Background:
Everyone loves a nice warm cup of tea when they are sick or feeling worn out. Throughout the years tea has seemed to have a soothing effect on people and has become associated with making people recover faster from the cold or flu. But what if tea is way more important than that; what if tea could keep you from getting cancer!? According to Lambert and Chung, there is a component in green tea called catechins that may aid in many cancer preventive functions such as inhibiting growth factor signaling, promoting apoptosis, and inhibiting protein kinases from functioning. Catechins are defined as a polyphenol compound from the plant Camellia sinensis and have been thought to have antioxidant properties. I am aiming to analyze this claim and get a better idea about how much of a preventative effect tea really has.
Mechanisms of Prevention:
Lambert and Chung have proposed several mechanisms on how the catechins can intervene with cancer pathways. The first is by inhibiting the MAP kinase signaling pathway by interfering with the phosphorylation of integral proteins and therefore preventing Raf-1 from associating with MEK-1. This was shown in a mouse model by injecting 20 umol/L of a catechin called epigallocatechin gallate(EGCG) and they saw a minimal decrease in the association of Raf and Mek after 15 minutes.
http://www.jnsbm.org/viewimage.asp?img=JNatScBiolMed_2014_5_1_3_127272_u1.jpg
The second mechanism proposed is inhibition of the excessive growth factor signaling in cancer cells and also induction of apoptosis. Researchers have shown that there is a correlation between EGCG and a 58% decrease in tumor growth in colon cancer cells grown in vitro. They also showed a 1.9 fold increase in apoptosis.This works by inhibiting the phosphorylation of many important proteins and therefore causing cell death. For these cell growth inhibiting mechanisms to be seen experimentally, 30 umol/L of EGCG were needed.
Analysis:
After reading this article in support of tea and its main preventative component EGCG, I was not thoroughly convinced that tea was the answer to cancer. There arguments seemed to be very weakly supported and lacked a plethora of experimental data to corroborate the findings. When I looked for other articles that made similar claims to Lambert and Chung, I found very mixed reviews on the impact of tea. Numerous researchers made the claim that significant results have not yet been documented regarding the overall effects that tea has in humans.
The table above is from a study done to test the effects of green tea(EGCG), curcumin, or combined on cancer cell proliferation, apoptosis, and angiogenesis. This study was also done on rats and no study in humans has been successful at showing a consistent correlation of EGCG and decreased risk of any cancer type. However, this graph does show that in squamous cell carcinoma of rats, the apoptotic index increased most for green tea and green tea+curcumin. The proliferative index decreased the most for green tea+curcumin, and the angiogenesis also decreased most for green tea+curcumin. These results lead me to believe that maybe the answer to cancer prevention does not lie in just one compound, but in the synergistic effects of multiple compounds administered together. I think that for the future, studies could be done on the effects of combining compounds thought to prevent cancer to see which ones react well or poorly. This could amplify the tumor suppressing mechanisms and be much more cost efficient prevention than the current drugs available. I am also curious about the dosage that would be given in humans and if there would be any detrimental side effects from the utilization of compounds like EGCG. After doing all of the research on the correlation of tea and cancer, I think it is too soon to tell whether or not their is a significant impact of catechins on human cancer. I do, however, think there is some incentive to pursue researching the idea of catechin prevention and better understanding the mechanisms employed against cancer cell lines.
Sources:
Lambert, Joshua, and Chung Yang. "Mechanisms of Cancer Prevention by Tea Constituents."The Journal of Nutrition (2003)133: n. pag. Web. 14 May 2014.
Ni, Ling. "Inhibition of 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral carcinogenesis in hamsters by tea and curcumin." Carcinogenesis 23: 1307-1313. Web. 14 May 2014. (chart)
