Navigation Links
Slow growth of childhood brain tumors linked to genetic process seen in skin moles
Date:6/23/2011

Johns Hopkins researchers have found a likely explanation for the slow growth of the most common childhood brain tumor, pilocytic astrocytoma. Using tests on a new cell-based model of the tumor, they concluded that the initial process of tumor formation switches on a growth-braking tumor-suppressor gene, in a process similar to that seen in skin moles.

The findings, published in the June 1 issue of Clinical Cancer Research, could lead to better ways of evaluating and treating pilocytic astrocytomas.

"These tumors are slow-growing to start with, and sometimes stop growing, and now we have a pretty good idea of why that happens," says Charles G. Eberhart, M.D., Ph.D., associate professor of Pathology, Ophthalmology and Oncology at Johns Hopkins. "These tumors also can suddenly become more aggressive, which we now think represents an inactivation of this tumor-suppressor gene, and this inactivity could be used as a marker to determine which patients need more therapy."

Pilocytic astrocytoma arises in brain cells known as astrocytes, which, among many functions in the brain, help support neurons. These cancerous astrocytes have DNA mutations that force a growth-related gene, BRAF, into an abnormal, always-on state. Biologists call such cancer-driving genes oncogenes.

Eberhart and his team used a viral gene-transfer technique to deliver an oncogenic, always-on version of BRAF, to fetal brain cells in a lab dish. The idea was to create a cell model of pilocytic astrocytoma, to enable easier study of its growth patterns. As the researchers expected, the cells quickly formed tumorlike colonies but the growth of these colonies soon sputtered out.

The same phenomenon, sparked by an oncogene, was first described six years ago in a study of the biology of skin moles. Moles typically begin in skin cells whose inherited or spontaneous mutations often affecting BRAF drive the cells' growth beyond normal limits. "The oncogene drives the excessive growth of skin cells, which forms a mole. This overgrowth triggers the downstream activation of tumor-suppressor genes, which stops the mole from growing further," says Eberhart.

In the current study, Eberhart and his colleagues found evidence that this same process, which is called oncogene-induced senescence, also occurs in pilocytic astrocytoma and minimizes its spread. As their tumor-model cells became senescent, the activity of p16, a well-known tumor-suppressor gene, increased and acted as a brake to stop further tumor growth.

Next, the researchers checked pilocytic astrocytoma samples from 66 patients, using a tissue registry at the Johns Hopkins Department of Pathology. Most (57 of 66) showed signs of p16 tumor-suppressor activity, and the remaining nine samples had no signs of p16 activity. Of the p16-active tumors, only two samples (3.6 percent) were from patients who had died of their cancer; however, three of the nine samples with inactive p16 (33 percent) were from patients who had died.

"Our hypothesis now is that these tumors become fast-growing and aggressive again when they can somehow find a way to shut off p16 and escape senescence," says Eric Raabe, M.D., Ph.D., fellow in pediatric oncology at Johns Hopkins. "In many cases, a single tumor may contain some cells that are senescent plus others that have escaped senescence and started proliferating again," he added.

In future work, Eberhart says, he and his colleagues will examine whether a new class of BRAF-inhibiting cancer drugs has the unintended side effect of shutting down p16. "Clinical trials of these BRAF inhibitors are now just starting in the U.S. and Europe," he says. "We think it's important to determine whether these drugs end up affecting the process of oncogene-induced senescence."


'/>"/>

Contact: Vanessa Wasta
wasta@jhmi.edu
410-955-1287
Johns Hopkins Medical Institutions
Source:Eurekalert

Related medicine news :

1. Scientists image beginning stages of ovarian cancer growth with time-lapse technique
2. Cancer cells accelerate aging and inflammation in the body to drive tumor growth
3. Common transplant drug inhibits breast cancer growth, UNC laboratory study shows
4. Enzyme may drive breast cancer growth
5. Artificial tissue promotes skin growth in wounds
6. Obstructive sleep apnea linked to cancer growth in mice
7. Rapid growth may be appropriate trigger for treatment in patients with renal masses
8. Increases in peripheral arterial disease revascularization correlates with screening growth
9. Extra Sleep in Infants Seems to Signal Growth Spurts
10. Study is the first to link sleep duration to infant growth spurts
11. In time for spring, biologist illuminates how seedlings regulate growth
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/27/2016)... KS (PRWEB) , ... June 27, 2016 , ... TopConsumerReviews.com ... retailers of Eyeglasses . , Millions of individuals in the United States and ... have become a way to both correct vision and make a fashion statement. Even ...
(Date:6/26/2016)... ... ... legally blind and certified personal trainer is helping to develop a weight loss fitness plan ... fix the two major problems leading the fitness industry today:, , ... They don’t eliminate all the reasons people quit their exercise program ...
(Date:6/25/2016)... Viejo, California (PRWEB) , ... June 25, 2016 , ... ... to fit their specific project," said Christina Austin - CEO of Pixel Film Studios. ... fully customizable and all within Final Cut Pro X . Simply select a ...
(Date:6/25/2016)... ... June 25, 2016 , ... Conventional wisdom preaches the benefits of ... of the latter, setting the bar too high can result in disappointment, perhaps even ... progress toward their goal. , Research from PsychTests.com reveals that behind ...
(Date:6/24/2016)... ... June 24, 2016 , ... ... Scientific Sessions in Dallas that it will receive two significant new grants to ... came as PHA marked its 25th anniversary by recognizing patients, medical professionals and ...
Breaking Medicine News(10 mins):
(Date:6/24/2016)... , June 24, 2016 According ... by Type (Standard Pen Needles, Safety Pen Needles), Needle ... GLP-1, Growth Hormone), Mode of Purchase (Retail, Non-Retail) - ... This report studies the market for the forecast period ... reach USD 2.81 Billion by 2021 from USD 1.65 ...
(Date:6/23/2016)... HOUSTON , June 23, 2016  MedSource ... platform as its e-clinical software solution of choice.  ... the best possible value to their clients by ... nowEDC.  The preferred relationship establishes nowEDC as the ... pricing for MedSource,s full-service clients.  "nowEDC has long ...
(Date:6/23/2016)... 2016  In a startling report released today, National Safety ... lacking a comprehensive, proven plan to eliminate prescription opioid overdoses. ... how states are tackling the worst drug crisis in recorded U.S. ... Kentucky , New Mexico , ... Of the 28 failing states, three – Michigan ...
Breaking Medicine Technology: