Cancer is caused by
Cancer is caused by changes in the DNA of our genome. These changes can sometimes affect how our genes work. If the change happens in the wrong gene (called an oncogene), then you might get cancer.
These changes can be caused by UV light from the sun or chemicals in the environment. Sometimes our cells cause changes in our own DNA on accident. This can happen whenever a cell copies its DNA and divides.
Luckily our cells have ways to protect against DNA damage. Most of the time a cell can repair the damage. And if it can’t, then the cell commits suicide (called apoptosis). This helps prevent damaged cells from multiplying and possibly leading to cancer.
Some forms of E6 and E7 keep these damaged cells from committing suicide. So these cells keep building up mutations until they grow uncontrollably and will not die. This is the definition of a cancer cell.
Cancers can be caused by DNA mutations (gene defects) that turn on oncogenes or turn off tumor suppressor genes. … Most women with HPV don’t get cervical cancer, and certain other risk factors, like smoking and HIV infection, influence which women exposed to HPV are more likely to develop cervical cancer.
Do we know what causes cervical cancer?
In recent years, scientists have made much progress toward understanding what happens in cells of the cervix when cancer develops. In addition, they have identified several risk factors that increase the odds that a woman might develop cervical cancer (see the previous section).
The development of normal human cells mostly depends on the information contained in the cells’ chromosomes. Chromosomes are large molecules of DNA. DNA is the chemical that carries the instructions for nearly everything our cells do. We usually look like our parents because they are the source of our DNA. However, DNA affects more than the way we look.
Some genes (packets of our DNA) have instructions for controlling when our cells grow and divide. Certain genes that promote cell division are called oncogenes. Others that slow down cell division or cause cells to die at the right time are called tumor suppressor genes. Cancers can be caused by DNA mutations (gene defects) that turn on oncogenes or turn off tumor suppressor genes.
HPV causes the production of 2 proteins known as E6 and E7 which turn off some tumor suppressor genes. This may allow the cervical lining cells to grow too much and to develop changes in additional genes, which in some cases will lead to cancer.
But HPV does not completely explain what causes cervical cancer. Most women with HPV don’t get cervical cancer, and certain other risk factors, like smoking and HIV infection, influence which women exposed to HPV are more likely to develop cervical cancer.
Not all HPV is Created Equal
HPV is the most common sexually transmitted infection. About 75-80% of people will get HPV before the age of 50 and over 20 million women in the U.S. alone are infected. Luckily though, most of these cases won’t go on to cause the cancer.
See, there are tons of HPVs and not all of them cause cervical cancer. In fact, most people with HPV do not develop any symptoms or health problems at all. In 90% of cases, the body’s immune system fights off HPV naturally within two years.
Sometimes though, the virus can survive in a woman for years. If it can do so for 15 or 20 years, then it can sometimes convert normal cells on the surface of the cervix into cancerous ones.
This is why some types of HPV viruses are called high-risk, oncogenic, or carcinogenic. These include HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 56, 58, 59, 66, 68, and 73. That’s a whole lot of numbers. What’s the different between these and the low-risk group?
The answer is in the HPV genome. A genome is almost always made of DNA and contains all the genetic information necessary to make a living thing. So a viral genome contains all the instructions needed to make new viruses.
Just like individual people can have slightly different genomes, so too can different HPVs. In virology, these different types are called strains.
A viral genome is much simpler than a human one. A virus really just needs to make copies of itself that can go on to infect more people. This takes very few instructions.
The genome of an HPV has six early (E) genes that help control the virus genes and how they behave in cells. They also have two late (L) genes with the instructions for the shell of the virus. And part of the genome helps control when these various genes are turned on as well.
The two most important HPV genes in the development of cancer are E6 and E7. Both of these genes need to be on all the time in order for cancer to develop.
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