Genetic variations and head and neck cancer risks

Nosheen Masood • Azra Yasmin • Mahmood Akhtar Kayani

Received: 18 March 2013 / Accepted: 11 January 2014 / Published online: 23 January 2014

� Springer Science+Business Media Dordrecht 2014

Abstract Variations in CYP1A1, GSTM1, GSTT1 and

GSTP1 in head and neck cancer have been frequently

found in literature. But these studies give an overview of

these genetic variations in different populations. The cur-

rent mini review focus on the analysis of these genetic

variations at DNA, mRNA and protein levels in the same

study group. Eight publications were reviewed on the same

study samples yielding results at DNA, mRNA and protein

levels. At DNA level, CYP1A1 showed significantly higher

mutations in head and neck cancer patients compared to

controls at g.2842A[C and g.2842_2843insT. GSTM1 and

GSTT1 showed deletion polymorphisms and heterozygous

deletion confers protection against cancer. Mutations were

also found in GSTP1 at g.2848A[T, g.2849G[A,

g.1074delC and g.1466delC. mRNA and protein expres-

sional analysis revealed underexpression of CYP1A1, loss

or underexpression of GSTM1 and GSTT1 and overex-

pression of GSTP1. In addition an unusual intronic variant

of GSTP1 mRNA was also found, retaining the intronic

portion between exons. The current review gives a com-

plete study overview regarding CYP1A1, GSTM1, GSTT1

and GSTP1 variations at DNA, mRNA and protein levels in

head and neck cancer. The review is helpful in designing a

new experiment or gene therapy for head and neck cancer

patients.

Keywords GSTM1 � GSTT1 � Head and neck cancer �DNA � Protein � mRNA � Polymorphisms � Variations

Introduction

Incidence of head and neck cancer has increased at an

alarming rate for the past 10 years [1]. Both environmental

as well as genetic factors are associated with its initiation

and progression [2]. Many genes involved in carcinogen

detoxification have been studied in relation to head and

neck cancer. Carcinogen detoxification takes place in two

phases: phase I involves either the conversion of carcinogen

into water soluble form for excretion or changing the car-

cinogen into more electrophilic compound. These inter-

mediate electrophilic compounds are recognized by the

phase II detoxification enzymes. Phase II enzymes finally

route them out of the body or render them harmless [3].

Phase I includes cytochrome P 450 (CYP) enzymes like

CYP1A1 and CYP1A2 and phase II includes mainly glu-

tathione S transferases like GSTM1, GSTT1, GSTP1 and

GSTA Polymorphisms in CYP1A1 have been frequently

studied in head and neck cancer initiation and contradictory

reports are found [4]. Four different polymorphisms in

CYP1A1 sequence have been reported; CYP1A1*2 involves

a T6235 to C transition in 30 noncoding region, CYP1A1*3

involves a A4889 to G transition in exon 7, CYP1A1*4

involves a T5639 to C transition in intron 7 and CYP1A1*5

involves a C4887 to A transition in exon 7 [5]. Similarly

GSTM1 and GSTT1 studies regarding head and neck cancer

have found associations with cancer. Three variants of

GSTM1 have been reported; deletion of entire gene,

GSTM1a and GSTM1b that differ by C534 to G substitution.

For GSTT1 two alleles have been reported one functional

and other nonfunctional.

N. Masood (&) � A. Yasmin

Environmental Sciences Department, Fatima Jinnah Women

University, Rawalpindi, Pakistan

e-mail: nosheenmasood@hotmail.com

M. A. Kayani

Department of Biosciences, COMSATS Institute of Information

Technology, Islamabad, Pakistan

123

Mol Biol Rep (2014) 41:2667–2670

DOI 10.1007/s11033-014-3125-6

Two polymorphic alleles for GSTP1 have also been

reported in literature GSTP1*B, GSTP1*C along with wild

type GSTP1*A. Both alleles present an A-to-G transition at

nucleotide 313 (codon 104), causing an isoleucine-to-

valine change. The GSTP1*C allele presents a C-to-T

transition at nucleotide 341 (codon 113), in addition to the

substitution at nucleotide 313, that changes alanine to

valine [6].

The expressional variations have also been found in

these genes [7]. CYP1A1, GSTM1, GSTT1 and GSTP1

mRNA had overexpression and also underexpression

varying with population under study giving contradictory

reports. Similarly CYP1A1, GSTM1, GSTT1 and GSTP1

protein expression is also reported to show variations in

head and neck cancer patients [7, 8].

A number of review papers are available that give an

overview about the polymorphisms related to these genes

[4, 9]. Some of them also give an insight into population

trends associated with these polymorphisms. But none of

them discuss about the genetic polymorphisms, mRNA and

protein expressional variations at one time. Therefore the

current review is related to the analysis of CYP1A1,

GSTM1, GSTT1 and GSTP1 in head and neck cancer and

association of these genes with variations at DNA, mRNA

and protein levels. The novelty of this review lies in that

the complete research is carried out on the similar study

group and published in eight full length research articles.

Method

Pubmed, MEDLINE, NCBI, were searched with the key-

words GSTM1, GSTT1, GSTP1, CYP1A1, Head and neck

cancer, genetic variations, expressional variations, IHC,

SNP and polymorphisms. Only those studies were selected

that were on the same study population (same country)

others were not mentioned. Confusing data were rechecked

by all the authors and duplication was avoided. Only

published reports were selected. At the end on exclusion

and inclusion criteria the mini review consists of eight

research papers dealing with CYP1A1, GSTM1, GSTT1 and

GSTP1 polymorphisms [3, 10–16] (Fig. 1). The research

papers are on head and neck cancer and from Dec 2010 to

Nov 2012. The study subjects are from the same country in

all the papers so that we can easily conclude the effect of

DNA polymorphisms on mRNA and protein expression

and also at the same time study any novel variation at

DNA, mRNA and protein levels. All these studies are

carried out on head and neck cancer along with its su-

banatomic sites. The DNA polymorphisms are studied

from blood specimen whereas mRNA and protein varia-

tions from tumor tissues. All the studies clearly defined

about the control specimens. Odds ratio (OR) and its 95 %

confidence interval (CI) were assessed for each study.

P value \0.05 was considered statistically significant, and

0.05 B P \0.10 was indicated suggestive. SPSS software

was used for statistical analysis.

Results

For studies related to DNA polymorphisms 388 head and

neck cancer patients and 150 controls were screened. The

cancer of oral cavity was more common (P \ 0.01) than

pharynx and larynx. Male to female ratio was statistically

nonsignificant. Mean age of head and neck cancer patients

was 48 (±16.59) and cancer free normal healthy control

was 46 (±17.69). Tobacco users are more prone to head

and neck cancer than nontobacco users as was apparent

from these studies.

Variations in CYP1A1

CYP1A1 have been found to show novel mutations in head

and neck cancer patients compared to controls. A novel

substitution mutation was observed resulting in A2842 to C

mutation causing tyrosine to serine formation [11]. Another

novel frameshift mutation was found in head and neck

cancer patients. This mutation involves the insertion of T

between nucleotide 2842 and 2,843. This insertion causes a

change in the remaining sequence and resulted in altered

protein structure [13]. For mRNA expressional analysis 49

head and neck cancer tissues along with 49 controls were

studied. The results revealed statistically significant

(OR 4.5, CI 1.5–13.4) underexpression of CYP1A1 mRNA

compared to adjacent control tissue [12]. Similarly for

protein expression analysis it was found that significant

number of patients had underexpression compared to

controls [15] (Table 1).

Variations in GSTM1 and GSTT1

GSTM1 and GSTT1 DNA analysis revealed that these

genes are found to be frequently deleted showing null

polymorphism in head and neck cancer patients. These null

polymorphisms were found to be significantly higher

(OR 2.3, CI 1.5–5.5; OR 2.04, CI 1.3–3.1 respectively) in

patients compared to controls. Novel method of deletion

mapping was used that showed the exact nucleotides of

start and end of deletions. GSTM1 was found to be deleted

from 98 bp upstream and 293 bp downstream the gene

whereas GSTT1 was deleted 537 bp upstream and 333 bp

downstream the gene [10]. In addition to mapping, heter-

ozygosity of GSTM1 and GSTT1 deletions were also

studied using a novel method. It was found that GSTM1

and GSTT1 were nonsignificantly associated with head and

2668 Mol Biol Rep (2014) 41:2667–2670

123

neck cancer risk [16] (Table 1). mRNA of GSTM1 and

GSTT1 showed underexpression in significantly higher

(OR 4.5, CI 1.5–13.4; OR 3.2, CI 1.1–9.6) number of head

and neck cancer patients compared to controls [12]. Sim-

ilarly protein expression was also reduced in head and neck

cancer patients compared to controls [15].

Variations in GSTP1

At DNA level novel mutations were found in the GSTP1.

Two substitution mutations A2848 to T and G2849 to A were

found in the GSTP1 in head and neck cancer patients. First

one was sense mutation resulting in leucine to leucine

formation and second was nonsense mutation resulting in

alanine to threonine formation. In addition two intronic

deletions of C were also found at nucleotide 1,074 and

1,466 [13]. Overexpression of GSTP1 mRNA was observed

in significantly (OR 4.2, CI 1.2–15.3) higher number of

Records identified through

database searching

(n = 89 )S

cree

nin

gIn

clu

ded

Elig

ibili

tyId

enti

fica

tio

n Additional records identified

through other sources

(n = 75 )

Records after duplicates removed

(n = 25 )

Records screened

(n = 25 )

Records excluded

(n = 14)

Full text articles assessed

for eligibility

(n = 11)

Full text articles excluded,

with reasons

(n = 3 )

Studies included in

qualitative synthesis

(n = 8)

Studies included in

quantitative synthesis

(meta analysis)

(n=8)

Fig. 1 Schematic flowchart showing selection of studies and exclusion of studies

Table 1 Variations reported in CYP1A1, GSTM1, GSTT1 and GSTP1

genes in head and neck cancer at DNA, mRNA and protein levels

Head

and

neck

cancer

DNA mRNA Protein

CYP1A1 g.2842A[C Underexpression Underexpression

g.2842_2843insT

GSTM1 Deletion Loss of

expression/

underexpression

Loss of

expression/

underexpression

GSTT1 Deletion Loss of

expression/

underexpression

Loss of

expression/

underexpression

GSTP1 g.2848A[T Overexpression Overexpression

g.2849G[A

g.1074delC

g.1466delC

Mol Biol Rep (2014) 41:2667–2670 2669

123

patients compared to controls [12]. During mRNA

screening a novel intronic variant was also observed that

was concluded to be due to unusual splicing retaining the

intronic portion. The result was a stable mRNA obtained

during screening of mRNA levels of respective gene [14].

Similarly GSTP1 protein expression was also elevated in

head and neck cancer tumor tissues compared to normal

tissue [15] (Table 1).

Discussion and conclusion

The current mini review focuses on eight major publica-

tions regarding to CYP1A1, GSTM1, GSTT1 and GSTP1 in

head and neck cancer [3, 10–16]. All these publications

were on the same study samples. Novel mutations have

been reported in these research papers in CYP1A1 at DNA

levels and underexpression was observed for mRNA and

protein levels [11, 13]. For GSTM1 and GSTT1 null poly-

morphism was observed but novel method of deletion

mapping and heterozygosity was introduced [3, 10]. It was

revealed that heterozygous status of GSTM1 and GSTT1

deletion confers protection against head and neck cancer

incidence [16]. GSTP1 also revealed novel mutations in the

coding as well as noncoding regions [13]. GSTP1 mRNA

and protein was overexpressed in tumor tissues compared

to controls [12, 15]. An unusual intronic retention was

observed in the mRNA due to splicing variation in GSTP1

[14]. Underexpression and overexpression was correlated

with stages of head and neck cancer [12]. GSTP1 overex-

pression has been considered not only related to genotypic

variations but also to a number of different mechanisms

including gene amplification, transcriptional activation,

protein stabilization, and genetic abnormalities [17].

Although a number of reviews have been published

discussing about the polymorphisms in these genes with

reference to head and neck cancer but none of them are on

the same study group [4, 7]. The current review gives an

overview about the role of CYP1A1, GSTM1, GSTT1 and

GSTP1 in head and neck cancer risk in an elaborative way.

The mutations at DNA level do contribute at mRNA and

protein expression as depicted from the current review.

Therefore before designing a new experiment or gene

therapy the current review may be studied.

Acknowledgments All the persons who supported this review are

acknowledged.

Conflict of interest No conflict of interests in the study and no grant

or funding provided by any source.

References

1. Parkin DM, Whelan SL, Ferlay J, et al (2002) Cancer incidence in

five continents, vol. VIII. IARC scientific publications No. 155,

Lyon: IARC

2. Jensen CA, Hu JJ, Case LD et al (2010) Stress and depression in

head and neck cancer patients by primary surgery versus primary

radiotherapy treatment modality. J Clin Oncol 28:15s

3. Masood N, Kayani MA, Malik FA et al (2011) Genetic variations in

carcinogen metabolizing genes associated with head and neck cancer

in Pakistani population. Asian Pac J Cancer Prev 12:491–495

4. Hiyama T, Yoshihara M, Tanaka S et al (2008) Genetic poly-

morphisms and head and neck cancer risk (review). Int J Oncol

32(5):945–973

5. Jun T, Ming Y, Xin N et al (2010) Genetic polymorphisms in

cytochrome P450 genes are associated with an increased risk of

squamous cell carcinoma of the larynx and hypopharynx in a

Chinese population. Cancer Genet Cytogenet 196:76–82

6. Zimniak P, Nanduri B, Pikula S et al (1994) Naturally occurring

glutathione S-transferase GSTP1 isoforms with isoleucine and

valine in position 104 differ in enzymic properties. Eur J Bio-

chem 224:893–899

7. Smart J, Daly AK (2000) Variation in induced CYP1A1 levels,

relationship to CYP1A1, Ah receptor and GSTM1 polymor-

phisms. Pharmacogenetics 10:11–24

8. Anttila S, Tuominen P, Hirvonen A et al (2001) CYP1A1 levels in

lung tissue of tobacco smokers and polymorphisms of CYP1A1 and

aromatic hydrocarbon receptor. Pharmacogenetics 11:501–509

9. Geisler SA, Olshan AF (2001) GSTM1, GSTT1, and the risk of

squamous cell carcinoma of the head and neck: a mini-HuGE

review. Am J Epidemiol 154(2):95–105

10. Masood N, Ishrat M, Malik FA et al (2010) Association of

GSTM1 and GSTT1 gene deletions with risk of head and neck

cancer in Pakistan: a case control study. Asian Pac J Cancer Prev

11:881–885

11. Masood N, Malik FA, MahJabeen I et al (2011) A novel CYP1A1

gene polymorphism and the risk of head and neck cancer in

Pakistani population. Afr J Biotechnol 10(27):5273–5280

12. Masood N, Malik FA, Kayani MA (2011) Expression of xeno-

biotic metabolizing genes in head and neck cancer tissues. Asian

Pac J Cancer Prev 12:377–382

13. Masood N, Kayani MA (2011) Mutational analysis of xenobiotic

metabolizing genes (CYP1A1 and GSTP1) in sporadic head and

neck cancer patients. Genet Mol Biol 34(4):533–538

14. Masood N, Malik FA, Kayani MA (2012) Unusual intronic var-

iant in GSTP1 in head and neck cancer in Pakistan. Asian Pac J

Cancer Prev 13:1–4

15. Masood N, Kayani MA (2012) Expression patterns of carcinogen

detoxifying genes (CYP1A1, GSTP1 & GSTT1) in HNC patients.

Pathol Oncol Res 19(1):89–94

16. Masood N, Kayani MA (2012) Protection against laryngeal and

pharyngeal carcinoma: heterozygous versus homozygous dele-

tions of GSTM1 and GSTT1. Genet Mol Biol 36(1):1–6

17. Matthias C, Bockmuhl U, Jahnke V, Harries LW, Roland WC,

Peter JW, Julie A, Stephen WF, Philip H, Anthony A, Richard CS

(1998) The glutathione-S-transferase GSTP1 polymorphism:

effects on susceptibility to oral/pharyngeal and laryngeal carci-

nomas. Pharmacogenet 8:1–6

2670 Mol Biol Rep (2014) 41:2667–2670

123