Home > News > An in vivo method to identify microRNA targets not predicted by computation algorithms: p21 targeting by miR-92a in cancer

An in vivo method to identify microRNA targets not predicted by computation algorithms: p21 targeting by miR-92a in cancer

microRNAs (miRNAs) dysregulation is involved in the development and progression of various human cancers, including hepatocellular carcinoma (HCC). However, how to identify the miRNAs targeting specific mRNA in cells is a significant challenge because of the interaction complexity and the limited knowledge of rules governing these processes. Some miRNAs are not predictable by current computer algorithms available. Here, using p21 mRNA as target, we established a new method, named as miRNA in vivo precipitation (miRIP), to identify which kind of miRNAs can actually bind to the specific mRNA in cells. Several unpredictable miRNAs which bound p21 mRNA in HepG2 and PC-3 cells were identified by miRIP method. Among these miRNAs identified by miRIP, miR-92a was found and confirmed to interact robustly with p21 mRNA both in HepG2 and PC-3 cells. miR-92a was found to be remarkably increased in HCC tissues, and higher expression of miR-92a significantly correlated with lower expression of p21 which is related with poor survival of HCC patients. Moreover, inhibition of miR-92a could significantly suppress HCC growth in vitro and in vivo by up-regulating p21. Together, miR-92a, which is identified by miRIP, is functionally shown to be associated with HCC growth as an oncogenic miRNA by inhibiting expression of targeting gene p21. In addition, several unpredictable miRNAs which target STAT3 mRNA were also identified by miRIP method in HepG2 cells. Our results demonstrated that miRIP approach can effectively identify the unpredictable but intracellular existing miRNAs which target specific mRNA in vivo.

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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