Distinct roles of PIK3CA in the enrichment and maintenance of cancer stem cells in head and neck squamous cell carcinoma.

Recurrence and metastasis are the major causes of mortality in head and neck squamous cell carcinoma (HNSCC). It is suggested that cancer stem cells (CSCs) play pivotal roles in recurrence and metastasis. Thus, a greater understanding of the mechanisms of CSC regulation may provide opportunities to develop novel therapies for improving survival by controlling recurrence or metastasis. Here, we report that overexpression of the gene encoding the catalytic subunit of PI3K (PIK3CA), the most frequently amplified oncogene in HNSCC, promotes epithelial-to-mesenchymal transition and enriches the CSC population. However, PIK3CA is not required to maintain these traits and inhibition of the phosphatidylinositol 3-kinase (PI3K) signaling pathway paradoxically promotes CSC population. Molecular analysis revealed that overexpression of PIK3CA activates multiple receptor tyrosine kinases (RTKs), in which ephrin receptors (Ephs), tropomyosin receptor kinases (TRK) and mast/stem cell growth factor receptor (c-Kit) contribute to maintain CSC population. Accordingly, simultaneous inhibition of these RTKs using a multi-kinase inhibitor ponatinib has a superior effect at eliminating the CSC population and reduces metastasis of PIK3CA-overexpressing HNSCC cells. Our result suggests that co-targeting of Ephs, TRKs and the c-Kit pathway may be effective at eliminating the PI3K-independent CSC population, thereby providing potential targets for future development of a novel anti-CSC therapeutic approach for HNSCC patients, particularly for patients with PIK3CA amplification.

Methylated genomic loci encoding microRNA as a biomarker panel in tissue and saliva for head and neck squamous cell carcinoma.

Background: To identify aberrant promoter methylation of genomic loci encoding microRNA (mgmiR) in head and neck squamous cell carcinoma (HNSCC) and to evaluate a biomarker panel of mgmiRs to improve the diagnostic accuracy of HNSCC in tissues and saliva. Methods: Methylation of promoter regions of mgmiR candidates was initially screened using HNSCC and control cell lines and further selected using HNSCC and control tissues by quantitative methylation-specific PCR (qMS-PCR). We then examined a panel of seven mgmiRs for validation in an expanded cohort including 189 HNSCC and 92 non-HNSCC controls. Saliva from 86 pre-treatment HNSCC patients and 108 non-HNSCC controls was also examined using this panel of seven mgmiRs to assess the potentials of clinical utilization. Results: Among the 315 screened mgmiRs, 12 mgmiRs were significantly increased in HNSCC cell lines compared to control cell lines. Seven out of the 12 mgmiRs, i.e., mgmiR9-1, mgmiR124-1, mgmiR124-2, mgmiR124-3, mgmiR129-2, mgmiR137, and mgmiR148a, were further found to significantly increase in HNSCC tumor tissues compared to control tissues. Using multivariable logistic regression with dichotomized variables, a combination of the seven mgmiRs had sensitivity and specificity of 92.6 and 92.4% in tissues and 76.7 and 86.1% in saliva, respectively. Area under the receiver operating curve for this panel was 0.97 in tissue and 0.93 in saliva. This model was validated by independent bootstrap validation and random forest analysis. Conclusions: mgmiR biomarkers represent a novel and promising screening tool, and the seven-mgmiR panel is able to robustly detect HNSCC in both patient tissue and saliva.

Immune recognition of irradiated cancer cells.

Ionizing irradiation has been extensively employed for the clinical management of solid tumors, with therapeutic or palliative intents, for decades. Until recently, radiation therapy (RT) was believed to mediate antineoplastic activity mostly (if not only) as a consequence of cancer cell-intrinsic effects. Indeed, the macromolecular damage imposed to malignant cells by RT initiates one or multiple signal transduction cascades that drive a permanent proliferative arrest (cellular senescence) or regulated cell death. Both these phenomena show a rather linear dose-response correlation. However, RT also mediates consistent immunological activity, not only as an "on-target effect" originating within irradiated cancer cells, but also as an "off-target effect" depending on the interaction between RT and stromal, endothelial, and immune components of the tumor microenvironment. Interestingly, the immunological activity of RT does not exhibit linear dose-response correlation. Here, we discuss the mechanisms whereby RT alters the capacity of the immune system to recognize and eliminate irradiated cancer cells, either as an "on-target" or as on "off-target" effect. In particular, we discuss the antagonism between the immunostimulatory and immunosuppressive effects of RT as we delineate combinatorial strategies to boost the former at the expenses of the latter.

IL-10 and integrin signaling pathways are associated with head and neck cancer progression.

BACKGROUND: Head and neck cancer is morbid with a poor prognosis that has not significantly improved in the past several decades. The purpose of this study was to identify biological pathways underlying progressive head and neck cancer to inform prognostic and adjuvant strategies. We identified 235 head and neck cancer patients in The Cancer Genome Atlas (TCGA) with sufficient clinical annotation regarding therapeutic treatment and disease progression to identify progressors and non-progressors. We compared primary tumor gene expression and mutational status between these two groups. RESULTS: 105 genes were differentially expressed between progressors and nonprogressors (FDR < 0.05). Pathway analyses revealed deregulation (FDR < 0.05) of multiple pathways related to integrin signaling as well as IL-10 signaling. A number of genes were uniquely mutated in the progressor cohort including increased frequency of truncating mutations in CTCF (P = 0.007). An 11-gene signature derived from a combination of unique mutations and differential expression was identified (PAGE4, SMTNL1, VTN, CA5A, C1orf43, KRTAP19-1, LEP, HRH4, PAGE5, SEZ6L, CREB3). This signature was associated with decreased overall survival (Logrank Test; P = 0.03443). Cox modeling of both key clinical features and the signature was significant (P = 0.032) with the greatest prognostic improvement seen in the model based on nodal extracapsular spread and alcohol use alone (P = 0.004). CONCLUSIONS: Molecular analyses of head and neck cancer tumors that progressed despite treatment, identified IL-10 and integrin pathways to be strongly associated with cancer progression. In addition, we identified an 11-gene signature with implications for patient prognostication. Mutational analysis highlighted a potential role for CTCF, a crucial regulator of long-range chromatin interactions, in head and neck cancer progression.

Effect of ionizing radiation on the physical biology of head and neck squamous cell carcinoma cells.

Head and neck squamous cell carcinoma (HNSCC) is the sixth leading cause of cancer worldwide. Although there are numerous treatment options for HNSCC, such as surgery, cytotoxic chemotherapy, molecularly targeted systemic therapeutics, and radiotherapy, overall survival has not significantly improved in the last 50 years. This suggests a need for a better understanding of how these cancer cells respond to current treatments in order to improve treatment paradigms. Ionizing radiation (IR) promotes cancer cell death through the creation of cytotoxic DNA lesions, including single strand breaks, base damage, crosslinks, and double strand breaks (DSBs). As unrepaired DSBs are the most cytotoxic DNA lesion, defining the downstream cellular responses to DSBs are critical for understanding the mechanisms of tumor cell responses to IR. The effects of experimental IR on HNSCC cells beyond DNA damage in vitro are ill-defined. Here we combined label-free, quantitative phase and fluorescent microscopy to define the effects of IR on the dry mass and volume of the HNSCC cell line, UM-SCC-22A. We quantified nuclear and cytoplasmic subcellular density alterations resulting from 8 Gy X-ray IR and correlated these signatures with DNA and γ-H2AX expression patterns. This study utilizes a synergistic imaging approach to study both biophysical and biochemical alterations in cells following radiation damage and will aid in future understanding of cellular responses to radiation therapy.

B cells regulate macrophage phenotype and response to chemotherapy in squamous carcinomas.

B cells foster squamous cell carcinoma (SCC) development through deposition of immunoglobulin-containing immune complexes in premalignant tissue and Fcγ receptor-dependent activation of myeloid cells. Because human SCCs of the vulva and head and neck exhibited hallmarks of B cell infiltration, we examined B cell-deficient mice and found reduced support for SCC growth. Although ineffective as a single agent, treatment of mice bearing preexisting SCCs with B cell-depleting αCD20 monoclonal antibodies improved response to platinum- and Taxol-based chemotherapy. Improved chemoresponsiveness was dependent on altered chemokine expression by macrophages that promoted tumor infiltration of activated CD8(+) lymphocytes via CCR5-dependent mechanisms. These data reveal that B cells, and the downstream myeloid-based pathways they regulate, represent tractable targets for anticancer therapy in select tumors.

Epithelial stem cell mutations that promote squamous cell carcinoma metastasis.

Squamous cell carcinomas (SCCs) originate in stratified epithelia, with a small subset becoming metastatic. Epithelial stem cells are targets for driver mutations that give rise to SCCs, but it is unknown whether they contribute to oncogenic multipotency and metastasis. We developed a mouse model of SCC by targeting two frequent genetic mutations in human SCCs, oncogene Kras(G12D) activation and Smad4 deletion, to mouse keratin 15-expressing (K15+) stem cells. We show that transgenic mice developed multilineage tumors, including metastatic SCCs. Among cancer stem cell-enriched (CSC-enriched) populations, those with increased side population (SP) cells correlated with epithelial-mesenchymal transition (EMT) and lung metastasis. We show that microRNA-9 (miR-9) contributed to SP expansion and metastasis, and miR-9 inhibition reduced the number of SP cells and metastasis. Increased miR-9 was detected in metastatic human primary SCCs and SCC metastases, and miR-9-transduced human SCC cells exhibited increased invasion. We identified α-catenin as a predominant miR-9 target. Increased miR-9 in human SCC metastases correlated with α-catenin loss but not E-cadherin loss. Our results demonstrate that stem cells with Kras(G12D) activation and Smad4 depletion can produce tumors that are multipotent and susceptible to EMT and metastasis. Additionally, tumor initiation and metastatic properties of CSCs can be uncoupled, with miR-9 regulating the expansion of metastatic CSCs.

Surveillance low-dose chest computed tomography for head and neck cancer patients.

Based on the recent results of the National Lung Cancer Screening Trial, the National Comprehensive Cancer Network now recommends annual screening with low-dose computed tomography for high-risk individuals (generally defined as 45- to 60-year-old current or former smokers). As head and neck cancer patients are at a high risk for (second) lung cancers, annual surveillance computed tomography should be considered for head and neck cancer patients.

Tobacco-specific carcinogen nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone induces AKT activation in head and neck epithelia.

Exposure to tobacco carcinogens is causally associated with head and neck squamous cell carcinoma (HNSCC), but the underlying molecular mechanisms remain unclear. Here, we reported that AKT is activated at a higher frequency in both HNSCC tumors and the adjacent mucosa from HNSCC patients who are smokers than those from HNSCC patients who are non-smokers. Adding physiologically relevant concentrations of 4-(methylnitrosamino)-1-(3-pyridyl)-1-1butanone (NNK), a major tobacco carcinogen, to normal head and neck epithelial cells and HNSCC cell lines, rapidly and constitutively activated AKT through phosphorylation in a dose- and time-dependent manner. AKT phosphorylation was associated with activation of downstream signaling mediators BAD, MDM2, GSK-3ß, mTOR. These alterations correlated with increased proliferation and decreased etoposide-induced apoptosis in NNK-exposed cells. Finally, NNK exposure to mouse head and neck epithelia resulted in epithelial hyperproliferation and reduced apoptosis, which is correlated with AKT activation. Our results suggest that AKT activation is an early event and plays a pivotal role in mediating tobacco-induced HNSCC carcinogenesis.

Smad4 loss in mice causes spontaneous head and neck cancer with increased genomic instability and inflammation.

Smad4 is a central mediator of TGF-beta signaling, and its expression is downregulated or lost at the malignant stage in several cancer types. In this study, we found that Smad4 was frequently downregulated not only in human head and neck squamous cell carcinoma (HNSCC) malignant lesions, but also in grossly normal adjacent buccal mucosa. To gain insight into the importance of this observation, we generated mice in which Smad4 was deleted in head and neck epithelia (referred to herein as HN-Smad4-/- mice) and found that they developed spontaneous HNSCC. Interestingly, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited increased genomic instability, which correlated with downregulated expression and function of genes encoding proteins in the Fanconi anemia/Brca (Fanc/Brca) DNA repair pathway linked to HNSCC susceptibility in humans. Consistent with this, further analysis revealed a correlation between downregulation of Smad4 protein and downregulation of the Brca1 and Rad51 proteins in human HNSCC. In addition to the above changes in tumor epithelia, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited severe inflammation, which was associated with increased expression of TGF-beta1 and activated Smad3. We present what we believe to be the first single gene-knockout model for HNSCC, in which both HNSCC formation and invasion occurred as a result of Smad4 deletion. Our results reveal an intriguing connection between Smad4 and the Fanc/Brca pathway and highlight the impact of epithelial Smad4 loss on inflammation.

Distinct roles of individual Smads in skin carcinogenesis.

Transforming growth factor beta (TGFbeta) signaling has both tumor suppression and promotion roles. Smads are transcription factors that primarily mediate intracellular signaling for the TGFbeta superfamily. Loss of Smad2 and Smad4, but not Smad3 is common in human cancers. Given the complex nature of TGFbeta signaling, dissection of the distinct role of each Smad in mediating the multiple functions of TGFbeta signaling is warranted. To further analyze Smad deregulation during carcinogenesis, Smad2, Smad3, Smad4, and Smad7 were genetically modified in murine epidermis, and each alteration resulted in distinct skin phenotypes. Based on data from human cancer samples and from experimental models, Smad2 and Smad4 mainly function as tumor suppressors in skin carcinogenesis in vivo, whereas Smad3 and Smad7 may have dual roles in cancer. This review intends to summarize recent advances in the elucidation of the roles of Smad2, Smad3, Smad4, and Smad7 in skin carcinogenesis.

Loss of transforming growth factor-beta type II receptor promotes metastatic head-and-neck squamous cell carcinoma.

The prognosis of head-and-neck squamous cell carcinoma (HNSCC) has not been improved in the past 20 years. Validation of HNSCC biomarkers for targeted therapy has been hindered by a lack of animal models mimicking human HNSCC at both the pathological and molecular levels. Here we report that overexpression of K-ras or H-ras and loss of transforming growth factor-beta type II receptor (TGFbetaRII) are common events in human HNSCC. Activation of either K-ras or H-ras in combination with TGFbetaRII deletion from mouse head-and-neck epithelia caused HNSCC with complete penetrance, some of which progressed to metastases. These tumors displayed pathology indistinguishable from human HNSCCs and exhibited multiple molecular alterations commonly found in human HNSCCs. Additionally, elevated endogenous TGFbeta1 in these lesions contributed to inflammation and angiogenesis. Our data suggest that targeting common oncogenic pathways in tumor epithelia together with blocking the effect of TGFbeta1 on tumor stroma may provide a novel therapeutic strategy for HNSCC.

Copy number aberrations in mouse breast tumors reveal loci and genes important in tumorigenic receptor tyrosine kinase signaling.

Receptor tyrosine kinase (RTK) signaling plays a key role in the development of breast cancer. Defining the genes and pathways in the RTK signaling network that are important regulators of tumorigenesis in vivo will unveil potential candidates for targeted therapeutics. To this end, we used microarray comparative genomic hybridization to identify and compare copy number aberrations in five mouse models of breast cancer induced by wild-type and mutated forms of oncogenic ErbB2 or the polyomavirus middle T antigen (PyMT). We observed distinct genomic alterations among the various models, including recurrent chromosome 11 amplifications and chromosome 4 deletions, syntenic with human 17q21-25 and 1p35-36, respectively. Expression of oncogenic Erbb2 (NeuNT) under control of the endogenous Erbb2 promoter results in frequent (85%) amplification at the Erbb2 locus with striking structural similarity to the human amplicon, resulting in overexpression of at least two of the genes, Erbb2 and Grb7. Chromosome 11 amplicons distal to Erbb2 arise in a model (DB) overexpressing a mutant variant of PyMT (Y315/322F) unable to activate phosphatidylinositol 3-kinase. These amplicons are not observed in DB hyperplasias or in tumors overexpressing wild-type PyMT and result in overexpression of Grb2 and Itgb4. Distal chromosome 4 deletions occur in a significantly higher proportion of Erbb2 than PyMT tumors and encompass 14-3-3sigma (Stratifin), which is expressed at low or undetectable levels in the majority of NeuNT tumors. Our studies highlight loci and genes important in the regulation of tumorigenic RTK signaling in mammary epithelial cells in vivo.