Featured Research

from universities, journals, and other organizations

Melanoma: The wolf in sheep’s clothing

Date:
October 10, 2012
Source:
Universität Bonn
Summary:
Melanoma is so dangerous because it tends to metastasize early on. New treatment approaches utilize, among other things, the ability of the immune defense to search out and destroy malignant cells. Yet this strategy is often only temporarily effective. A research team has discovered why this is the case: In the inflammatory reaction caused by the treatment, the tumor cells temporarily alter their external characteristics and thus become invisible to defense cells. This knowledge forms an important foundation for the improvement of combination therapies.

Prof. Thomas Tüting.
Credit: Claudia Siebenhüner/UKB

Melanoma is so dangerous because it tends to metastasize early on. New treatment approaches utilize, among other things, the ability of the immune defense to search out and destroy malignant cells. Yet this strategy is often only temporarily effective. A research team under the direction of Bonn University has discovered why this is the case: In the inflammatory reaction caused by the treatment, the tumor cells temporarily alter their external characteristics and thus become invisible to defense cells. This knowledge forms an important foundation for the improvement of combination therapies.

The results have been published online in the journal Nature.

In Germany, approximately 15,000 people develop melanoma annually and approximately 2,000 people die from it every year. Malignant melanoma is the most frequently fatal skin diseases. The particular malignancy is based on the fact that small tumors can spread via the lymphatic vessels and the bloodstream. For many years, the working group under Prof. Dr. Thomas Tüting, Director of the Laboratory for Experimental Dermatology at the Bonn University Hospital, has investigated the effect of a targeted immune therapy with tumor-specific defense cells.

Tumor cells behave like a wolf in sheep's clothing

In trials on mice who congenitally develop melanoma, the researchers were able to destroy advanced tumors using so-called cytotoxic T-cells. "But they recover after some time -- just as they do in patients in the hospital," explain Dr. Jennifer Landsberg and Dr. Judith Kohlmeyer, lead authors of the study. This form of therapy triggers inflammation. Now the researchers have discovered that the melanoma cells change their external characteristics precisely via this accompanying inflammatory reaction. "They behave like wolves in sheep's clothing and thus evade detection and destruction by defense cells," says Marcel Renn, also a lead author of the study.

The immune system can fight tumors -- but it can also protect them

On the search for the underlying mechanisms, the researchers pointed histological investigations of tumors in the right direction: Therapy-resistant melanomas demonstrated a significantly stronger inflammatory reaction with many scavenger cells of the immune system, the so-called macrophages. A messenger primarily released from these immune cells -- the tumor necrosis factor-alpha -- was able to bring about the change in character of the melanoma cells directly in the Petri dish in the laboratory. Cells treated in this way were subsequently hardly detected by the defense cells. "The immune system is like a double-edged sword," explains Prof. Tüting. "It can fight the tumor -- but it can also protect it." Such changes in the tumor tissue are probably of great importance for the formation of resistance to therapy. "According to more recent discoveries, treatment with inhibitors which prevent signal transmission in tumor cells is also affected by this," remarks Prof. Tüting.

Melanoma cells lose their typical characteristics

Molecular genetic investigations revealed that melanoma cells from therapy-resistant tumors had lost the characteristics typical for pigment cells. Instead, they demonstrated traits of connective tissue cells. "It is possible that melanoma cells undergo this change in character so easily because they originate from the embryonic development of cells in the neural crest which can also form connective tissue and nerve cells," says Prof. Dr. Michael Hölzel, co-author from the Institute for Clinical Pharmacology and Clinical Chemistry at the Bonn University Hospital.

Results can also be transferred to humans

Findings initially gained from laboratory mice were also able to be reproduced by the team of researchers with human melanoma cells and various associated defense cells in the Petri dish. The melanoma cells likewise reacted to the messenger tumor necrosis factor-alpha with a loss of pigment cell characteristics and could then no longer be detected by pigment-cell-specific defense cells. "Detection by other defense cells which can search out specific genetic changes in the melanoma cells was not affected by this, however," stresses Prof. Dr. Thomas Wölfel, director of a working group involved in the study at the Medical Clinic III of the Mainz University Hospital.

Important findings for new treatment strategies

As soon as the tumor necrosis factor alpha no longer had an effect on the human and mouse melanoma cells, however, the cells regained their pigment-cell characteristics. Then they were also able to be detected and fought against by all immune defense cells once more. All of these findings yield important information for new treatment strategies. Thus in the future, defense cells against antigens of various categories and specificity should be used and at the same time, the inflammation utilized by the tumor cells should be therapeutically inhibited. "Our experimental model system will help us to develop optimally effective combination therapies as rapidly as possible," says Prof. Tüting. "However, it will still take several years until the clinical application of strategies of this type."


Story Source:

The above story is based on materials provided by Universität Bonn. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jennifer Landsberg, Judith Kohlmeyer, Marcel Renn, Tobias Bald, Meri Rogava, Mira Cron, Martina Fatho, Volker Lennerz, Thomas Wölfel, Michael Hölzel, Thomas Tüting. Melanomas resist T-cell therapy through inflammation-induced reversible dedifferentiation. Nature, 2012; DOI: 10.1038/nature11538

Cite This Page:

Universität Bonn. "Melanoma: The wolf in sheep’s clothing." ScienceDaily. ScienceDaily, 10 October 2012. <www.sciencedaily.com/releases/2012/10/121010141104.htm>.
Universität Bonn. (2012, October 10). Melanoma: The wolf in sheep’s clothing. ScienceDaily. Retrieved October 20, 2014 from www.sciencedaily.com/releases/2012/10/121010141104.htm
Universität Bonn. "Melanoma: The wolf in sheep’s clothing." ScienceDaily. www.sciencedaily.com/releases/2012/10/121010141104.htm (accessed October 20, 2014).

Share This



More Health & Medicine News

Monday, October 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How Nigeria Beat Its Ebola Outbreak

How Nigeria Beat Its Ebola Outbreak

Newsy (Oct. 20, 2014) — The World Health Organization has declared Nigeria free of Ebola. Health experts credit a bit of luck and the government's initial response. Video provided by Newsy
Powered by NewsLook.com
Another Study Suggests Viagra Is Good For The Heart

Another Study Suggests Viagra Is Good For The Heart

Newsy (Oct. 20, 2014) — An ingredient in erectile-dysfunction medications such as Viagra could improve heart function. Perhaps not surprising, given Viagra's history. Video provided by Newsy
Powered by NewsLook.com
Ebola Worries End for Dozens on U.S. Watch Lists

Ebola Worries End for Dozens on U.S. Watch Lists

Reuters - US Online Video (Oct. 20, 2014) — Forty-three people who had contact with Thomas Eric Duncan, the first person diagnosed with Ebola in the U.S., were cleared overnight of twice-daily monitoring after 21 days of showing no symptoms. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Fauci: Ebola Protocols to Focus on Training

Fauci: Ebola Protocols to Focus on Training

AP (Oct. 20, 2014) — Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, says he expects revised CDC protocols on Ebola to focus on training, observation and ensuring health care workers are more protected. (Oct. 20) Video provided by AP
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:

Strange & Offbeat Stories

 

Health & Medicine

Mind & Brain

Living & Well

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