Can you begin by outlining the focus of your research?

Over the last 15 years our research has focused on the causes of epithelial cancer and the development of novel gene-based risk assessment methods. In short, our efforts concentrate on two fundamental pathways: signal transduction and DNA repair. Over the years we have conducted various population studies in Europe, the U.S. and Asia where we have collected data and biological specimens from thousands of volunteers. Miraculously, we have witnessed a convergence of the data into certain domains of aetiology.

Tumours of the upper aerodigestive tract include lung cancer, cancers of the oral cavity, pharynx, larynx, and the esophagus. What are the main obstacles in controlling these cancers in patients?

One of the major challenges in controlling upper aerodigestive tract cancers (UACs) is the fact that most lesions are detected late – that is, after the tumour has spread to distant locations such as the brain. Even for anatomic locations that are easily accessible to direct visual and tactile examination – such as the oral cavity – experience shows that the majority of patients are diagnosed with some form of localised or distant metastasis.

Metastasis affects both the treatment choices that physicians have, and the patient’s prognosis. Aside from mortality, intense multi-modality treatments usually cause more side effects, subsequently leading to signifi cant reductions in the patient’s quality of life and his/her survival potential.

In developing your risk assessment methods, what metrics have been devised in gauging the probability of an individual contracting UAC?

Risk assessment requires data on traditional risk factors associated with human behaviour, such as the frequency and type of tobacco or alcohol use, details on diet and demographics, and information about exposure to environmental contaminants such as asbestos. Tobacco in particular is a major aetiologic factor. However, not all smokers develop cancer and not all cancers occur in smokers. Research shows that lack of absolute predictability makes humans take chances, discounting even solid epidemiologic evidence. Thus, better methods are needed to explain the complexity and variability of the carcinogenic process. For example, assays measuring DNA adducts or oxidative DNA damage offer supplemental information on the effect of chemical carcinogens to the person’s genetic material. While spontaneous mutations have a certain theoretical and probabilistic effect on cancer incidence, solid tumours seem to develop gradually, offering opportunities for intervention, especially for those with increased susceptibility. Discovering the details of susceptibility via high throughput genomic testing, and tailoring the data to each person, is at the centre of our effort to improve the predictive ability of future cancer development or early detection.

Can you offer examples of the signifi cance of genome-based technologies in determining an individual’s susceptibility to cancers generally?

Today, advanced computational approaches that integrate gene environment interactions in prediction algorithms offer the possibility of personalised risk assessment. The best known example is in the risk assessment of

breast cancer. Testing for polymorphisms in the BRCA genes and integrating this information to certain demographic and medical data offers women the option of making informed decisions about breast cancer risk. Testing for KRAS mutations in colorectal cancer or testing for UGT polymorphisms prior to irinotecan initiation have become the standard of care in genome-based oncology.

What do you perceive to be the wider implications of your research, and how might the risk assessment serve to improve healthcare and, more specifi cally, the prognosis and therapeutic treatment of cancers?

Establishing a solid knowledge base around genetic susceptibility associated with signal transduction and DNA repair is crucial in that it:

• advances the science of molecular risk assessment

• creates valid clinical applications• fuels future research into new therapeutics

targeting the disruption of cancer cell communications and the stimulation of the DNA repair apparatus of normal epithelial cells that operate in toxic, carcinogenic micro-environments

Scientifi c gains are to be followed by improvements in the healthcare delivery system and national health indicators. By incorporating IGF2R and ERCC5 genetic results in risk assessment of epithelial cancer, doctors have – for the fi rst time – access to a genomic computational method that personalises the science of epithelial cancer prediction and early diagnosis. The cost-effectiveness of genomic cancer risk assessment becomes particularly favourable in countries with high tobacco consumption, or countries with high incidence of lung and oral cancers.

In a world of limited healthcare resources, incorporating genomic medicine applications in public health programmes allows screening to be tailored to high risk groups, saving precious resources that can be used to control competing causes of death.

Assessing cancer risks The dedicated research efforts of Dr Athanasios Zavras and his team at Columbia University and Harvard span the best part of two decades. Here, he discusses the background to the development ofan innovative risk assessment method for epithelial cancer, which has exciting therapeutic implications

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DR ATH

ANASIO

S ZAVRAS

38 INTERNATIONAL INNOVATION

Despite advancements in the development of therapeutic treatments for cancer, a preventative cure remains elusive. A report by the National Cancer Institute (NCI) of the United States has revealed that as many as one in two men, and one in three women, will be diagnosed with cancer at some time during their lifetime.

It is perhaps more apparent than ever that research into the underlying causes of the disease and the identifi cation of potential drug targets is essential. Yet the disease still presents enormous challenges to researchers seeking to determine the genetic characteristics and environmental factors that affect an individual’s susceptibility to the disease.

Dr Thanos Zavras and his collaborators in the Division of Oral Epidemiology & Biostatistics at Columbia University’s College of Dental Medicine have invested over 15 years’ worth of research in this fi eld. Through an incremental and carefully-executed process of initial discovery and secondary validation, the team has been able to identify factors which increase the likelihood of an individual developing a tumour of the upper aerodigestive tract (UAC). Furthermore, their fi ndings have been used to form key criteria in an innovative risk assessment method, with direct clinical applications.

IDENTIFY CANCER IN PATIENTS

UAC tumours encompass many epithelial cancers, including lung cancer, cancers of the oral cavity, pharynx, larynx, and the oesophagus. In all, over 2.6 million people globally are affected by UAC; according to the International Agency for Research on Cancer (IARC), in 2008 there were over 270,000 newly diagnosed UAC cancer cases in the U.S., and 400,000 in the EU. Alarmingly, the prevalence of UAC cancers in certain parts of South and East Asia has reached epidemic proportions, overwhelming healthcare systems and placing an unprecedented burden on resources.

A common strategy in curtailing the rate of cancer-related fatalities centres around mass screening. Although statistics remain staggering in terms of the yearly number of deaths caused by cancer, widespread population screening methods have proved successful in controlling the impact of certain cancers. The success of such programmes hinges on the fact that survival rates are closely linked to the stage at which a tumour is identifi ed and subsequent intervention made. Screening facilitates early identifi cation of tumours and thus enables the patient to receive treatment sooner, which increases the likelihood of patient survival.

While screening methods are effective in determining the presence of breast, colorectal, skin and cervical cancers, they are far less successful where other cancers – including those derived in the UAC – are concerned. As such, a major factor underpinning Zavras’s studies involves the way in which screening methods are largely inaccurate in identifying cases of UAC. The impact of this inaccuracy is twofold: fi rstly, there are potentially catastrophic consequences associated with the detection of false positives and false negatives; secondly, the costs involved are colossal and unyielding.

In addressing this issue, Zavras and his colleagues endeavoured to pioneer a screening method exclusively for individuals considered to be of high risk to UAC cancers. By integrating genetic research into traditional epidemiology, Zavras and his team sought to improve the accuracy and cost-effectiveness of risk assessment.

SUSPECT GROWTHFACTORS AND THEIR SIGNALLING

In the late 1990s, Zavras and his colleagues were involved in extensive investigative research in cancer genetics. As part of their studies, the team concentrated on furthering understanding of signal transduction – an intricate complex circuitry through which cancer cells interact and communicate. Their fi ndings would prove essential in formulating the scales and metrics used to determine individual risk to contracting UAC cancers.

The team paid particular attention to two suspected growth factors: Insulin-like Growth Factors 1 and 2 (IGF1 and IGF2), both of which had been previously linked to functions that stimulate the survival of cancer cells and their proliferation. And, through human studies conducted on patients with oral and pharyngeal tumours, the team accumulated evidence to support the hypothesis that cancer risk differs according to the genetic status of the IGF2 receptor. These results were published in Cancer Research (Issue 63, pp. 296–297, 2003) and showed that individuals with a 3’UTR polymorphism in the M6P/IGF2R had a 2.7-fold increased risk of oral cancer compared with individuals with other genotypes (95 per cent confi dence interval: 1.16–6.48). However, Zavras recalls an air of tentativeness regarding the fi ndings. He explains: “At the time of the initial publication we did not know if this was a ‘real’ fi nding, and were cautious in interpreting the results. Also unknown was the exact function of IGF2R in epithelial carcinogenesis”. This fuelled the team to conduct a second study in an attempt to validate their fi ndings, and results confi rmed that individuals with a 3’UTR polymorphism

Epithelial cancer breakthrough A novel risk assessment model has emerged through extensive and concerted research in which Dr Zavras and his team have identifi ed two genes seen to increase an individual’s susceptibility to epithelial cancer

DR ATHANASIOS ZAVRAS

INTELLIGENCE

in IGF2R were at signifi cantly higher risk of contracting upper aerodigestive cancer. Details of the lung cancer fi ndings were published online at Nature Reviews Cancer (2004, Vol.4 (10) short communication). More recently, in 2008, the team characterised the kinetic parameters of tumours with mutated IGF2R and found that the 3’ UTR allelic status confers a higher proliferation index (and higher growth index). Non-small cell lung cancer patients with the 3’UTR polymorphism had faster growing tumours and progressed more rapidly to advanced stages; details can be found in Cancer Letters (Feb 8; 259 (2): 177-85). Subsequently, they evaluated the involvement of IGF2R polymorphisms in the Han population and confi rmed that subjects with mutated variants of the gene have more aggressive forms of cancer, with metastatic spread.

DNA REPAIR AND CANCER

Epithelial carcinogenesis involves several pathways. In 2008, the team made a major breakthrough within the DNA repair pathway. ERCC5, a gene mainly involved in a form of DNA repair known as Nucleotide Excision Repair (NER), was identifi ed as a marker of cancer susceptibility. Nucleotide excision repair is the mechanism upon which the affected nucleotide is removed by a dual incision of the affected strand on both sides of the lesion and fi lling of the resultant gap. ERCC5 or XPG is responsible for the 3’ incision. A phenotypic manifestation of defective ERCC5 is xeroderma pigmentosum, characterised among other things by increased incidence of various types of cancer. Yet, while published reports had implicated the gene in cancer development, it had not been previously linked to UAC.

In a research programme involving 106 individuals with oral premalignant lesions (dysplasia and carcinomas in situ) and 212 healthy controls, Zavras and his collaborators characterised the genotype ERCC5 rs751402. As part of the study, participants provided information on smoking, alcohol use, diet, and demographics, as well as blood samples for DNA analysis.

FINDINGS

The team successfully elucidated fi ndings which identifi ed both environmental and genotype-based markers of epithelial cancers. Statistical analysis found that heavy tobacco use and heavy alcohol consumption increases risk of

early lesions, whereas eating high quantities of fruits was found to be protective. But most signifi cantly, Zavras and his colleagues uncovered seminal results involving ERCC5; they determined that the risk of disease was increased by 89 per cent among individuals positive for ERCC5 rs751402 (95 per cent confi dence intervals:1.1-3.2). Furthermore, individuals carrying the ERCC5 rs751402 T allele had a 26-fold increase in their risk if they used tobacco, an interaction that was statistically signifi cant. Since these discoveries, the role of ERCC5 as a direct risk factor for invasive hepatocellular and upper aerodigestive cancers has been validated through subsequent investigations, carried forth by the enthusiasm and unbridled commitment of the team. The validation studies involved hundreds of cancer patients and healthy controls and showed that when consistently independent of tobacco, individuals with ERCC5-CC experience signifi cant protection against cancer, whereas individuals with the T alleles experience signifi cantly higher cancer risk. Zavras’s fi ndings regarding the ERCC5 gene have thrown up exciting possibilities. The fact that the susceptibility is apparent in the early stage of dysplasia has important clinical implications; integrating ERCC5 data in risk assessment provides a promising tool for the early detection of solid tumours, and a window of opportunity for screening programmes.

RELEVANCE AND APPLICATION

Now that two carefully validated biological markers – seen to signifi cantly increase the probability of an individual contracting epithelial cancer – have been identifi ed, selective screening programmes can be implemented with greater accuracy. It would seem that adults who smoke heavily and are exposed to environmental carcinogens are excellent candidates for such screening. Put simply, integrating ERCC5 and IGF2R data in risk assessment provides a promising tool for the early detection of solid tumours.

In addition, the risk assessment tool can – in the hands of skilful medical counsellors – act as a stimulus in prompting positive behavioural change. In this light, the method might well be appropriated to detract adolescents from smoking, cultivating a shift in attitudes towards smoking in the long-term. This would mark a fi tting legacy to the dedication of Zavras and his team of collaborators.

GENOMICS OF AERODIGESTIVE CANCER RISK ASSESSMENT: PERSONALISED MEDICINE IN ACTION

OBJECTIVES

• To investigate the signifi cance of signal transduction and DNA repair genotypes in relation to epithelial cancers

• To assess evidence of the way in which smoking affects the likelihood of an individual contracting upper aerodigestive tract cancers

• To formulate a cost-effective tool which uses genetic and computational information in screening individuals for upper aerodigestive tract cancers

KEY COLLABORATORS

Professor Vicky Cartsos, Tufts UniversityDr Priyaa Shanmugam, Harvard UniversityProfessor Angela Yoon, Columbia University

FUNDING

National Institute of Dental and Craniofacial Research, NIH, Bethesda

CONTACT

Dr Thanos ZavrasAssociate Professor & Head Division of Oral Epidemiology & Biostatistics Columbia University College of Dental Medicine601 W 168th StreetSuite 34New YorkNY 10032USA

T + 1 212-342 0425F + 1 212-342-8558E az2256@mail.cumc.columbia.edu

DR ATHANASIOS (THANOS) ZAVRAS, directs the Oral Epidemiology Division at Columbia University Medical Center in New York City. He is a full member of the Herbert Irving Cancer Center, and on the faculty of the Harvard School of Public Health. Dr Zavras is a seasoned molecular epidemiologist with over 20 years of experience in the discovery of genomic clinical applications.

FIGURE 1. Prevalence of upper aerodigestive cancers in advanced metstatic stage

Legendper cent with late stage

0% - 27%

28% - 68%

69% - 100%

Cancer patients in county

1 - 116 117 - 430 431 - 898 899 - 2311

TENNESSEE AND KENTUCKY

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