lung cancer & smoking

8/8/2019 Lung Cancer & Smoking

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SMOKING & LUNG CANCER

Ch.BhargaviM.Sc IV Semester

Department of Human Genetics

Andhra University



What is GENETICS?

● “Genetics” is the science of genes, heredity and variations in living organisms.

● It deals with the molecular structure and function of genes,with gene behaviour in thecontext of a cell or organism,

with patterns of inheritance fromparent to offspring, and withgene distribution, variation andchange in populations.



What is a GENE?A gene is the basic physicaland functional unit of heredity. Genes, which aremade up of DNA, act asinstructions to makemolecules called proteins. Inhumans, genes vary in sizefrom a few hundred DNA

bases to more than 2 millionbases. The Human GenomeProject has estimated thathumans have between20,000 and 25,000 genes.



Central Dogma of Molecular Biology



Structure of DNA

● DNA, or deoxyribonucleic acid, isthe hereditary material in humansand almost all other organisms.

● The information in DNA is stored as

a code made up of four chemicalbases: adenine (A), guanine (G),cytosine (C), and thymine (T).Human DNA consists of about 3billion bases, and more than 99percent of those bases are the

same in all people.● DNA is a double helix formed by

base pairs attached to a sugar-phosphate backbone.



Principles of Genetics

● Gregor John Mendel isconsidered the father of Genetics.

● He conducted hybridisation

techniques on pea plants.

● He postulated two laws:

- Law of Segregation

- Law of IndependentAssortment



Mendel's Laws

Law of Segregation (Law of purity of

gametes)

Law of Independent Assortment



Scope of Genetics The potential for understandinghuman genetics increasedgreatly when the HumanGenome Project successfully

identified and mapped all thegenes on human chromosomesin 2003. Genetic techniques canbe used to study individualgenes to learn more aboutspecific disorders.



Recent advances in Genetics

● Human GenomeProject

● Gene Therapy



LUNG CANCER



Lung Cancer Lung Cancer is disease whichconsists of uncontrolled cellgrowth in tissues of the lung.

This growth may lead tometastasis, which is the invasionof adjacent tissue and infiltration

beynd the lungs.



Types of Lung Cancer

There are two main typesof lung cancer, non-smallcell lung cancer and small

cell lung cancer. Thesenames refer to how thecancers look under amicroscope to apathologist.Most cancers

are non-small cell.



Non-Small Cell Lung Cancer

Non-small cell lung cancer accountsfor at least 80% of lung cancers in theUnited States. It does not spread asrapidly as small cell lung cancer, but isstill frequently diagnosed after asurgical cure is not possible. Smokingis the leading cause of lung cancer, but

factors other than smoking are morelikely to contribute to this type of lungcancer. There are 3 primary types of non-small cell lung cancer.

– Adenocarcinoma

– Squamous cell carcinoma

– Large cell carcinoma



Small Cell Lung Cancer

Small cell lung cancer ( oat cell carcinoma)accounts for 15% of lung cancers. Unlike themore common non-small cell lung cancers,small cell lung cancer grows rapidly, but oftenresponds well to chemotherapy initially.Unfortunately, it tends to become moreresistant to treatment as the diseaseprogresses.

They usually begin in the large airways(bronchi) of the lungs, but spread early, often tothe brain. They are broken down into only twostages, limited and extensive stages. 60 to 70%of people already have extensive stage diseaseat the time of diagnosis.

Most cases are due to smoking, although other

causes can contribute as well. This type of lungcancer is more common in men than in women,and is the most common type of lung cancer tohave symptoms referred to as paraneoplasticsyndrome -- that is, symptoms due tohormones secreted by a tumor or by the body’simmune response to a tumor.



Lung Cancer Types

Nonsmall cell carcinoma (85%) includessquamous, adenocarcinoma, and large cellcarcinoma. Of these adenocarcinomas has

superseded squamous as the most common type. If detected early, these may be treated surgically.

Small cell carcinoma (15%) characterized by rapidgrowth and dissemination. Treated withchemotherapy and radiation therapy.



Symptoms of Small Cell Cancer

Symptoms of small cell lung cancer include

* Persistent cough

* Coughing up blood (hemoptysis)

* Swelling in the face and neck

* Shortness of breath

* Wheezing

* Repeated episodes of pneumonia or

bronchitis* Hoarseness

* Fatigue

* Weight loss



Causes of Lung Cancer ● The most common cause of lung cancer is

smoking.

●

Smoking causes lung cancer because there aresubstances within tobacco that are known tocause cancer. These substances are known ascarcinogens, that cause the actual damage tothe cells in the lungs. A cell that is damaged maybecome cancerous over a period of time.

● One cannot predict which smoker is at greater risk of developing lung cancer. In general,

though, a smoker's chances of developingcancer depends on:

* The age that the person began smoking

* How long the person has smoked

* How many cigarettes per day the personsmokes

● Passive smoking - breathing in someone else'ssmoke - may also increase the risk for developing lung cancer.



Other factors that increase the risk of lung cancer include

- exposure to asbestos and some other substances, such as arsenic or drinking water thatcontains high levels of arsenic, chromium and nickel, especially if you are a smoker

- exposure to radon gas and repeated x-rays

- having had lung cancer before

- family history of lung cancer

- air pollution



Screening for Lung Cancer

In the US, 25% of the population smokes. The lifetime riskof developing lung cancer in smokers is approximately 10%.More than 170,000 new patients are diagnosed each year with lung cancer.

●Screening

Routine screening for lung cancer with chest radiography or sputum cytology in asymptomatic persons has been

abandoned because the yield of chest x-ray screening is low(0.4% cancer).

●.CT Screening

Nonrandomized trials have shown that CT may be useful inlung cancer screening. CT nearly doubles the percentagewith Stage I disease..

● CT Cost - Multiple CT examinations

CT screening is costly. Depending on the geographic locale,up to 60% of screened individuals may have a nodule whichmay be malignant. Determining whether such nodules aremalignant requires multiple CT examinations over severalmonths to make sure that the nodule does not grow.



Lung Cancer in India

● Lung cancer is one of thecommonest malignantneoplasms all over the world.It accounts for more cancer deaths than any other cancer.It is increasingly beingrecognized in India.

● With increasing prevalence of smoking, lung cancer hasreached epidemic proportionsin India.



Lung Cancer due to Smoking

Lung cancer is directlyrelated to smoking. Over 40carcinogens have beenidentified in cigarette smoke.

The risk of developing lungcancer is directly related tothe number of cigarettessmoked. The change inconsumption from unfilteredhigh tar cigarettes to filteredlow tar cigarettes parallelsthe change in incidence fromsquamous cell carcinoma toadenocarcinoma.



T b i th l di f



Tobacco Facts

Tobacco use is the leading cause of preventable illness and death in the United States.It causes many different cancers and chronic lungdiseases, such as emphysema and bronchitis, andheart disease.

* Cigarette smoking causes an estimated443,000 deaths each year, including approximately49,400 deaths due to exposure to secondhandsmoke.

* Lung cancer is the leading cause of cancer death among both men and women in the UnitedStates, and approximately 90% of lung cancer

deaths among men and 80% among women aredue to smoking.

* Smoking causes many other types of cancerslike that of the throat, mouth, nasal cavity,esophagus, stomach, pancreas, kidney, bladder,and cervix, and acute myeloid leukemia.

* People who smoke are up to six times morelikely to suffer a heart attack than nonsmokers, andthe risk increases with the number of cigarettessmoked. Smoking also causes most cases of chronic lung disease.



Genetics of Lung Cancer

Lung cancer is initiated by activation of oncogenes or inactivation of tumor suppressor

genes. Mutations in the K-ras proto-oncogene are responsible for 10–30% of lungadenocarcinomas. Mutations and amplification of EGFR are common in non-small celllung cancer. Chromosomal damage can cause inactivation of tumor suppressor genes.Damage to chromosomes 3p, 5q, 13q, and 17p are particularly common in small celllung carcinoma. The ''p53'' tumor suppressor gene, located on chromosome 17p, is

affected in 60-75% of cases

.

Several genetic polymorphisms associated with lung cancer include polymorphisms ingenes coding for interleukin-1, cytochrome P450, apoptosis promoters such as

caspase-8 and DNA repair molecules such as XRCC1. People with thesepolymorphisms are more likely to develop lung cancer after exposure to carcinogens.A recent study suggested that the MDM2 309G allele is a low-penetrant risk factor for

developing lung cancer in Asians.



Markers in consideration

CYP 1A1

Alu ACE



Tumour Markers

●

Tumor markers are substances produced by tumor cells or by other cellsof the body in response to cancer. Different tumor markers are found indifferent types of cancer. Tumor marker levels are not altered in all peoplewith cancer, especially if the cancer is early stage.

● Tumor markers are used in the detection, diagnosis, and management of some types of cancer. They may suggest cancer, but this alone is usually

not enough for diagnosis. Therefore, measurements of tumor markers areusually combined with other tests, such as a biopsy, to diagnosecancer.Tumor marker levels may be measured before treatment to helpdoctors plan appropriate therapy. In some types of cancer, tumor marker levels reflect the stage (extent) of the disease.They may also be used tocheck how a patient is responding to treatment. A decrease or return to a

normal level may indicate that the cancer is responding to therapy,whereas an increase may indicate that the cancer is not responding. After treatment has ended, they may be used to check for recurrence.



CYP 1A1

● The CYP1A1 category of enzymes playsa central role in the metabolic activation of major tobacco carcinogens. Severalpolymorphisms within the CYP1A1 locus

have been identified and have beenshown to be associated with lung cancer risk, particularly in Asian populations.TheCYP1A1m1 and CYP1A1m2 variantswere significantly associated with lungcancer susceptibility. This risk wasprominent in case of SCC.

● CYP1A1m1 and m2 polymorphisms areassociated with the smoking related lung

cancer risk in Kashmiri population.

● Mutation is observed in this marker.

T d l bl d l h t t h P450 1A1 (CYP1A1) i CYP1A1 RNA



To develop blood lymphocyte cytochrome P450 1A1 (CYP1A1) expression, CYP1A1 mRNA

expression and its associated catalytic activity in freshly prepared blood lymphocytes isolated fromhealthy controls and patients suffering from tobacco induced lung cancer are characterised. Humanblood lymphocytes were found to express CYP1A1 mRNA and significant activity of 7-ethoxyresorufin-O-deethylase (EROD). Significant increase in the activity of EROD and CYP1A1mRNA was observed in blood lymphocytes isolated from patients suffering from lung cancer. Further,

controls with variant genotypes of CYP1A1 (Msp1 or Ile/Val polymorphism) exhibited significantincrease in the enzyme activity associated with an increase in CYP1A1 mRNA expression whencompared to the controls with wild type genotype. Patients with variant genotypes of CYP1A1 alsoexhibited much greater increase in the blood lymphocyte CYP1A1 mRNA expression and ERODactivity when compared to controls or patients with wild type genotype.

This data thus provides evidence of CYP1A1 expression in freshly isolated bloodlymphocytes and differences in reactivity in

individuals with variant genotypes of CYP1A1, suggesting that blood lymphocyte CYP1A1expression profile could help in identifyingindividuals at risk to environment induced lungcancer.



Alu ACE

Cancer mortality increased significantlywith increasing current smoking levels.Although no clear relationship was observedbetween ACE genotypes and fatal cancer,the interaction term between currentsmoking and ACE genotype DD was foundto be significant. In stratified analysis byACE genotype after controlling for age, sex,alcohol intake, body mass index, glucoseintolerance, serum total cholesterol andsystolic blood pressure, the risk of fatalcancer in currently smoking subjects withgenotype DD was twofold greater than thatin subjects with genotypes II and ID. Amongcurrent smokers, subjects with genotype DD

also showed a significantly greater risk of death due to cancer compared with thosewith genotypes II and ID combined. ACEgenotype DD enhances the associationbetween smoking and cancer death in thegeneral population.

Angiotensin-converting enzyme (ACE) playsan important role in the physiological controlof blood pressure and inflammation. Aninsertion/deletion (I/D) polymorphism of thegene for ACE in relation to cardiovascular,cerebrovascular, neurodegenerative, andinflammatory diseases is observed. There isa possible association between lung cancer and insertion/deletion polymorphism of theACE gene. Patients with lung cancer andcontrol subjects are studied. ACE I/Dgenotypes were determined by PCR. Allelicfrequencies and genotype distribution of theACE I/D polymorphism in the patient groupwould be significantly different from controlsubjects. This suggests that the ACE I/Dpolymorphism could be a risk factor for patients with lung cancer

Familial Aggregation of Lung Cancer



Familial Aggregation of Lung Cancer Although the major risk factor for lungcancer is cigarette smoking, it is alsotrue that only 15% of life time smokersget lung cancer. This indicates that

other factors which may affect the roleof cigarette smoking are also importantin the development of lung cancer.

In addition to life style andenvironmental causes the geneticconstitution of an individual also hasan important role in lung cancer predisposition or protection from it. Apossible role for genetic susceptibilityin the development of lung cancer hasbeen inferred from familial clustering of the disease.

It has been known for more than 40 years that family

history is also an independent risk factor for lung cancer,

in addition to tobacco smoking, The first report on familial

aggregation of lung cancer appeared as early as in

1963. Actually, the importance of family history and

genetic susceptibility to lung cancer has often been

overlooked mainly because cigarette smoking is such

an overwhelming and preventable risk factor. Most

of the earlier epidemiological researchers believed

that the similar smoking environment within the fam-

ily setting or workplace accounted for those find-

ings of aggregation of lung cancer cases in families.

The presence of family history of lung cancer in first degree relatives had been



This study also reported that non-smokers with lungcancer were 40% more likely thannonsmoking controls to report a first degree relativewith lung cancer. Women were more likely than mento report such a family history. Studies clarified thateven after adjusting for smoking patterns,individuals with a family history of lung cancer were

at approximately two to threefold increased risk of developing this disease. Available evidencesupports the view that family history of lung cancer isassociated with increased risk for lung cancer in bothsmokers and nonsmokers. The risk was higher if therelative was a woman.

p y y g greported to confer an excess risk of 30% and the familial aggregation was found tobestronger in the subset of patients with adenocarcinoma of the lung.

All these findings suggested a genetic predisposition to lung cancer after taking intoaccount the familial clustering of smoking habits, family size and age structure. Thefindings of a stronger aggregation when the onset of disease is at an early age areindicative of an inherited component to risk. Consistent epidemiologic data and resultsof lung cancer linkage studies have suggested that family history should also be includedas a high risk factor for lung cancer.



Early onset of Lung Cancer in Non-Smokersin Families

Exposure to environmental tobacco smoke (ETS) is consideredto be a major lung cancer risk factor fo non smokers. Youngage at diagnosis often suggests an underlying genetic

contribution to risk and several studies have shown that familyhistory of an early onset lung cancer is associated withincreased risk of lung cancer among never smoking relatives.

The association between familial history of lung cancer andlung cancer in non smokers was reported to be stronger inpatients younger than 60 years and patients withadenocarcinoma.



Genetic Diagnosis

U f G ti S tibilit I f ti



Use of Genetic Susceptibility Informationin Smoking Prevention and Cessation

People who quit smokiinglive longer than those who continue tosmoke and smokers who quit before age50 cut their risk of dying in the next 15years in half compared to those whocontinue to smoke. With smokingcessation, the risk of lung cancer

decreases over time. The amount of timeit takes to reach the risk of a non smoker depends on the number of years smokingcessation as well as the number of cigarettes smoked per day. The morecigarettes smoked per day, the longer ittakes to reach a level of risk close to that

of a non smoker. Ex-smokers never reachthe same low level of risk as a non-smoker. At each encounter with ahealthcare provider,

All smokers should be encouraged toquit smoking.

Strategies available to assist withcessation include nicotinereplacement therapies, drug therapy,and psychological therapies that

include social support in a groupsetting. A combination of strategieswith the inclusion of psychologicalsupport has proven to be the mostsuccessful approach. Furthermore,knowledge of genetic susceptibility for lung cancer could be used to identifypersons at risk and to individualizetreatments, such as chemoprevention



Brief Process and Methodology

● Isolation of DNA

● Quantitative and Qualitative Analysis

● PCR amplification● Electrophoresis

● Analysis



Quantitative and Qualitative Analysis

Spectrophotometer Shearing of DNA

PCR amplification



PCR amplification

The purpose of a PCR (Polymerase Chain Reaction) is to

make a huge number of copies of a gene

El t h i & A l i



Electrphoresis & Analysis

St d id ti



Study consideration

✔ Present study deals with normal healthy individuals,smokers and Lung cancer patients.

✔ Blood samples of the above are taken and studied.

✔ The project is mainly to observe the prevalance of

mutations or deletions in the DNA of smokers that arefamiliar with that of the lung cancer patients.



Smoking cessation helps fight against LUNG CANCER

lung cancer & smoking

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