Targeting a SUMO editing enzyme to increase replication stress in cancer cells

Precision Medicine: Pathology to Population Health
Project outline

We aim to:
1. Identify how the SUMO protease, SENP7, protects cells from replicative stress.
2. Show whether repression of SENP7 reduces tumour growth in two cancer models.
3. Generate a platform for compound screening and test already shortlisted compound hits.
Hypothesis, SENP7 is required for survival of cells undergoing replicative stress, such as cancer cells, and is a potential small molecule target for improving cancer treatment.

Research Plan (Overview: Fig 1J)

1. Identify how SENP7 protects cells from replicative stress.
We will identify which portions of SENP7 function are required for controlling replication stress by complementation of SENP7 depleted cells with mutants (as in our publication [3]).Through the DNA fibre technique, which uses nucleotide analogue labelling of newly replicated DNA, we will distinguish slow replication fork progression, from fork collapse or collisions.

2. Show whether repression of SENP7 reduces tumour growth in cancer models.
We will introduce a cassette bearing Senp7 shRNA expressed from an inducible promoter into cancer cells. The cells will include those with replication stress (RasV12) and colon cancer lines (where high SENP7 and poor survival are clearly correlated (Fig 1K)). Cells with and without SENP7 will be tested for proliferation and drug sensitivity in tissue culture and in subcutaneous mouse xenografts.

3. Generate a platform for compound screening and test already shortlisted compound hits.
In collaboration with Prof Ray Owens and at Harwell we will identify the best system for SENP7 protein expression and purification. Dr Butterworth (UoB) has prioritised several compounds based on active compound clusters, drug-like properties and structural diversity as possible SENP inhibitors from previous high through-put screens (Sanford-Burnham Medical Research Institute). Cleavage of a SUMO-SUMO bond will be assessed in vitro and our SENP7 MEF series tested for replication faults induced by the compounds. This process will be iterative, testing derivative molecules.

Expected out comes and impact.
This project aims to validate a promising biomarker and/or small molecule target for use in cancer treatment. A successful outcome will lead to drug-discovery projects with MRCT or CRT or Biomarker applications. Thus the potential impact of this project is in increased UK economic output and improved population health. At the least this project will identify how this understudied factor, SENP7, promotes survival of cells with replicative stress. Since this type of stress is important in cancer development and ageing the results are likely to contribute to future interventions towards improving human health. MRC Special Skills Training: imaging, organism physiology, in vivo training.