How does smoking cause cancer?

When a cell divides by mitosis, it is usually controlled by cell cycle checkpoints. If a cell has abnormalities it can start uncontrollably dividing, producing a mass of abnormal cells called a tumour.  Tumours can be benign (doesn’t spread), or malignant. Malignant tumours are cancerous and can grow into surrounding tissue, including organs, affecting the usual function of the body. These cancerous cells can break away from the tumour and travel through the blood or lymphatic system to other parts of the body, creating secondary tumours called metastases. There are over 200 types of cancer, but the most common are breast, lung, prostate and bowel cancer.

The biggest, and most preventable, cause of cancer is smoking. It is responsible for about 75–80% of lung cancers- the most common type of cancer, with one of the lowest survival rates. Cancer causing chemicals are known as carcinogens. Cigarettes contain more than 70 carcinogens, for example, benzene, polonium-210, benzo(a)pyrene and nitrosamines. Once they enter the body, cytochrome P-450 enzymes catalyse the process of metabolic activation, which enables them to bind covalently to DNA, forming DNA adducts. A build-up of DNA adducts causes insertion mutations because it stops DNA polymerase processing the DNA correctly during DNA replication. This leads to a frameshift mutation which can ultimately result in cellular proliferation and cancer.

References:

Alison C. MacKinnon, Jens Kopatz, Tariq Sethi (2010) The molecular and cellular biology of lung cancer: identifying novel therapeutic strategies, British Medical Bulletin, 95(1), 47-61

(2010) How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General. NCBI

Stephen S. Hecht (1999) Tobacco smoke carcinogens and lung cancer. Journal of the national cancer institute, 91(14), 1194-1210

How smoking causes cancer. Cancer research

Cancer, NHS

An introduction to oncology…

Cancer seems to be one of the diseases which cannot be uttered without a trace of compete terror. Perhaps this is because it is so familiar to us- 1 in 2 people in the UK will be diagnosed with cancer in their life.  Most of us, then, at least knows, or has known someone who has cancer, and has seen the devastation it can cause. I, however, lucky enough to be not be in this majority, have grown up only hearing about cancer through books and television. It first came as a shock to me then, on my work experience in palliative care and an oncology ward, seeing how cancer can leave a person so vulnerable.

As I stepped into the room, I instantly felt that I was disrupting something so massively personal and private that it was insulting for me to be there. The patient was laying on the hospital bed, writhing in pain, her skin gaunt and jaundice- a classic sign of her terminal pancreatic cancer. There was a bed on the floor next to hers, and sat on it, her husband- elbows resting on his knees, and hands holding his weeping head. Bizarrely, I found it equally distressing to see a fully grown man completely broken, and a woman delusional in pain.

It seems dismissive of me to use such intense suffering as a lesson; horrible even to think that this experience heightened my interest in oncology. However, it has. Oncology intrigues me both as a science, and as a potential to support people in some of the most important and terrifying moments of their life. As my interest grows, I’ve done more research.

Should assisted suicide be legalised?

The debate about legalising assisted suicide is an increasingly relevant and controversial topic among both medics and the public. It is also one I have accounted multiple times during work experience and volunteering in palliative care. It further must be discussed to protect both doctors from being sued and vulnerable patients.

To start I would like to make clear some basic definitions. Assisted suicide or assisted dying is the deliberate act or encouraging in assisting someone to commit suicide. Euthanasia differs in that it is the deliberate act of ending someone’s life to stop suffering. Currently the UK law states that all acts or euthanasia and assisted suicide are illegal, with euthanasia being treated as murder or manslaughter, and a maximum of 14 years for assisted suicide.

However, there is a call to the change the UK laws. In multiple countries, for example Belgium, Luxembourg, The Netherlands, Switzerland and some states of America, there are acts that legalise the assisted dying of terminally ill patients. One of the most successful schemes is Oregon’s dying with dignity act. It allows physicians to prescribe lethal doses of a drug (usually a barbiturate) to citizens of Oregon who are over 18, terminally ill with a prognosis of less than 6 months to live, and are proven to be mentally competent. In Oregon’s annual report it states that the top three reasons patients request assisted suicide are due to loss of autonomy (89.5%), loss of dignity (65.4%) and the loss of ability in engaging in activities that make life enjoyable (89.5%). It seems compassionate to allow terminally ill adult patients to have control and dignity over their death, which is guaranteed to be safe and peaceful by assisted dying. Many of these people would instead commit suicide in their homes, risking a painful and gruesome death, or instead have to travel to Switzerland to do this, spending around £10,000. Making assisted dying illegal therefore seems disrespectful and unreasonable  when (according to the dignity in dying British campaign group) 82% of the public would support to legalise assisted dying for the terminally ill, and schemes around the world show that it can realistically work without being violated. So, why is it still illegal?

Firstly, and perhaps most importantly, patients may agree against their will to assisted dying due to pressures from family, caregivers and doctors. This is backed by Oregon’s research which stated that in 2017 65% of those that requested assisted dying did so because they felt they were a burden on their family. In this perspective encouraging people to commit suicide therefore seems unethical. This is largely backed by The British Medical Association and the Royal College of General Practitioners, who share the view that assisted dying would be contrary to the ethics of clinical practice, as the principal purpose of medicine is to improve a patient’s quality of life, not to intentionally foreshorten it. Religious people also generally see suicide as a sinful act as all life is sacred so must not be deliberately ended.

Further, assisted suicide requires self-administration of a drug often taken orally. This prevents those who are incapacitated from being granted help to die. Surely everyone will a terminally illness should have the same rights? This raises the question if assisted suicide is legalised, should voluntary euthanasia be legalised? From these questions, many people worry that legalising assisted suicide will lead to a ‘slippery slope’ towards widespread euthanasia, where euthanasia becomes a cheap alternative to palliative care and the vulnerable are exploited. There is also worry that introducing assisted suicide into the UK will downgrade palliative care.

In summary, it is obvious that there is no clear answer to: is assisted suicide right or wrong, and can it be safely introduced into the NHS? It is not a question that should be taken lightly, however I think there is great importance in raising awareness about the debate, and seriously considering a change in the law.

IQ- nature or nurture?

As an aspiring medical student, I am preparing to take the UKCAT exam this summer. Whilst practising a mock paper my immediate thought was that it is similar to an IQ test. This intrigued me and lead me to question the nature of IQ and, more specifically, if it is derived from genetics or environmental factors.

IQ, which stands for Intelligence Quotient, is a method of measuring the abstract nature of intelligence. It aims to score an individual on their general cognitive ability, or the general factor of intelligence written as “g”, from a series of standardised tests. These scores are also closely correlated with other aspects of life such as health, happiness, choice of romantic partner and longevity.  This is because the same variant of a gene can have a positive effect on intelligence, but a negative effect on a different trait, for example seven genes for intelligence are also associated by a negative correlation with schizophrenia.

The ‘Twins Early Development Study’, conducted by Richard Plomin, investigated the cognitive abilities of nearly 15,000 pairs of British twins (both monozygotic and dizygotic) at the ages of 2, 3, 4, 7, 9, 10, 12, 14, 16, 18 and 21 in order to gain understanding of the relationship between IQ and genes. The aggregation of single-nucleotide polymorphisms (DNA sequence variations often referred to as SNPs) in genome wide association studies concluded that inherited differences in SNPs accounts for approximately 50% of an individual’s intelligence. Each SNP has very little effect on IQ, only increasing or decreasing IQ by an average of 0.005%, and so 10,000 of them must be aggregated to equal the 50%. Genome Wide association studies can be used similarly to link gene variants with around 2,000 other traits including likeliness to have heart failure, depression and diabetes. 

A year ago, no specific gene had been associated with performance on an IQ test, however since then an experiment directed by Danielle Posthuma in Amsterdam has caused a major advancement in understanding the genetic underpinnings of intelligence. The study began in May 2017 by comparing the genotypes of 78,308 people with their IQ scores to successfully establish links with variants of 22 genes. By March 199,000 peoples’ genotypes had been investigated to identify links with over 500 genes variants.

From this research, Plomin proceeded to explain the potential to generate genetic IQ scores of infants to predict their future academic potential, and even set them into groups of similar ability, changing the education system massively.  However, this is unlikely and very controversial as the IQ predictions so far have not been very precise with Plomin himself coming across many twins who have performed both much better and worse than expected. Posthuma states how unlikely it is realistically because “We will never be able to look into someone’s DNA and say your IQ will be 120.”.

In conclusion, IQ is affected equally by genetics and environmental factors. Calculating the likeliness of developing traits, such as a high or low IQ, from gene variants is momentarily too inaccurate to act on but is an exciting prospect to investigate further in the future.

sources:

  • https://www.kcl.ac.uk/ioppn/depts/sgdp-centre/research/twinsearlydevelopmentstudy(teds).aspx
  • https://www.technologyreview.com/s/610339/dna-tests-for-iq-are-coming-but-it-might-not-be-smart-to-take-one/
  • https://www.nature.com/articles/nrg.2017.104.epdf?referrer_access_token=TpmBb9w5DmYbL0VYuSCqStRgN0jAjWel9jnR3ZoTv0PkVtiAvh55KM2rQWkSJWLRkkxao8puND2Er8uFF3y2mPqm98JjW8kcZqvrNYKUPYE2p_wem-nkcrZORQbyyzTPMIvm0BrEpBE_A4Q21rPMjGfrAt7-k_HYC9wqRJrHhf85lRgZhWECJ4-Kr_FKKCJkGeuCOvgywX3dpuKVcdzwSAOgPa8ZF55yiw9Qx0AwAz9Fd3EewMTKOhJafvZY1L4nbOYs2tdOvuGD65416CoDndQHhDqMceB3elZM7YUs4Gk%3D&tracking_referrer=www.technologyreview.com
  • https://www.vu.nl/en/news-agenda/news/2017/apr-jun/scientists-find-new-genetic-roots-for-intelligence.aspx

 

Hello world!

Hi, I’m Hannah. I’m sixteen and am studying chemistry, biology and religious studies in the hope that I will become a medic in the future. I have created this blog to document areas of medicine which I am particularly  interested in or enthusiastic about, as well as direct experiences I have from work experience, volunteering and wider reading. I  am also keen to read blogs from other aspiring medics, medical students, junior doctors and more senior medics.  I trust that this will help me gain a greater insight into the life of a medic and, ultimately, to earn a place in medical school.

Although I am not fixated upon a specific speciality in medicine, I find myself more curious about surgery. The multitude of controversial ethical issues in medicine also interests me, for example the political and moral correctness of euthanasia, stem cell research and abortion.

Hannah Young.