Susanne M. Gollin

The Epidemiology and Risk Factors of Head and Neck Cancer: a Focus on Human Papillomavirus

Head and neck cancer was the eighth leading cause of cancer death worldwide in 2000. Although the incidence of head and neck squamous cell carcinoma (HNSCC) in the United States is relatively low, survival is poor and has not improved for several decades. While tobacco and alcohol are the primary risk factors for HNSCC development, epidemiological studies report a strong association with human papillomavirus (HPV) in a subset of HNSCC. More than 95% of cervical squamous cell carcinomas are linked to persistent HPV infection; evidence demonstrates that HPV is a necessary carcinogen. Not all HPV-positive HNSCC express the viral oncogenes (E6 and E7), which suggests that HPV may function as a carcinogen in a smaller proportion of HNSCC. This review presents our current understanding of the relationship between HPV and HNSCC, and describes future research directions that may lead to a better understanding of the involvement of HPV in head and neck cancer.

Chromosomal alterations in squamous cell carcinomas of the head and neck : Window to the biology of disease

Cytogenetic alterations underlie the development of squamous cell carcinomas of the head and neck (SCCHN). Because many of the molecular genetic changes in SCCHN result from chromosomal alterations, a complete perspective on the genetic changes in tumors requires a basic introduction to cytogenetics. This review presents a brief description of the latest cytogenetic techniques and a description of chromosomal alterations in SCCHN, their molecular correlates, and clinical implications.

Somatic mutation and gain of copy number of PIK3CA in human breast cancer.

IntroductionPhosphatidylinositol 3-kinases (PI3Ks) are a group of lipid kinases that regulate signaling pathways involved in cell proliferation, adhesion, survival, and motility. Even though PIK3CA amplification and somatic mutation have been reported previously in various kinds of human cancers, the genetic change in PIK3CA in human breast cancer has not been clearly identified.MethodsFifteen breast cancer cell lines and 92 primary breast tumors (33 with matched normal tissue) were used to check somatic mutation and gene copy number of PIK3CA. For the somatic mutation study, we specifically checked exons 1, 9, and 20, which have been reported to be hot spots in colon cancer. For the analysis of the gene copy number, we used quantitative real-time PCR and fluorescence in situ hybridization. We also treated several breast cancer cells with the PIK3CA inhibitor LY294002 and compared the apoptosis status in cells with and without PIK3CA mutation.ResultsWe identified a 20.6% (19 of 92) and 33.3% (5 of 15) PIK3CA somatic mutation frequency in primary breast tumors and cell lines, respectively. We also found that 8.7% (8 of 92) of the tumors harbored a gain of PIK3CA gene copy number. Only four cases in this study contained both an increase in the gene copy number and a somatic mutation. In addition, mutation of PIK3CA correlated with the status of Akt phosphorylation in some breast cancer cells and inhibition of PIK3CA-induced increased apoptosis in breast cancer cells with PIK3CA mutation.ConclusionSomatic mutation rather than a gain of gene copy number of PIK3CA is the frequent genetic alteration that contributes to human breast cancer progression. The frequent and clustered mutations within PIK3CA make it an attractive molecular marker for early detection and a promising therapeutic target in breast cancer.

Resolution of anaphase bridges in cancer cells

Chromosomal instability is a key step in the generation of the cancer cell karyotype. An indicator of unstable chromosomes is the presence of chromatin bridges during anaphase. We examined in detail the fate of anaphase bridges in cultured oral squamous cell carcinoma cells in real-time. Surprisingly, chromosomes in bridges typically resolve by breaking into multiple fragments. Often these fragments give rise to micronuclei (MN) at the end of mitosis. The formation of MN is shown to have important consequences for the cell. We found that MN have incomplete nuclear pore complex (NPC) formation and nuclear import defects and the chromatin within has greatly reduced transcriptional activity. Thus, a major consequence of the presence of anaphase bridges is the regular sequestration of chromatin into genetically inert MN. This represents another source of ongoing genetic instability in cancer cells.

Decreased expression of miR-125b and miR-100 in oral cancer cells contributes to malignancy.

Altered microRNA (miRNA) expression profiles have been observed in numerous malignancies, including oral squamous cell carcinoma (OSCC). However, their role in disease is not entirely clear. Several genetic aberrations are characteristic of OSCC, with amplification of chromosomal band 11q13 and loss of distal 11q being among the most prevalent. It is not known if the expression levels of miRNAs in these regions are altered or whether they play a role in disease. We hypothesize that the expression of miRNAs mapping to 11q are altered in OSCC because of loss or amplification of chromosomal material, and that this contributes to the development and progression of OSCC. We found that miR‐125b and miR‐100 are down‐regulated in OSCC tumor and cell lines, and that transfecting cells with exogenous miR‐125b and miR‐100 significantly reduced cell proliferation and modified the expression of target and nontarget genes, including some that are overexpressed in radioresistant OSCC cells. In conclusion, the down‐regulation of miR‐125b and miR‐100 in OSCC appears to play an important role in the development and/or progression of disease and may contribute to the loss of sensitivity to ionizing radiation.

High-resolution mapping of the 11q13 amplicon and identification of a gene, TAOS1, that is amplified and overexpressed in oral cancer cells

Amplification of chromosomal band 11q13 is a common event in human cancer. It has been reported in about 45% of head and neck carcinomas and in other cancers including esophageal, breast, liver, lung, and bladder cancer. To understand the mechanism of 11q13 amplification and to identify the potential oncogene(s) driving it, we have fine-mapped the structure of the amplicon in oral squamous cell carcinoma cell lines and localized the proximal and distal breakpoints. A 5-Mb physical map of the region has been prepared from which sequence is available. We quantified copy number of sequence-tagged site markers at 42–550 kb intervals along the length of the amplicon and defined the amplicon core and breakpoints by using TaqMan-based quantitative microsatellite analysis. The core of the amplicon maps to a 1.5-Mb region. The proximal breakpoint localizes to two intervals between sequence-tagged site markers, 550 kb and 160 kb in size, and the distal breakpoint maps to a 250 kb interval. The cyclin D1 gene maps to the amplicon core, as do two new expressed sequence tag clusters. We have analyzed one of these expressed sequence tag clusters and now report that it contains a previously uncharacterized gene, TAOS1 (tumor amplified and overexpressed sequence 1), which is both amplified and overexpressed in oral cancer cells. The data suggest that TAOS1 may be an amplification-dependent candidate oncogene with a role in the development and/or progression of human tumors, including oral squamous cell carcinomas. The approach described here should be useful for characterizing amplified genomic regions in a wide variety of tumors.

Head and neck squamous cell carcinoma cell lines: established models and rationale for selection.

Head and neck squamous cell carcinoma (HNSCC) cell lines are important preclinical models in the search for novel and targeted therapies to treat head and neck cancer. Unlike many other cancer types, a wide variety of primary and metastatic HNSCC cell lines are available. An easily accessible guide that organizes important characteristics of HNSCC cell lines would be valuable for the selection of appropriate HNSCC cell lines for in vitro or in vivo studies.

TMEM16A, induces MAPK and contributes directly to tumorigenesis and cancer progression

Frequent gene amplification of the receptor-activated calcium-dependent chloride channel TMEM16A (TAOS2 or ANO1) has been reported in several malignancies. However, its involvement in human tumorigenesis has not been previously studied. Here, we show a functional role for TMEM16A in tumor growth. We found TMEM16A overexpression in 80% of head and neck squamous cell carcinoma (SCCHN), which correlated with decreased overall survival in patients with SCCHN. TMEM16A overexpression significantly promoted anchorage-independent growth in vitro, and loss of TMEM16A resulted in inhibition of tumor growth both in vitro and in vivo. Mechanistically, TMEM16A-induced cancer cell proliferation and tumor growth were accompanied by an increase in extracellular signal-regulated kinase (ERK)1/2 activation and cyclin D1 induction. Pharmacologic inhibition of MEK/ERK and genetic inactivation of ERK1/2 (using siRNA and dominant-negative constructs) abrogated the growth effect of TMEM16A, indicating a role for mitogen-activated protein kinase (MAPK) activation in TMEM16A-mediated proliferation. In addition, a developmental small-molecule inhibitor of TMEM16A, T16A-inh01 (A01), abrogated tumor cell proliferation in vitro. Together, our findings provide a mechanistic analysis of the tumorigenic properties of TMEM16A, which represents a potentially novel therapeutic target. The development of small-molecule inhibitors against TMEM16A may be clinically relevant for treatment of human cancers, including SCCHN.

A Stochastic Model for Cancer Stem Cell Origin in Metastatic Colon Cancer

Human cancers have been found to include transformed stem cells that may drive cancer progression to metastasis. Here, we report that metastatic colon cancer contains clonally derived tumor cells with all of the critical properties expected of stem cells, including self-renewal and the ability to differentiate into mature colon cells. Additionally, when injected into mice, these cells initiated tumors that closely resemble human cancer. Karyotype analyses of parental and clonally derived tumor cells expressed many consistent (clonal) along with unique chromosomal aberrations, suggesting the presence of chromosomal instability in the cancer stem cells. Thus, this new model for cancer origin and metastatic progression includes features of both the hierarchical model for cancerous stem cells and the stochastic model, driven by the observation of chromosomal instability.

Comprehensive genome and transcriptome analysis of the 11q13 amplicon in human oral cancer and synteny to the 7F5 amplicon in murine oral carcinoma

11q13 amplification occurs in a wide variety of tumors, including almost half of oral squamous cell carcinomas (OSCC) where it has been correlated with a poor outcome. In this study, we compiled 3.6 Mb of DNA sequence in the 11q13 amplicon core and refined the physical map of the amplicon. In the process, we determined the genomic structure and normal tissue expression patterns of two recently identified genes, TAOS2/TMEM16A and MRGF, which reside in the amplicon core. We then quantified DNA copy number and mRNA expression of all genes in the 11q13 amplicon in cell lines and primary tumors from OSCC. With the exception of FGF3, FGF4, FGF19, and MRGF, all genes were overexpressed in most tumors with genomic amplification. Furthermore, we found that the expression of genes in the amplicon appeared to be highly coordinated, making it difficult to determine which gene or genes are driving amplification. However, in nonamplified primary tumors, three genes, TAOS2/TMEM16A, OCIM, and TPCN2, are frequently overexpressed, whereas CCND1 and EMS1 are not. These results suggest that in addition to CCND1 and EMS1, other important genes also may be target genes driving 11q13 amplification. We hypothesize that 11q13 amplification may be driven by a cassette of genes that provide growth or metastatic advantage to cancer cells. This is supported by the finding that the human 11q13 amplicon core is syntenic to mouse chromosomal band 7F5, which is frequently amplified in chemically induced murine OSCC. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045‐2257/suppmat.