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CONTENTS, ENGLISH, General, GENETICS

Cancer for beginners: all you need to know

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Cancer is one of the main causes of die in humans. It is estimated that one of two men and one of three women will suffer cancer during their life. We listen to discuss cancer or we know somebody who has cancer, but do we know what cancer is? Then, I explain it.

WHAT IS CANCER?

A malignancy is a tumour. Not all tumours are malignant, there are benign tumours too. A benign tumour does not invade surrounding tissue, while a malignant tumour does it. When a tumour is malignant we call it cancer. If a malignant tumour advances to another tissue it can metastasize, but not all malignant tumours spread.

Cancer can be defined as a group of diseases because it is considered that each one is a different illness. This group of diseases is characterised by an uncontrollably proliferation of cells, caused by genetic mutations. So, cancer is a genetic basis disease. It does not involve that it is also inherited, only 5-10% of cancers is inherited.

Cells have three main pathways where they decide if to live or to die, to divide or not divide and to differentiate or not differentiate. When some of this pathways is broken cancer is produced. There is an abnormal growth where it should not be (Figure 1). It results to interrupt the mechanisms of regulation that govern the normal cellular behaviour.

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Figure 1. Evolution of cancer. Firstly, randomly, one cell suffers a genetic mutation. Then, there is a growth of these cancer cells, producing a benign tumor. When this mass advances to another tissue is called malign tumor, and it can metastasize (Source: Cancer Genomics)

TYPES OF CANCER

There are two types of cancer: haematological cancer and solid cancer. Haematological cancers are involved with blood and lymph (leukaemia and lymphoma), while solid cancers are the rest. Inside the group of solid cancer, the most frequents are carcinomas (epithelial tissue) and sarcomas (connective tissue: muscle, bone, fat).

The majority of cancers are carcinomas because epithelial tissue are in constant regeneration and cellular division. This tissue covers or defines the surface of organs, cavities and tubes. Another reason is this tissue is more exposed to carcinogens.

CAUSES OF CANCER

Genetic mutations, which cause cancer, can be produced by external or environmental factors or by internal or intrinsic factors.

In external factors we find physical agents (radiation), chemical agents (diet, tobacco) or biological agents (virus or bacteria). Instead, internal factors can be produced by reparation errors, where random is important. Reparation errors refer to cell’s mechanisms to correct its faults when it replicates. Sometimes, if a mistake occurs, the cell is able to correct it. However, it can always occur that mistake is not repaired that by the likelihood is normal that happens.

Genetic predisposition has to be taken into account because to inherit a mutated gene (inherited cancer) or to have a polymorphism can be done susceptibility to cancer. In the last case, environment is very important.

CAN WE PREVENT CANCER?

Every year around 450,000 people are diagnosed with cancer. This figure refers to incidence, which means the number of new cases for a year. Do not confuse with prevalence, which is the total number of cases (Figure 2). The experts estimate that more than 4 of 10 cases can be prevented, if people change their lifestyle.

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Figure 2. Representative picture of incidence, prevalence and deaths. Incidence is the new cases in a certain period. However, prevalence is total cases (people with cancer or people being completely healed from cancer) (Source: Epi-demio-logy, modified)

Prevention is the set of actions which have the aim of:

  • Reduce incidence: around a 40% of cancers can be avoided with healthy lifestyle habits.
  • Reduce mortality: to detect a cancer in its early stage and to apply treatments more specifics.

We have to be taken into account that healthy living is not a guarantee against cancer. For example, we know that it’s possible for a heavy smoker to live a cancer-free life, while someone who never touches cigarettes could develop lung cancer. But lots of large long-term studies clearly show that people who have never smoked are far less likely to develop or die from cancer than smokers.

12 TIPS TO PREVENT CANCER

Prevention is important because it stacks the odds in your favour, by reducing the risk of developing the disease.

If you initiate healthy lifestyle habits and follow these tips (Figure 3), they can help you to prevent cancer:

  1. Do not smoke: one of three cancers is related to tobacco.
  2. Make your home smoke free: avoid tobacco smoke at workplace too.
  3. Take action to be a healthy body weight: you will also reduce your risk in many other diseases.
  4. Be physically active in everyday life: minimum 30 minutes of moderate intensity.
  5. Have a healthy diet: eat plenty of whole grains, pulses, vegetables and fruits and limit red meat and foods high in salt.
  6. If you drink alcohol of any type, limit your intake: not drinking alcohol is better for cancer prevention.
  7. Avoid too much sun: use sun protection and do not use sunbeds.
  8. Protect yourself against cancer-causing substances by following health and safety instructions, in the workplace.
  9. Take action to reduce high radon levels: find out if you are exposed to radiation from naturally high radon levels in your home.
  10. For women: breastfeeding reduces the mother’s cancer risk. So, if you can, breastfeed your baby. And hormone replacement therapy (HRT) increases the risk of certain cancers. Limit use of HRT.
  11. Vaccination: ensure your children take part in vaccination programmes for hepatitis B (for newborns) and human papillomavirus (HPV) (for girls).
  12. Take part in organised cancer screening programmes for bowel cancer (men and women), breast cancer (women) and cervical cancer (women).
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Figure 3. Tips of healthy habits to prevent cancer (Source: Codi Europeu Contra el Càncer)

REFERENCES

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CONTENTS, ENGLISH, General, GENETICS

Nutritional genomics: À la carte menu

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When Hipprocrates said “let food be your medicine and medicine be your food” he knew that food influences our health. And it tells us that nutritional genomics, which I will discuss in this article; a new science appeared in the post genomic era as a result of the sequencing of human genome (all DNA sequences that characterize an individual) and the technological advances that allow the analysis of large amounts of complex information.   

WHAT IS NUTRITIONAL GENOMICS?

The aim of nutritional genomics is to study the interactions of genes with elements of the human diet, altering cellular metabolism and generating changes in the metabolic profiles that may be associated with susceptibility and risk of developing diseases.

This study wants to improve the health and to prevent diseases based on changes in nutrition. It is very important not understand nutritional genomics how that specific food or nutrients cause a particular answer to certain genes.

When we talk about diet we have to distinguish between what are nutrients and what are food. Nutrients are compounds that form part of our body, while foods are what we eat. Food can take many nutrients or only one (such as salt).

NUTRIGENOMICS vs. NUTRIGENETICS

Within nutritional genomics we find nutrigenomics and nutrigenetics, but although their names we may seem to mean the same is not the case (Figure 1).

Nutrigenomics is the study of how foods affect our genes, and nutrigenetics is the study of how individual genetic differences can affect the way we respond to nutrients in the foods we eat.

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Figure 1. Schematic representation of the difference between nutrigenomics and nutrigenetics (Source: Mireia Ramos, All You Need is Biology)

NUTRIGENOMICS IN DETAIL

Nutrients can affect metabolic pathways and homeostasis (balance) of our body. If this balance is disturbed chronic diseases or cancer may appear, but it can also happen that a disease, which we have it, be more or less severe. It means that impaired balance can give the appearance, progression or severity of diseases.

The aim of nutrigenomics is that homeostasis is not broken and to discover the optimal diet within a range of nutritional alternatives.

Thus, it avoids alterations in genome, in epigenome and/or in expression of genes.

ALTERATIONS IN GENOME

Free radicals are subproducts that oxidise lipids, proteins or DNA. These can be generated in mitochondria, organelles that we have inside cells and produce energy; but we can also incorporate from external agents (tobacco, alcohol, food, chemicals, radiation).

In adequate amounts they provide us benefits, but too much free radicals are toxic (they can cause death of our cells).

Antioxidants neutralize free radicals. But where can we get these antioxidants? There are foods that contain them, as Table 1 shows.

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Table 1. Example of antioxidants and some foods where we can find them (Source: ZonaDiet)

The way we cook food or cooking is important for avoid to generate free radicals. In barbecues, when we put the meat on high heat, fats and meat juices fall causing fire flames. This produces more flame and it generates PAHs (a type of free radicals). These adhere to the surface of the meat and when we eat it can damage our DNA.

ALTERATIONS IN EPIGENOME

Epigenome is the global epigenetic information of an organism, ie, changes in gene expression that are inheritable, but they are not due to a change in DNA sequence.

Epigenetic changes may depend on diet, aging or drugs. These changes would not have to exist lead to diseases as cancer, autoimmune diseases, diabetes…

For example, with hypomethylation, in general, cytosines would have to be methylated are not. What does it mean? Hypomethylation silenced genes and then, they cannot be expressed. Therefore, we need methylated DNA. A way of methylate DNA is eating food rich in folic acid.

ALTERATIONS IN GENE EXPRESSION

There are agents (UV rays) that activate pathways that affect gene expression. Occurring a cascade that activates genes related to cell proliferation, no differentiation of cells and that cells survive when they should die. All this will lead us cancer.

It has been found that there are foods which, by its components, can counteract activation of these pathways, preventing signal transduction is given. For example curcumin (curry), EGCG (green tea) or resveratrol (red wine).

 REFERENCES

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