Be On The Lookout- Notch Pathway and DIPG

With the lag time between presentation at a meeting and publications often times things can just slip under the radar.   For me, this was certainly true of this American Association for Cancer Research abstract presented last year in Philadelphia- "High-level activation of the Notch pathway in diffuse intrinsic pontine glioma".  The title doesn't immediately excite me.  However, packed in this short abstract is a number of significant advancements in DIPG research.

1) MADC, the Mid-Atlantic DIPG Consortium, brought three geographically tied institutions together to fight DIPG.   Johns Hopkins, Children's National Medical Center and the National Institutes of Health-Pediatric Oncology Branch agreed to share DIPG tumor material that had been obtained through timely autopsy donation.

2) From a fresh tissue specimen, the researchers were able to establish a cell line- JHH-DIPG1.   The cell line was evaluated for the Notch pathway as this is known to occur in other aggressive brain tumors. JHH-DIPG1 showed a high level of  Notch pathway activation.  

3) From the cell line, a xenograft animal model was also developed.

So.... what makes this significant?  Well,

First, it is very difficult for any one institution to have enough DIPG tissue for research.   I see these type of collaborative efforts key to being able to crack the code of DIPG.

Secondly, it continues to show that parents will donate tumor after death to try to make a difference in this horrendous disease.    It shows that Stanford was not a fluke.  Cell lines and animal models can be developed for DIPG.

Thirdly, it brings DIPG more on par with other brain tumor and cancer researchers.  We now have cell lines and animal models (not only at Hopkins but also elsewhere).  Without these, research seemed at a standstill.

Finally, there are actual Notch agents that are available!  The pediatric phase 1 with the gamma-secretase inhibitor RO4929097 has already closed because it has reached its enrollment.  We are now just waiting for results.   The research here could be a basis for starting a clinical trial for DIPG with an agent- or at least being able to do more pre-clinical work with an appropriate model.   

References:
AACR Notch Abstract-
http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=5eccf257-1e78-44ad-a11d-0cb24040c222&cKey=c6e7a032-873e-4aea-a5af-1b3374b5b338&mKey=%7B2D8C569E-B72C-4E7D-AB3B-070BEC7EB280%7D

Gamma-secretase inhibitor RO4929097 in treating young patients with relapsed or refractory solid tumors, CNS tumors, lymphoma or T-Cell Leukemia
http://clinicaltrials.gov/ct2/show/NCT01088763?term=Notch+brain+tumor&rank=7

Focus On Research- Hashizume Laboratory

Rinato Hashizume, Ph.D  has been working on understanding DIPG for some time.   His lab, part of the Brain Tumor Research Center at USCF,  is specifically interested in understanding tumor molecular biology, developing animal models and using these models in novel approaches to fight pediatric brain tumors.   Here are some specific DIPG project that this lab has undertaken:

1) Diffuse Intrinsic Pontine Glioma Xenograft Panel-  One of the significant hurdles for DIPG research has been the lack of animal models to be able to preform preclinical testing for DIPGs.   This lab has established tumorigenic DIPG cell lines from human biopsy samples.  These cell have been injected into animal brainstem to create a new animal model.

2)Targeting PDGFRA- A Key Pathway for Brainstem Tumorigenesis and Effective Therpeutic Strategy-   It has been found that approximately 29-36% of DIPGs have a genetic alteration called PDGFRA amplification.  In mice, it has been found that increased PDGFR signaling of the 4th ventricle subventricular zone nestin+ cells cause gliomas.   It has also been found that the population of nestin+ cells peak about the same time as the incidence of DIPG in kids.

This labs has found that DIPG have increased PDGFRA and RB but do not have a tumor suppressor called p16NK4A.  In addition, the brainstem model was found to have both Nestin ceells and Oligo2 cells.   It is hypothesized that these cells could present a pool from where brainstem gliomas originate.  The Oligo 2 cells seem to make PDGFRA which might indicated these cells keep the gliomas growing. 

The Hashizume lab is investigating the consequences of these alternations in mice. 

3) Intranasal Delivery-  Another hurdle for DIPG treatment has been the difficulty in getting agents to the tumor because of the blood brain barrier.   This lab is working to test an alternative delivery system using the nose.   There are alot of advantages to intranasal delivery including:

-avoidance of the first pass effect of the liver on intravenous administration,

-reduction of system side effects, and 

-more convenient self administration.

This lab has shown the intranasal delivery of GRN163 has doubled survival in rats.   The lab is now working on other formulation with liposomes to try to improve on these results.

Funding for at least part of this work has come from the Pediatric Brain Tumor Foundation of the US which has been a long time supporter of the pediatric brain tumor work at UCSF through a 1.3 million dollar PBTFUS Institute Award.   This award included specific work on brainstem gliomas.

Hashizume DIPG Publications:

Telomerase inhibitors for the treatment of brain tumors and the potential of intranasal delivery.

http://www.ncbi.nlm.nih.gov/pubmed/20373260

New therapeutic approach for brain tumors:Intranasal delivery of telomerase inhibitor GRN 163.

Free Full Text-  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2613813/

An experimental xenograft mouse model of diffuse pontine glioma designed for therapeutic testing.

http://www.ncbi.nlm.nih.gov/pubmed/22231932

A human brainstem glioma xenograft model enabled for bioluminenscence imaging.

Free Full Text- http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808534/

Reference:

Hashizume Laboratory- 

http://neurosurgery.ucsf.edu/index.php/research_btrc_hashizume.html

PBTFUS Institute Program-   http://www.curethekids.org/medcomm/institutes/

Atypical "DIPGs" Not all Gliomas

This Japanese article electronically published in Childs Nervous System makes the case that although MRIs have been the basis for diagnosis for DIPGs since the 1990s,  "the accuracy of MR imaging baded diagnosis has not been fully confirmed".  This article goes on to say that there have been several reports indicating that some of these diffuse intrinsic brainstem lesions have been found to be other tumors rather than gliomas.  These have included  PNETs, ependymomas, gagliogliomas, rhabdoid tumors and pilocytic astroctyomas.   These other pathologies have been particularly found in those tumors that have an atypical appearance.

The authors decided to perform biopsy for pediatric intrinsic pontine lesions with atypical for DIPG findings on MRI.   Atypical MRI findings were defined as:
a) extended beyond the pons
b) had a well-defined, localized enhancing part with in a high intensity lesion on T2-weighted images.

Seven patients underwent open biopsy because of diffuse lesions in the pons that were not typical for DIPG. Four patients had a focal enhancing lesion, five had extension beyond the pons and two had both.  
The biopsy revealed:
5- diffuse brainstem glioma
1- PNET
1-pilocytic astrocytoma

There were no biopsy related deaths or intra-operative complications.  One child has transient worsening of hemiparesis.

The 12 year-old child harboring a PNET presented with double vision, unsteady gait and a facial palsy.  His tumor had focal enhancement but no extension beyond the pons.  The child received craniospinal radiation with tumor boost and chemotherapy as would be done for a supratentorial PNET with marked shrinkage.  At 13 months the tumor recurred near the genu of the corpus collosum.  This lesion had radiosurgery.

The 7 year old female with a pilocytic astrocytoma presented with difficulty speaking.   Her tumor did not enhance but extended beyond the pons into the right cerebellar peduncle and pons.  She did not have radiation but rather carboplatin and vincristine.   At the time of article submission the tumor had been stable for 9 month.

So, of the 5 children found to have high grade gliomas three of these had areas of focal enhancement and four had extension outside the pons.   The presenting symptoms included only right hemiparesis in one, only a facial palsy in one and lethargy in one.   Only two children had 2 symptoms of the typical triad.  One child had gait disturbance and facial palsy and the other had gait disturbance and hemiparesis.  Of these 5 high-grade glioma children, four of the tumors regrew within 7months( range 3-7 months).  Two of these children had died at the time of publication.

From this very small sample it seems there is no way to predict by MRI pathology without biopsy in atypical diffuse pontine tumors.   The article concluded that "an open biopsy of intrinsic brainstem lesions is considered safe and effective for selecting appropriate course of therapy".

References:
The efficacy of biopsy of intrinsic brainstem lesions for decision making of treatment.Childs Nerv Syst. 2013 Feb 3. [Epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/23377758

Biopsy Consensus Statements on DIPGs

Over the last few years there have been rapid change in treating and understanding pediatric brain tumors.   Per this recently electronically published article in Neuro Oncology these include :
1) Brainstem tumors are now considered to be safe targets for either stereotactic or open biopsy;
2) Age is a major factor interacting with tumor behavior (progression risk);
3) Recent research identifying new biologic markers of tumor classification and new druggable targets for trials has provided and opportunity to explore novel approaches to therapy.

In  February 2011, the second Consensus Conference on Pediatric Neurosurgery (CPN 2011) was held in Paris, France with the objective to establish a new consensus on surgical approaches to pediatric gliomas.   Statements on high grade gliomas, hypothalamic chiasmatic gliomas and diffuse intrinsic pontine gliomas were developed.  Statements  were disseminated to the 92 participants for a vote.  A statement was accepted if there was more than 70% of votes in favor of the statement.

Here are the final statements regarding DIPGs.
Typical DIPG
Biopsy of  a typical DIPG (defined by a short history and typical imaging findings) is justified when the patient is part of an ethically approved clinical study in which the tissue obtained will be used to investigate or inform the role of biological markers after treatment selection or molecular tumor grading.

Atypical Pontine Region Tumors
(A) Biopsy by an experienced pediatric neurosurgeon is indicated to confirm the diagnosis and guide therapy,
(B) An atypical pontine region tumor would be considered separately from classic DIPG for therapy or research purposes.

Authors of the final consensus paper included:
* David A Walker- Nottingham, United Kingdom
* JoFen Liu- Boston, USA
* Mark Kieran- Boston,  USA
* Nada Jabado- Quebec, Canada
* Susan Picton- Leeds, United Kingdom
* Roger Packer- Washington, USA
* Christian St. Rose - Paris, France

References:
A multi-disciplinary consensus statement concerning surgical approaches to low grade, high grade astrocytomas and diffuse intrinsic pontine gliomas (CPN Paris 2011) using the Delphi method.
Neuro Oncol 2013 March 15 [epub ahead of print]
http://www.ncbi.nlm.nih.gov/pubmed/23502427