The role of chromosomal abnormalities in cancer and experimental therapeutics

Cancer affects around a third of all adults during their life and as life expectancy increases, cancer incidence will increase in the following decades. The occurrence of mutations in cancer is indicative of specific changes that drive tumour development and which can be targets for new therapies that would not have the side effects as conventional treatments. One the most obvious changes seen in cancer cells is chromosomal translocation, which result from joining between two different chromosomes during cell division. These translocations usually have an effect on a gene or even fuse two genes together giving tumour-specific markers and new therapeutic targets. The problem is that these molecules are inside the cell and are not usually enzymes which can relatively easily be inactivated by drugs that are able to enter the cancer cells. We need new types of drugs to inactivate the chromosomal translocation-proteins and new ways of modelling chromosomal translocations to test out the novel drugs in an in vivo preclinical setting. The aim of the work proposed in the application is to develop new methods in both areas. We will develop ways to rapidly produce bespoke reagents that can interfere with chromosomal translocation-proteins to block cancer growth or, in some settings, to kill tumour cells whilst sparing normal counterparts. We will also develop methods to create in vivo models of human chromosomal translocations that can be used to assess the biological basis of cancer and as a setting for developing new therapeutic strategies. The aim is to evaluate the possible use of novel reagents for cancer patients in these models, either as single therapeutic entities or in combination with existing treatment modalities. Our long term aim is to treat patients with regimes shown to be effective in vivo.

The study of chromosomal translocations is important to understand cancer initiation and progression as well as providing new therapeutic targets and molecules that can be evaluated in the preclinical setting of mouse cancer models. Cancer arises by somatic genetic changes that include gross chromosomal abnormalities. Chromosomal translocations are particularly prevalent in haematopoietic and mesenchymal neoplasias and pinpoint an exact location in the genome where a change has occurred, at which an altered gene or gene fusion is found. Therefore defining and studying the breakpoint provides the means to quickly identify the genetic basis of the tumour formation that follows a chromosomal rearrangement. This is a powerful system in cancer biology to define the biological steps from the cancer stem cell to the overt tumour and its metastatic invasive stage. We will develop faster and more complex mouse models to mimic human cancer employing homologous recombination in ES cells and generation of mice from these. As an example, we will model the MLL-AF4 fusion to develop a system to study the leukaemia and analyse new drugs for this fusion-associated leukaemia which has a high incidence in childhood acute lymphoblastic leukaemia and is a poor prognostic indicator. The mouse models will form prototypes for testing macromolecular drugs (macrodrugs) and delivery systems for these. We will generate new molecules for interference with the function of oncogenic proteins in human cancer, including leukaemias, sarcomas and carcinomas. We have previously shown that single immunoglobulin variable region domains can be used as powerful functional entities inside cells to interact with targets and cause phenotypic knock-out. These intrabodies will be developed against key cancer targets such as MLL-AF4 in leukaemia or EWS-ERG or FLI1 in sarcoma. We will expand our range of techniques in the intrabody area to facilitate isolation of molecules that bind to defined parts of targets, such as the junctional region of fusion proteins. These molecules will be tested using in vivo models as a preclinical setting since novel therapies must be evaluated in the context of a model system prior to use in patients. In the medium term, we predict that we can use the reagents ex vivo with human cancers and ultimately in vivo either as macromolecular drugs in their own right or following development of mimetics.