Investigating the importance of translation elongation in B cell malignancies through modulation of the eEF2K/eEF2 signalling axis.

Title: Teaching old drugs new tricks: can blood cancer patients benefit from repurposed drugs?

Non-Hodgkin lymphomas (NHL) are a group of white blood cell cancers that mainly affect cells called B lymphocytes (B-NHL). These cancers represent ~4% of all cancers diagnosed in the UK annually (~14,000 cases/year). The treatments available for NHL patients still rely heavily on chemotherapy which can generate significant toxic side effects in all patients and can be too toxic for unfit or elderly patients to tolerate, due to additional underlying health problems such as heart conditions. Furthermore, patients can become develop resistance to the drugs. This results in the disease re-emerging (relapsing) due to cancer cells escaping initial treatment. Indeed 30-40% of patients with the commonest form of B-NHL relapse after treatment, representing a particular unmet clinical need. There is a requirement for new targeted treatments for NHL patients. In addition to developing better treatments, it is important that drugs are given to appropriate patients, providing personalised treatments. To ensure that this happens, molecular markers (biomarkers) can be developed that identify the patients that will benefit from specific treatments. In this way we will enhance the clinical management and survival prospects of B-NHL patients.

When normal cells become cancerous, they deregulate the processes controlling energy production to satisfy their increased need to fuel uncontrolled growth. One of the processes that requires significant amounts of energy is protein synthesis, the ability of cells to make new proteins. These newly generated proteins are responsible for driving disease progression increasing cell survival and replication. Our studies have identified that a protein called elongation factor-2 kinase (EF2K), normally responsible for inhibiting protein synthesis, is switched off in aggressive blood cancer cells, thus letting protein synthesis proceed in an uncontrolled manner. Our data show that EF2K in blood cancer cells is particularly sensitive to an established drug rapamycin, resulting in a reduction in disease progression. Furthermore, we have identified a drug called nelfinavir, originally approved to treat HIV patients in 1997, that has anti-cancer activities at least in part through the activation of EF2K. While nelfinavir is in clinical trials in breast, kidney lung cancers, the clinical activity of nelfinavir has not been tested in B-NHL. Therefore we will:

I. Determine whether EF2K is essential for the development of blood cancers by genetically altering blood cancer cells from mice or human patients, and testing the cells ability to grow and survive in our laboratory models;
II. Identify which specific types of B-NHL patients would benefit from EF2K targeting treatments by screening a range of B-NHL patient samples, featuring slow-growing and aggressive cancers, to test EF2K activity;
III. Establish whether drugs that activate of EF2K represent a valid therapeutic strategy blood cancer patients by conducting drug tests in our models and comparing the ability of rapamycin or nelfinavir to reduce or eradicate disease.
IV. Discover potential new drug targets that are regulated by EF2K-mediated protein synthesis and responsible for driving blood cancer progression by performing detailed analyses of human- and mouse-derived blood cancer cells and testing whether these new targets are responsive to rapamycin or nelfinavir treatment.

As EF2K has been shown to play an central role in the regulation of a number of different diseases involving learning and memory, heart and many cancers, the results generated in this proposal will be of use to a number of fields in addition to blood cell cancers. This study will also provide us with important information about how to develop nelfinavir, a safe oral drug, for use in human B-NHL clinical trials in the future.

The approval of small molecule inhibitors has revolutionised the clinical standard of care for patients with B cell Non-Hodgkin lymphomas (B-NHL). However, these treatments are not suitable for all B-NHL patients due to disease heterogeneity, and critically, these drugs are not curative with resistance mutations enable clonal evolution. Thus, identifying novel therapeutic strategies for patients that experience poor outcomes remains a priority research area for leukaemia/lymphoma translation. We have established a key role for mechanistic target of rapamycin (mTOR) in chronic lymphocytic leukaemia (CLL) maintenance/progression in promoting leukaemia development, relating to regulation of protein synthesis, specifically mRNA translation elongation through eEF2K/eEF2 signalling. Aggressive leukemic cells exhibited enhanced sensitivity to mTORC1 inhibitor rapamycin, compared with mTORC1/2 inhibitor AZD2014 in vivo. Rapamycin treatment alleviated inhibition of eEF2K which in turn inhibited mRNA translation elongation, as indicated by increased p-eEF2 and reduced expression MCL1. These studies are the first to identify translation elongation as a novel therapeutic target in leukaemia models, and have led us to hypothesise that eEF2K and EF2 play a critical role in driving the pathogenesis of aggressive B-NHLs. By genetically altering eEF2K/eEF2 signalling either in our leukaemia mouse models or proliferating primary CLL cells, we will determine the fundamental role of eEF2K signalling in leukaemia progression. These findings coupled with screening of a spectrum of indolent/aggressive B-NHL samples will enable us to pinpoint which B-NHL patient subsets could benefit from therapeutic interventions targeting translation elongation. We will then conduct detailed biochemical and pre-clinical analyses of the eEF2K modulators, rapamycin and protease inhibitor nelfinavir, to exploit the therapeutic potential of targeting translation elongation initially in CLL, and then B-NHL.