates that the process of tumorigenesis, particularly that associated with metastatic progression, confers TGF-β with oncogenic activities, a functional switch known as the "TGF-β paradox." The molecular determinants governing the TGF-β paradox are complex and represent an intense area of investigation by researchers in academic and industrial settings. Recent findings link genetic and epigenetic events in mediating the acquisition of oncogenic activity by TGF-β, as do aberrant alterations within tumor microenvironments. These events coalesce to enable TGF-β to direct metastatic progression via the stimulation of epithelial-mesenchymal transition (EMT), which permits carcinoma cells to abandon polarized epithelial phenotypes in favor of apolar mesenchymal-like phenotypes. Attempts to deconstruct the EMT process induced by TGF-β have identified numerous signaling molecules, transcription factors, and microRNAs operant in mediating the initiation and resolution of this complex transdifferentiation event. In addition to its ability to enhance carcinoma cell invasion and metastasis, EMT also endows transitioned cells with stem-like properties, including the acquisition of self-renewal and tumor-initiating capabilities coupled to chemoresistance. Here, we review recent findings that delineate the pathophysiological mechanisms whereby EMT stimulated by TGF-β promotes metastatic progression and disease recurrence in human carcinomas.

Role of Smads in TGFβ signaling

Transforming growth factor-β (TGFβ) is the prototype for a large family of pleiotropic factors that signal via heterotetrameric complexes of type I and type II serine/threonine kinase receptors. Important intracellular mediators of TGFβ signaling are members of the Smad family. Smad2 and 3 are activated by C-terminal receptor-mediated phosphorylation, whereafter they form complexes with Smad4 and are translocated to the nucleus where they, in cooperation with other transcription factors, co-activators and co-repressors, regulate the transcription of specific genes. Smads have key roles in exerting TGFβ-induced programs leading to cell growth arrest and epithelial-mesenchymal transition. The activity and stability of Smad molecules are carefully regulated by a plethora of post-translational modifications, including phosphorylation, ubiquitination, sumoylation, acetylation and poly(ADP)-ribosylation. The Smad function has been shown to be perturbed in certain diseases such as cancer.

Pharmacologic inhibition of ALK5 causes selective induction of terminal differentiation in mouse keratinocytes expressing oncogenic HRAS

TGFβ has both tumor suppressive and oncogenic roles in cancer development. We previously showed that SB431542 (SB), a small molecule inhibitor of the TGFβ type I receptor (ALK5) kinase, suppressed benign epidermal tumor formation but enhanced malignant conversion. Here, we show that SB treatment of primary K5rTA/tetORASV12G bitransgenic keratinocytes did not alter HRASV12G-induced keratinocyte hyperproliferation. However, continuous SB treatment significantly enhanced HRASV12G-induced cornified envelope formation and cell death linked to increased expression of enzymes transglutaminase (TGM) 1 and TGM3 and constituents of the cornified envelope small proline-rich protein (SPR) 1A and SPR2H. In contrast, TGFβ1 suppressed cornified envelope formation in HRASV12G keratinocytes. Similar results were obtained in HRASV12G transgenic mice treated topically with SB or by coexpressing TGFβ1 and HRASV12G in the epidermis. Despite significant cell death, SB-resistant HRASV12G keratinocytes repopulated the primary culture that had overcome HRas-induced senescence. These cells expressed reduced levels of p16(ink4a) and were growth stimulated by SB but remained sensitive to a calcium-induced growth arrest. Together these results suggest that differential responsiveness to cornification may represent a mechanism by which pharmacologic blockade of TGFβ signaling can inhibit the outgrowth of preneoplastic lesions but may cause a more progressed phenotype in a separate keratinocyte population.

Multiple self-healing squamous epithelioma is caused by a disease-specific spectrum of mutations in TGFBR1

Multiple self-healing squamous epithelioma (MSSE), also known as Ferguson-Smith disease (FSD), is an autosomal-dominant skin cancer condition characterized by multiple squamous-carcinoma-like locally invasive skin tumors that grow rapidly for a few weeks before spontaneously regressing, leaving scars. High-throughput genomic sequencing of a conservative estimate (24.2 Mb) of the disease locus on chromosome 9 using exon array capture identified independent mutations in TGFBR1 in three unrelated families. Subsequent dideoxy sequencing of TGFBR1 identified 11 distinct monoallelic mutations in 18 affected families, firmly establishing TGFBR1 as the causative gene. The nature of the sequence variants, which include mutations in the extracellular ligand-binding domain and a series of truncating mutations in the kinase domain, indicates a clear genotype-phenotype correlation between loss-of-function TGFBR1 mutations and MSSE. This distinguishes MSSE from the Marfan syndrome-related disorders in which missense mutations in TGFBR1 lead to developmental defects with vascular involvement but no reported predisposition to cancer.

Use of a TGFbeta type I receptor inhibitor in mouse skin carcinogenesis reveals a dual role for TGFbeta signaling in tumor promotion and progression

Pharmacological inhibitors of the transforming growth factor β (TGFβ) type I receptor (ALK5) have shown promise in blocking growth of xenotransplanted cancer cell lines but the effect on a multistage cancer model is not known. To test this, we treated mouse skin with SB431542 (SB), a well-characterized ALK5 inhibitor, during a two-stage skin carcinogenesis assay. Topical SB significantly reduced the total number, incidence and size of papillomas compared with 12-O-tetradecanoylphorbol 13-acetate (TPA) promotion alone, and this was linked to increased epidermal apoptosis, decreased proliferation and decreased cutaneous inflammation during promotion. In contrast, the frequency of conversion to squamous cell carcinoma (SCC) was 2-fold higher in papillomas treated with SB. Although there was no difference in tumor cell proliferation in early premalignant lesions, those that formed after SB treatment exhibited reduced squamous differentiation and an altered inflammatory microenvironment similar to SCC. In an inducible epidermal RAS transgenic model, treatment with SB enhanced proliferation and cutaneous inflammation in skin but decreased expression of keratin 1 and increased expression of simple epithelial keratin 18, markers of premalignant progression. In agreement with increased frequency of progression in the multistage model, SB treatment resulted in increased tumor formation with a more malignant phenotype following long-term RAS induction. In contrast to the current paradigm for TGFβ in carcinogenesis, these results demonstrate that cutaneous TGFβ signaling enables promotion of benign tumors but suppresses premalignant progression through context-dependent regulation of epidermal homeostasis and inflammation.

Pathophysiology of oral cancer in experimental animal models: a review with focus on the role of sympathetic nerves

Global increase in incidence and mortality as well as poor prognosis of oral cancer (OC) has intensified efforts towards early detection and prevention of this disfiguring disease. Several studies have been conducted using experimental animal models to understand the pathophysiology and molecular events involved in OC. Lack of identification of specific biomarkers during the multifaceted steps of oral carcinogenesis has hindered its diagnosis and treatment. Solid stress generated by growing tumors as well as abnormalities in tumor vasculature lead to increased interstitial fluid pressure, which could obstruct therapeutic drug delivery to tumors. Furthermore, the sympathetic nervous system is known to affect angiogenesis, vessel permeability, immune responses and carcinogenesis. Recent findings indicate that, in addition to angiogenic and lymphangiogenic factors, tumor cells release neurotrophic factors that initiate innervation. Interactions between cytokines and sympathetic neurotransmitters, and their respective receptors expressed by the nerve, immune and tumor cells appear to influence tumor growth. Thus, understanding the complex signaling processes and interrelationships between vascular, nervous and immune systems during oral carcinogenesis may prove vital for successful prevention and treatment of OC. This review aims at outlining the available knowledge on pathophysiology of OC in experimental animal models including evidence from our own findings.

YAP dysregulation by phosphorylation or ΔNp63-mediated gene repression promotes proliferation, survival and migration in head and neck cancer subsets

Over-expression of Yes-associated protein (YAP), and TP53 family members ΔNp63 and p73 with which YAP may serve as a nuclear co-factor, have been independently detected in subsets of head and neck squamous cell carcinomas (HNSCC). Their potential relationship and functional role of YAP in HNSCC are unknown. Here we reveal that in a subset of HNSCC lines and tumors, YAP expression is increased but localized in the cytoplasm in association with increased AKT and YAP phosphorylation, and decreased expression of ΔNp63 and p73. Conversely, YAP expression is decreased but detectable in the nucleus in association with lower AKT and YAP phosphorylation, and increased ΔNp63 and p73 expression, in another subset. Inhibiting AKT decreased Serine-127 phosphorylation and enhanced nuclear translocation of YAP. ΔNp63 repressed YAP expression and bound its promoter. Transfection of a YAP-Serine-127-Alanine phosphoacceptor-site mutant or ΔNp63 knockdown significantly increased nuclear YAP and cell death. Conversely, YAP knockdown enhanced cell proliferation, survival, migration, and cisplatin chemoresistance. Thus, YAP function as a tumor suppressor may alternatively be dysregulated by AKT phosphorylation at Serine-127 and cytoplasmic sequestration, or by transcriptional repression by ΔNp63, in different subsets of HNSCC. AKT and/orΔNp63 are potential targets for enhancing YAP-mediated apoptosis and chemosensitivity in HNSCC.

TGFβ signaling in head and neck squamous cell carcinoma

Transforming growth factor beta (TGFβ) is a key regulator of epithelial cell proliferation, immune function and angiogenesis. Because TGFβ signaling maintains epithelial homeostasis, dysregulated TGFβ signaling is common in many malignancies, including head and neck squamous cell carcinoma (HNSCC). Defective TGFβ signaling in epithelial cells causes hyperproliferation, reduced apoptosis and increased genomic instability, and the compensatory increase in TGFβ production by tumor epithelial cells with TGFβ signaling defects further promotes tumor growth and metastases by increasing angiogenesis and inflammation in tumor stromal cells. Here, we review the mouse models that we used to study TGFβ signaling in HNSCC.

[Identifying candidate cancer genes based on co-evolving gene modules]

Data of somatic mutation screening of cancer genomes have provided us huge amounts of information for identifying new cancer genes. Current methods for identifying candidate cancer genes based on gene mutation frequencies tend to find cancer genes with high mutation frequencies. However, many genes with low mutation frequencies might also play important roles during tumorigenesis. Based on the assumption that genes with similar phylogenetic profiles and protein-protein interactions might have similar functions and their disruptions might lead to similar disease phenotypes, we proposed a new approach to find candidate cancer genes. First, we searched for protein-protein interaction subnetworks within which proteins have similar phylogenetic profiles, termed as co-evolving gene modules. Then, we identified genes that have at least one non-synonymous mutation in cancer genomes and directly interact with known cancer genes in the same co-evolving gene modules and predicted them as candidate cancer genes. In this way, we found 15 candidate cancer genes, among which only two genes had been identified previously as candidate cancer genes using the methods based on gene mutation frequencies. Thus, the candidate cancer genes with low mutation frequencies can be found by our method.

Smad4-mediated TGF-beta signaling in tumorigenesis

Transforming growth factor-β (TGF-β) family members exert their function via specific type I and type II serine/threonine kinase receptors and intracellular Smad transcription factors, including the common mediator Smad4. The dual effects of TGF-β signaling on tumor initiation and progression are cell-specific and yet to be determined under distinct contexts. A number of genetically manipulated mouse models with alterations in the TGF-β pathway genes, particularly the pivotal Smad4, revealed that these genes play crucial functions in maintaining tissue homeostasis and suppressing tumorigenesis. Loss of Smad4 plays a causal role in initiating squamous cell carcinomas of skin and upper digestive tract as well as adenocarcinomas of gastrointestinal tract. However, for some cancers like pancreatic and cholangiocellular carcinomas, Smad4 deficiency does not initiate the tumorigenesis but acts as a promoter to accelerate or synergize the development and progression of cancers that are started by other oncogenic pathways. Intriguingly, emerging evidences from mouse models have highlighted the important roles of non-cell autonomous effects of Smad4-mediated TGF-β signaling in the inhibition of oncogenesis. All these data have greatly deepened our understanding of molecular mechanisms of cell-autonomous and non-cell autonomous effect of Smad4-mediated TGF-β signaling in suppressing carcinogenesis, which may facilitate the development of successful therapies targeting TGF-β signaling for the treatment of human cancers.

Smad4-mediated TGF-beta signaling in tumorigenesis

Transforming growth factor-beta (TGF-beta) family members exert their function via specific type I and type II serine/threonine kinase receptors and intracellular Smad transcription factors, including the common mediator Smad4. The dual effects of TGF-beta signaling on tumor initiation and progression are cell-specific and yet to be determined under distinct contexts. A number of genetically manipulated mouse models with alterations in the TGF-beta pathway genes, particularly the pivotal Smad4, revealed that these genes play crucial functions in maintaining tissue homeostasis and suppressing tumorigenesis. Loss of Smad4 plays a causal role in initiating squamous cell carcinomas of skin and upper digestive tract as well as adenocarcinomas of gastrointestinal tract. However, for some cancers like pancreatic and cholangiocellular carcinomas, Smad4 deficiency does not initiate the tumorigenesis but acts as a promoter to accelerate or synergize the development and progression of cancers that are started by other oncogenic pathways. Intriguingly, emerging evidences from mouse models have highlighted the important roles of non-cell autonomous effects of Smad4-mediated TGF-beta signaling in the inhibition of oncogenesis. All these data have greatly deepened our understanding of molecular mechanisms of cell-autonomous and non-cell autonomous effect of Smad4-mediated TGF-beta signaling in suppressing carcinogenesis, which may facilitate the development of successful therapies targeting TGF-beta signaling for the treatment of human cancers.

Relationship between human oral lichen planus and oral squamous cell carcinoma at a genomic level: a datamining study

The leader gene approach is a data mining method based on the systematic search for genes involved in a specific process and their ranking according to the number of interconnections with the other genes identified. The genes with the strongest interconnections are termed leader genes, since they may be supposed to play an important role in the process. The potential of malignant progression of OLP to oral squamous cell carcinoma (OSCC) is still not completely clear. In this study, the leader gene approach is applied to investigate the association between OLP and OSCC at a molecular level. Results were integrated with those obtained in an experimental analysis (see paper 1 of this series). Genes involved in OLP and OSCC were identified by systematic queries to dedicated databases. Interconnections among identified genes were calculated and given a confidence value using STRING database. Leader genes were identified by clustering genes according to their interconnections. This theoretical analysis shows that OLP and OSCC share two leader genes: TP53 and CDKN1A, involved in the PI3K signalling events mediated by AKT pathway. This finding and those obtained in the experimental analysis suggest the possible involvement of some key genes/proteins LCK, PIK3CA, BIRC5, TP53 and CDKN1A in the malignant progression from OLP to OSCC. Moreover, these findings support the role of some molecular pathways, namely IL2 signalling events mediated by PI3K, PI3K signalling events mediated by AKT, and, possibly, Aurora A signalling in the association between OLP and OSCC.