Molecular introduction to head and neck cancer (HNSCC) carcinogenesis

https://doi.org/10.1016/j.bjps.2004.06.010Get rights and content

Abstract

Of all human cancers, HNSCC is the most distressing affecting pain, disfigurement, speech and the basic survival functions of breathing and swallowing. Mortality rates have not significantly changed in the last 40 years despite advances in radiotherapy and surgical treatment. Molecular markers are currently being identified that can determine prognosis preoperatively by routine tumour biopsy leading to improved management of HNSCC patients. The approach could help decide which early stage patient should have adjuvant neck dissection and radiotherapy, and whether later stage patients with operable lesions would benefit from resection and reconstructive surgery or adopt a conservative approach to patients with poor prognosis regardless of treatment. In the future, understanding these basic genetic changes in HNSCC would be important for the management of HNSCC.

Introduction

Oral cancer is one of the few cancer types where it is possible to obtain biopsies at all stages of the disease and study the genetic progression of tumorigenesis to metastasis. The pioneering work on the characterization of genetic alterations of colorectal cancer by Fearon and Vogelstein has become a paradigm for other human neoplasias (Diagram 1).1 It is now proposed that HNSCC follows a similar genetic progression in its development from premalignant lesions such as leukoplakia, dysplasia, erythroplakia and lichen planus. The precise nature of genetic alterations occurring at each step is still unclear but Califano et al. 1996 have described a preliminary HNSCC molecular progression model from benign to the invasive state with microsatellite analysis for allelic loss at 10 major chromosomal loci. The spectrum of chromosomal loss progressively increased at each histopathological step from benign hyperplasia to dysplasia to carcinoma in situ to invasive cancer (Diagram 2).2 Current established view on HNSCC formation requires the following three genetic alterations. The alterations are the p53 tumour suppressor protein, inactivation of the cyclin dependent kinase inhibitor p16 and overexpression of epidermal growth factor receptor (EGFR) in 40%,3 70%,4 and 90%5 of all oral cancers, respectively. With the advent of cDNA profiling of many thousands of genes in a single assay, a wide range of molecular markers are currently being identified that can distinguish patients' prognosis preoperatively. Traditionally, carcinogenesis and tumour progression has been attributed to alterations in oncogenes or tumour suppressor genes. This review will focus on the various established types of genetic alterations in HNSCC.

Section snippets

Hereditary

There is now increasing epidemiological evidence from case control studies of HNSCC patients that a family history of HNSCC is a risk factor. One matched case-control study using first-degree relatives of patients with new HNSCC, and first-degree relatives of the patients' spouses as controls, demonstrated an increased relative risk of 3.5 in association with a positive family history.6 Another large age and sex-matched study adjusting for alcohol consumption showed a similar relative risk of

The oncogenes

Oncogenes encode proteins that result in abnormal cell growth or tumorigenesis when overexpressed or mutated. The majority of these oncogenes are growth factors or growth factor receptors (hst-1, int-2, EGFR/erbB, c-erbB-2/Her-2, sis), intracellular signal transducers (ras, raf, stat-3), transcription factors (myc, fos, jun, c-myb), cell cycle regulators (Cyclin D1) and those involved in apoptosis (bcl-2, Bax). These growth regulatory pathways can be altered by gene mutation,8 chromosomal

Growth factor and receptors

EGFR (epidermal growth factor receptor) and its ligands have been studied extensively in HNSCC.12., 13., 14., 15. The m-RNA for EGFR was elevated in 69-fold in 92% of tumours when compared with normal mucosa.5 Overexpression of c-erbB-2 (Her-2), which is an EGFR like oncogene located on chromosome 17, has been observed in 75% of HNSCC patients and correlated to shorter survival.16

Chromosome 11q13 amplification

Fractional or entire DNA loss of chromosome 3p was found in 97% and amplifications of 11q13 region in 70% of primary HNSCC tumours.17 Amplification and rearrangements of the 11q13 region in primary HNSCC tumours has been reported in between 30–60% of cases using Southern hybridisation analysis.18., 19., 20. Amplification of the 11q13 region was correlated with high grade, late stage, aneuploid tumours,21., 22. poor prognosis,23 recurrence and distant metastasis.24

The oncogenes present in 11q13

The cell cycle regulator genes

Cylin D1 gene regulates initiation of DNA synthesis and G1/S transition of cells. It was initially identified as the bcl-1 gene at chromosome 11q13, at the site of translocation t(11:14) (q13:q32) in B-cell malignancies.27 Amplification of Cyclin D1 gene was reported in 34% of HNSCC.21., 24. The dysregulation of cyclin D1 expression has been shown to occur early during the tumorigenesis process in HNSCC and enables subsequent cyclin D1 gene amplification.28 The overall 5-year survival of HNSCC

Transcription factors

Saranath et al. in30 1989 studied 23 primary HNSCC and observed a 5- to 10-fold amplification of one or more of c-myc, N-myc, Ki-ras and N-ras oncogenes in 56% of the tumour tissue samples, with these oncogenes not being amplified in the peripheral blood cells of the same patients. L-myc and H-ras were not amplified in any of the samples. The oncogene amplifications seemed to be associated with advanced stages of squamous cell carcinomas, with the ras and myc family oncogenes being amplified in

Intracellular transducers

Up-regulation of EGFR occurs early in squamous cell carcinogenesis and is critical for the loss of growth control in a variety of human cancers, including HNSCC. The Jak/Stat signalling pathway transmits signals from many cytokines and growth factor receptors to target genes in the nucleus. In HNSCC cells culture, EGFR stimulation initiates signaling via persistent activation of selective STAT proteins. Grandis et al. 2000 were first to provide evidence that constitutively activated Stat-3 is

The Tumour suppressor genes and proteins

Tumour suppressor genes serve as transducers of negative growth signals.37 These genes are involved in cell cycle regulation including cell cycle arrest and apoptosis. Tumour suppressor genes can be altered in their functions by several mechanisms including point mutations, deletions or binding with cellular and viral proteins.37., 38.

Alterations in the p53 gene expression

The p53 gene is located on the short arm of chromosome 17p13.1 and encodes a 53 kDa nuclear phosphoprotein that maintains genome stability. It regulates cell cycle progression, cellular differentiation, DNA repair and apoptosis.39 Mutations of the p53 protein are the most frequent genetic alterations found in human malignancies.40

Usually, one of the p53 alleles is lost through a deletion, and the other is mutated. Thus, the tumour cells are, for all practical purposes, homozygous for the loss

Tumour suppressor gene p16 (CDKN2A, MTS1-multiple tumour suppressor 1)

The p16 protein is a tumour suppressor protein of 156 amino acids; 16.5 kDa in size and the gene, called CDKN2A (cyclin-dependent kinase inhibitor 2A) is located at 9p21.64 It interacts strongly with CDK4 and CDK6 and inhibits its ability to interact with Cyclin D and function as a negative regulator of proliferation of normal cells.65 This effect is mediated through the retinoblastoma protein (Rb), another tumour suppressor.

The Rb protein is found in the nucleus of cells. When active

Regulation of apoptosis

Bax, Bcl-2, and p53 proteins are involved in the regulation of apoptosis and have been reported to correlate with prognosis in several tumour types. Over-expression of Bcl-2 and loss of Bax expression is significantly associated with poor prognosis. High apoptosis was significantly associated with high Bax expression and highly differentiated tumours.71

Other tumour suppressor genes associated with HNSCC

The p15 gene has been designated MTS2 ‘multiple tumour suppressor 2’ (CDKN2B). It is deleted in 10–50% of HNSCC.72 It is thought that loss of 9p is an early event in the development of HNSCC.2 Loss of heterozygosity (LOH) at 9p21-22 was reported in 72% of 29 HNSCC cases studied.73

The p21 gene is mapped to chromosome 6p21. The p21 tumour suppressor protein was found to inactivate cyclin E-cdk-2 and cyclin D1, D2, D3- cdk-4 complexes components of the regulatory kinases that target pRB for

Angiogenesis

Tumour growth is associated with elevated cellular activities and increased blood supply is crucial for its continuing development. The process of angiogenesis is in itself a multi-step process that appears to be regulated by both stimulatory and inhibitory factors.77 Steps critical to successful neovascularization include degradation of the extracellular matrix, endothelial cell proliferation, migration and remodelling of extracellular matrix.

Angiogenesis has been linked to increased

Acknowledgements

The authors would like to acknowledge and thank the following funding bodies: Queensland Cancer Fund Clinical Fellowship Garnett-Passe and Rodney Williams Memorial Foundation Project Grant University of Queensland Graduate School Scholarship.

References (85)

  • T. Veikkola et al.

    VEGFs, receptors and angiogenesis

    Semin Cancer Biol

    (1999)
  • J. Califano et al.

    Genetic progression model for head and neck cancer: implications for field cancerization

    Cancer Res

    (1996)
  • M. Sartor et al.

    Role of p16/MTS1, cyclin D1 and RB in primary oral cancer and oral cancer cell lines

    Br J Cancer

    (1999)
  • J.R. Grandis et al.

    Elevated levels of transforming growth factor alpha and epidermal growth factor receptor messenger RNA are early markers of carcinogenesis in head and neck cancer

    Cancer Res

    (1993)
  • M.P. Copper et al.

    Role of genetic factors in the etiology of squamous cell carcinoma of the head and neck

    Arch Otolaryngol Head Neck Surg

    (1995)
  • W.D. Foulkes et al.

    Family history of cancer is a risk factor for squamous cell carcinoma of the head and neck in Brazil: a case-control study

    Int J Cancer

    (1995)
  • G. Klein et al.

    Evolution of tumours and the impact of molecular oncology

    Nature

    (1985)
  • F.G. Haluska et al.

    Oncogene activation by chromosome translocation in human malignancy

    Annu Rev Genet

    (1987)
  • Bishop

    Cellular oncogenes and retroviruses

    Ann Rev Biochem

    (1983)
  • J.R. Grandis et al.

    Levels of TGF-alpha and EGFR protein in head and neck squamous cell carcinoma and patient survival

    J Natl Cancer Inst

    (1998)
  • Y. He et al.

    Inhibition of human squamous cell carcinoma growth in vivo by epidermal growth factor receptor antisense RNA transcribed from the U6 promoter

    J Natl Cancer Inst

    (1998)
  • D.C. Nguyen et al.

    Overexpression of cell cycle regulatory proteins correlates with advanced tumor stage in head and neck squamous cell carcinomas

    Int J Oncol

    (2003)
  • W. Xia et al.

    Strong correlation between c-erbB-2 overexpression and overall survival of patients with oral squamous cell carcinoma

    Clin Cancer Res

    (1997)
  • U. Bockmuhl et al.

    Distinct patterns of chromosomal alterations in high- and low-grade head and neck squamous cell carcinomas

    Cancer Res

    (1996)
  • S.D. Meredith et al.

    Chromosome 11q13 amplification in head and neck squamous cell carcinoma. Association with poor prognosis

    Arch Otolaryngol Head Neck Surg

    (1995)
  • J.A. Akervall et al.

    Chromosomal abnormalities involving 11q13 are associated with poor prognosis in patients with squamous cell carcinoma of the head and neck

    Cancer

    (1995)
  • J.S. Rubin et al.

    Amplification of the Int-2 gene in head and neck squamous cell carcinoma

    J Laryngol Otol

    (1995)
  • T. Callender et al.

    PRAD-1 (CCND1)/cyclin D1 oncogene amplification in primary head and neck squamous cell carcinoma

    Cancer

    (1994)
  • M.E. Williams et al.

    Chromosome 11Q13 amplification in head and neck squamous cell carcinoma

    Arch Otolaryngol Head Neck Surg

    (1993)
  • U. Bockmuhl et al.

    Improved prognostic assessment of head-neck carcinomas by new genetic markers

    Hno

    (2000)
  • A. Namazie et al.

    Cyclin D1 amplification and p16(MTS1/CDK4I) deletion correlate with poor prognosis in head and neck tumors

    Laryngoscope

    (2002)
  • K.D. Somers et al.

    Amplification of the int-2 gene in human head and neck squamous cell carcinomas

    Oncogene

    (1990)
  • W.D. Merritt et al.

    Oncogene amplification in squamous cell carcinoma of the head and neck

    Arch Otolaryngol Head Neck Surg

    (1990)
  • J.J. Yunis

    The chromosomal basis of human neoplasia

    Science

    (1983)
  • J.G. Izzo et al.

    Dysregulated cyclin D1 expression early in head and neck tumorigenesis: in vivo evidence for an association with subsequent gene amplification

    Oncogene

    (1998)
  • R. Kyomoto et al.

    Cyclin-D1-gene amplification is a more potent prognostic factor than its protein over-expression in human head-and-neck squamous-cell carcinoma

    Int J Cancer

    (1997)
  • D. Saranath et al.

    Oncogene amplification in squamous cell carcinoma of the oral cavity

    Jpn J Cancer Res

    (1989)
  • M.J. Frederick et al.

    Expression of apoptosis-related genes in human head and neck squamous cell carcinomas undergoing p53-mediated programmed cell death

    Clin Cancer Res

    (1999)
  • J. Xu et al.

    Alterations of p53, cyclin D1, Rb, and H-ras in human oral carcinomas related to tobacco use

    Cancer

    (1998)
  • D. Saranath et al.

    High frequency mutation in codons 12 and 61 of H-ras oncogene in chewing tobacco-related human oral carcinoma in India

    Br J Cancer

    (1991)
  • J.R. Grandis et al.

    Epidermal growth factor receptor–mediated stat3 signaling blocks apoptosis in head and neck cancer

    Laryngoscope

    (2000)
  • J.R. Grandis et al.

    Constitutive activation of Stat3 signaling abrogates apoptosis in squamous cell carcinogenesis in vivo

    Proc Natl Acad Sci USA

    (2000)
  • Cited by (0)

    View full text