Home > News > Keratin-17 promotes p27KIP1 nuclear export and degradation and offers potential prognostic utility

Keratin-17 promotes p27KIP1 nuclear export and degradation and offers potential prognostic utility

Keratins that are overexpressed selectively in human carcinomas may offer diagnostic and prognostic utility. In this study, we show how high expression of keratin-17 (K17) predicts poor outcome in cervical cancer patients, at early or late stages of disease, surpassing in accuracy either tumor staging or loss of p27KIP1 as a negative prognostic marker in this setting. We investigated the mechanistic basis for the biological impact of K17 through loss and gain of function experiments in human cervix, breast and pancreatic cancer cells. Specifically, we determined that K17 functions as an oncoprotein by regulating the subcellular localization and degradation of p27KIP1. We found that K17 was released from intermediate filaments and translocated into the nucleus via a nuclear localization signal (NLS), specific among keratins, where it bound p27KIP1 during G1 phase of the cell cycle. p27KIP1 lacks a nuclear export signal (NES) and requires an adaptor for CRM1 binding for nuclear export. In K17 we defined and validated a leucine-rich NES that mediated CRM1 binding for export. Cervical cancer cells expressing K17 mutations in its NLS or NES signals exhibited an increase in levels of nuclear p27KIP1, whereas cells expressing wild-type K17 exhibited a depletion in total endogenous p27KIP1. In clinical specimens of cervical cancer, we confirmed that the expression of K17 and p27KIP1 were inversely correlated, both across tumors and within individual tumors. Overall, our findings establish that K17 functions specially among keratins as an oncoprotein, by controlling the ability of p27KIP1 to influence cervical cancer pathogenesis.

Does caffeine fight cancer?

Epidemiological studies have shown that caffeinated drinks may help prevent skin cancer by inhibiting a DNA repair pathway, thus killing potentially precancerous cells. In English, it means that drinking drinks containing caffeine will reduce one’s chances of developing some types of cancer, including UV-associated skin cancer. That just proves that caffeine fight cancer. The results, published in the Proceedings of the National Academy of Sciences, lend support to the idea that caffeine could be added to sunblock to increase its protective effects. At the cellular level, they’re showing that caffeine is working in this way of inducing an apoptotic mechanism. This statement was then made by cancer epidemiologist Joanne Kotsopoulos of the University of Toronto.

In the 2007, a study stated that woman who drank caffeinated coffee on a daily basis had a 10 percent lower risk of nonmelanoma skin cancer. Six or more cups of coffee a day translated to a 30 percent reduction in risk. Mouse studies have also confirmed the link, with both ingested and topically-applied caffeine lowering skin cancer rates in the animals. But exactly how the stimulant protected against cancer remained mysterious. One possibility is the drug’s inhibition of ataxia telangiectasia and Rad3-related (ATR), a large protein kinase that senses incomplete DNA replication often a result of DNA damage and signals the cell to not divide. By inhibiting ATR activity, caffeine could make cells more likely to die in response to UV damage, preventing damaged cells from ever becoming cancerous.

Studies have shown that the caffeine molecule acts as a sunscreen. It therefore blocks the penetration of UV rays. And that is why today we see many sunblocks with a good amount of caffeine in them.

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Can sugar consumption cause breast cancer?

A recent study stated that drinking three sugar sweetened drinks a week would increase the risk of having breast cancer. The study had 776 pre-menopausal women and 779 post-menopausal women. Each women’s breast density was assessed by examining their mammograms. The women were told to make a note of sweet they consumed such as chocolates, cakes, ice cream or any sweet drinks. Also they were asked to make a note of how much of spoonful of sugar they add to the drinks.

It was then found out that post-menopausal women who consumed more of sugar, an increase in the density of breast. While the pre-menopausal women observed an increase in breast density when they consumed sugar food. These women, in a week were just consuming three sugar sweetened drinks. The study then further stated that sugar tends to increase the migration of breast cells together. This explains the fact that the premenopausal women who consumed sugar-sweetened drinks were 3 percent more likely to have dense breasts than those who didn’t consume the drinks. And having dense breasts increases your risk of breast cancer by making it difficult to see tumors on mammograms.

However, there is more to be studied on this matter. But until then there is still a link between the sugar consumption and breast density. About 40% of women in the US have dense breast and they are totally unaware of it. Doctors say that women with a dense breast are five time more likely to have a breast cancer and 10 times more likely to miss the tumor in the mammogram test.

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