A highly aggressive common form of leukaemia which is activated by mutations in signalling molecules is maintained by a web of regulatory proteins downstream of these signals.  

New research published in Cell Reports shows that a complex network of interacting genes activated by this altered signalling may be able to be manipulated to kill off Acute Myeloid Leukaemia (AML) cancer cells.

This study by an international team of researchers from the University of Birmingham, Newcastle University, the Princess Maxima Centre of Pediatric Oncology in Utrecht and the University of Virginia, USA has used advanced screening tools to identify how gene regulatory networks (GRNs) maintain a sub-type of blood cancer called FLT3-ITD mutated AML.

Using this AML model, the researchers have identified connections between proteins called transcription factors (TF) and the genes they bind to that together form a complex network (GRN) that is highly specific for FLT3-ITD AML cells as compared to healthy cells.

Using a screening method developed in Newcastle, the researchers identified about 100 genes within this GRN that are important for AML growth and survival. They homed in on several of these genes to study the effect of targeting them. The TF RUNX1 was studied in fine detail and the analyses showed that RUNX1 is a key factor in keeping the GRN stable.

Significantly, the RUNX1 protein could be blocked by using a small molecule inhibitor developed by Prof John Bushweller of the University of Virginia, leading to the collapse of the network that maintains FLT3-ITD AML.

Professor Constanze Bonifer and Professor Peter Cockerill who are the senior authors of the paper from the Institute of Cancer and Genomic Sciences at the University of Birmingham comment:

“The FLT3-ITD sub-type of acute myeloid leukaemia that we have been studying has very poor outcomes with high relapse rates among those who do go into remission. We set out to identify very specific targets that are required for AML cancer cells to regulate themselves, that could potentially lead to new treatments.

“We are delighted to have identified multiple factors, including TFs and signalling proteins that have key roles in maintaining these gene regulation networks where TFs and genes are wired in an AML- specific way.  Such networks act a bit like a computer programme that runs processes to maintain AMLs and which are different to those networks found in normal cells. Our research has found that knocking out such factors resulted in the network shutting down, and which may lead to the cancer cells dying off as they are unable to replicate.”

Modelling AML

To identify potential protein targets that regulate AML cancer cells, the researchers mapped the transcription factor binding sites within AML-specifically expressed genes. The team then compared normal to malignant cells to work out which genes could promote AML survival and targeted them specifically.

The team then used a type of screening technique called shRNA to look at individual-specific factors’ roles in maintaining the network found in AML. As the TFs operate within an interactive network, the team then observed the effect of targeting individual factors on the rest of the network and found that specific proteins including RUNX1 were crucial for the maintenance of the GRN as a whole.

Professor Olaf Heidenreich who is a co-grant holder on this project with his colleague Dr. Helen Blair from Newcastle and who is now at the Princess Maxima Centre for Paediatric Oncology in Utrecht said

“Many researchers in the world use techniques called “genome-wide screening” where they eliminate every gene in cancer cells to identify those genes that are essential for the growth of these cells. However, this method identifies many genes that are also required for healthy cells. Therefore, finding genes that are only important for cancer cells is a bit like finding a needle in a haystack. Identifying the gene regulatory networks that are specific for cancer cells makes this talks much easier.”

“Besides testing the effect of select targets on AML growth, our work will provide an important resource for the scientific community to home in on the targets that really matter”.

This research was funded by the MRC, by Leukaemia UK and by Blood Cancer UK.

Source: University of Birmingham