Important how cells copy chromosomes for fighting cancer

As we find out more and more about what goes wrong inside cells, the better we become at killing cancer without harming the rest of the body. Now, scientists have discovered a key step in how cells copy their 
chromosomes when they divide that promises to be very useful for cancer research.

Karim Labib, a professor in life sciences at the University of Dundee in Scotland, and colleagues report how they solved an important mystery in cell biology in the journal Science.
Life depends on cells being able to multiply, a key part of which is copying chromosomes, the tightly packed bundles of DNA that carry the genetic blueprint of the individual.
The chromosome copying process has to copy the genetic information perfectly for new cells to grow and carry out their function normally. The more mistakes that are made, the more likely that cells will behave abnormally and triggercancer.

We do not know enough about how chromosome copying works

cancer cell
The researchers say one of the fundamental biological processes that go wrong in cancer is that the chromosome copying machinery has not worked properly. Their new study sheds light on this process.
Prof. Labib says ever since Watson and Crick first revealed the structure of DNA, scientists have been fascinated by how cells copy chromosomes, yet "we are still quite a way from having a complete picture of how it works."
He and his colleagues focused on the stage when the cells finish copying their chromosomes. Scientists already know something about this; it is vital that this happens correctly for the genetic blueprint to be passed on to the next generation of cells.
"We already knew that 11 proteins in the cell combine to build a molecular 'machine' called the DNA helicase, which plays a vital role in copying the double helix of DNA that is at the heart of each chromosome," Prof. Labib adds.
He explains that the DNA helicase unwinds the two strands of the double helix of DNA, so they can each be copied, and that:
"It is vital that the helicase is only built once during the life of each cell, and then is taken apart or disassembled once it has done its job, so that cells just make one single copy of each chromosome."

Understanding disassembly of the DNA helicase is important for cancer research

Until now, scientists did not know how the helicase disassembled. This is what the team at Dundee discovered. They found, because of a process called "ubiquitylation," one of the 11 components of the helicase falls out when chromosome copying is complete.
Because this one component falls out, the other proteins are unable to stick together, and the DNA helicase falls apart.
"It turns out that this is a very good thing," says Prof. Labib, "as genetic studies show that if the helicase does not come apart but instead remains glued to the chromosomes, then this leads to major problems."
He says this is one of the fundamental biological processes that go wrong in cancer, "almost any time that we see cancer developing, one of the things that has gone wrong early in the process is that the chromosome copying machinery has not worked properly."
The research was funded by the Medical Reseach Council, Cancer Research UK and the Wellcome Trust.
Meanwhile, in another area of cancer research, Medical News Today recently learned that researchers have found a molecule that helps cancer cells evade the immune system.

Sleeping with more than 20 women in a lifetime linked to lower prostate cancer

Around 1 in 7 men will be diagnosed with prostate cancer in their lifetime.

 But a new study - which is likely to be welcomed by many men - claims that having more than 20 female sexual partners in a lifetime may significantly reduce the risk of developing the disease. 

Sleeping with more than 20 men in a lifetime, however, is associated with increased risk of prostate cancer.

The research team, from the University of Montreal's School of Public Health in Canada, publish their findings in the journal Cancer Epidemiology.

According to the researchers, the link between sexual activity and prostate cancer risk remains
controversial. Some studies have associated high sexual activity with a greater risk of the disease,
while others have suggested the opposite.
In this study, the team set out to determine whether the number of sexual partners men have throughout their lifetime influences their risk of prostate cancer.
They analyzed 3,208 men who were part of the Prostate Cancer & Environment Study (PROtEuS) in Montreal, Canada. Of these, 1,590 were diagnosed with prostate cancer between 2005 and 2009, while the remaining 1,618 men were free of the disease.
As part of this study, all men were required to complete a questionnaire that asked about their sexual activity, as well as sociodemographic, environmental and lifestyle factors.

28% lower prostate cancer risk among men who slept with more than 20 women

The team was not surprised to find that men who had a relative with prostate cancer were twice as likely to have the disease themselves. A family history of prostate cancer is a well-established risk factor.
However, the researchers found that a man's prostate cancer risk also appeared to be influenced by the number of sexual partners he had in his lifetime.
Men who reported never having a sexual partner were twice as likely to develop prostate cancer than those who reported having sexual partners.
However, the team found that men who had slept with more than 20 women in their lives had a 28% lower risk of developing all types of prostate cancer and a 19% lower risk of developing aggressive prostate cancer, compared with those who had slept with fewer than 20 women.
"It is possible that having many female sexual partners results in a higher frequency of ejaculations, whose protective effect against prostate cancer has been previously observed in cohort studies."
The researchers explain that some studies have suggested that the more a man ejaculates, the lower the concentrations of cancer-causing substances in his prostatic fluid. Other studies have indicated that a higher frequency of ejaculations may also reduce the production of intraluminal crystalloids in the prostate, which have been linked to higher risk of cancer.
The number of sexually transmitted infections (STI) participants contracted in their lifetime did not appear to influence the risk of prostate cancer, the researchers say, noting that only 12% of men reported having at least one STI in their lives.
In addition, the team found no association between the age at which the men first had sexual intercourse and prostate cancer risk.

Men with more than 20 male sexual partners twice as likely to develop prostate cancer

It was not good news for men who had slept with more than 20 male partners in their lifetime, however.
The team found that these men were twice as likely to develop all types of prostate cancer, compared with men who had never had a sexual partner. Furthermore, men who had slept with more than 20 male partners had a 500% increased risk of developing a less aggressive prostate cancer, compared with those who had only slept with one man.
The researchers are unable to accurately identify the reasons behind these findings, but they speculate that it could be a result of higher exposure to STIs among this group. Furthermore, they note that physical trauma to the prostate may be caused by anal intercourse, which could raise the risk of prostate cancer.
Commenting on their overall results, the researchers say:
"Our findings are in support of a role for the number of sexual partners in prostate cancer development. The gender of sexual partners should be taken into account in future studies investigating this association."
Medical News Today recently reported on a study suggesting that men with a specific baldness pattern may be at higher risk of prostate cancer.
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