Featured Research

from universities, journals, and other organizations

Arsenic And Old Telomerase: Hopkins Researchers Unravel Effects Of Arsenic On Human Cells

Date:
November 15, 2001
Source:
Johns Hopkins Medical Institutions
Summary:
Researchers at Johns Hopkins report discovering a mechanism that may account for the paradoxical effects of arsenic, which is both a treatment for cancer and a carcinogen.

Researchers at Johns Hopkins report discovering a mechanism that may account for the paradoxical effects of arsenic, which is both a treatment for cancer and a carcinogen.

Once a crucial element in the medical repertoire of Hippocrates for successfully treating infections like malaria, syphilis and yaws, arsenic is also an effective treatment for certain types of leukemia, or cancer of white blood cells. Long-term exposure to arsenic in drinking water, however, has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver and prostate.

"Arsenic has dual effects depending on the background; in normal cells it can cause cancer, and in cancerous cells it can lead to cell death. We have found one mechanism that may explain both of these effects," says Chi V. Dang, M.D., professor and director of hematology at Hopkins and co-author of the paper.

Specifically, Dang and his team found that arsenic inhibits transcription of a gene, hTERT, that in turn inhibits the expression of telomerase, an enzyme that protects the ends of chromosomes. Low levels of telomerase cause end-to-end fusions of chromosomes, which promote genetic instability. This instability may then lead to cancer in healthy cells and apoptosis, or cell death, in cancerous cells, according to Dang.

The Hopkins researchers report their findings in the current issue of The Journal of Clinical Investigation.

Serendipity had much to do with the discovery, according to Dang. While investigating how cancer cells react to arsenic, one of the researchers, Wen-Chien Chou, a graduate student in human genetics and molecular biology at Hopkins, noticed that some of the cells were abnormally large and tended to die sooner than expected. They then found that these big cells also had end-to-end fusion of their chromosomes, suggesting that arsenic was somehow causing genetic instability.

"It didn't take long to put two and two together," says Dang. "Once we saw the fused chromosomes we knew that telomerase might be responsible. So we did a very direct experiment that asked: Does arsenic inhibit telomerase? The answer is absolutely yes. Cells exposed to arsenic exhibit a dramatic inhibition of telomerase."

The findings have implications for both the development of therapies for treating cancer and for larger public health issues relating to acceptable levels of arsenic in drinking water.

"We've provided evidence that arsenic causes genetic instability potentially leading to cancer," says Dang. "This provides an underlying scientific reason for why we don't want high levels of arsenic in our drinking water." The World Health Organization (WHO), the Department of Health and Human Services (DHHS), and the EPA have determined that arsenic is carcinogenic to humans.

The results could also lead to development of more effective chemotherapy to treat leukemia. Studies in China and elsewhere have shown that the compound arsenic trioxide is very effective in treating acute promyelocytic leukemia (APL), a variant of acute myeloid leukemia that accounts for 10 percent to 15 percent of this cancer in adults, according to Dang.

"Chemotherapy works by attacking a number of different weak points of a cancer cell," says Dang. "Our findings put into perspective how arsenic can be used in combination with other drugs in chemotherapy to fight cancer."

Arsenic is a naturally occurring element found throughout the earth's crust and also in water, air, plants and animals. It is released into the environment through natural geological processes such as volcanism, erosion of rocks, forest fires, and through human industrial activity.

###

The research was supported by the National Institutes of Health.

Chou, Wen-Chien, et al., Arsenic inhibition of telomerase transcription leads to genetic instability. Journal of Clinical Investigation, 2001, vol. 108, no. 10.

Related Web site:

Johns Hopkins Division of Hematology: http://www.blooddiseasehopkins.org/


Story Source:

The above story is based on materials provided by Johns Hopkins Medical Institutions. Note: Materials may be edited for content and length.


Cite This Page:

Johns Hopkins Medical Institutions. "Arsenic And Old Telomerase: Hopkins Researchers Unravel Effects Of Arsenic On Human Cells." ScienceDaily. ScienceDaily, 15 November 2001. <www.sciencedaily.com/releases/2001/11/011114070613.htm>.
Johns Hopkins Medical Institutions. (2001, November 15). Arsenic And Old Telomerase: Hopkins Researchers Unravel Effects Of Arsenic On Human Cells. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2001/11/011114070613.htm
Johns Hopkins Medical Institutions. "Arsenic And Old Telomerase: Hopkins Researchers Unravel Effects Of Arsenic On Human Cells." ScienceDaily. www.sciencedaily.com/releases/2001/11/011114070613.htm (accessed July 30, 2014).

Share This




More Health & Medicine News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Generics Eat Into Pfizer's Sales

Generics Eat Into Pfizer's Sales

Reuters - Business Video Online (July 29, 2014) Pfizer, the world's largest drug maker, cut full-year revenue forecasts because generics could cut into sales of its anti-arthritis drug, Celebrex. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins