Investigating the role of P-Rex1 in mouse models of melanoma
Lead Research Organisation:
Cancer Research UK Beatson Institute
Department Name: Research Group 18 (Owen Sansom)
Abstract
The skin cancer malignant melanoma (MM) is increasing in rate more than any other common cancer in the UK, and is doubling in rate every 10-20 years in Western countries. Early spread of MM to other organs is nearly always the cause of death from this cancer. Identifying and studying new proteins which are both responsible for this spread and treatable is crucial for this cancer which is known for being unresponsive to traditional therapies.
We have genetically removed a protein called P-Rex1 from black mice, and discovered that their bellies and feet remain white. These white areas suggest that melanocytes (the skin cells responsible for MM) aren‘t reaching the furthest regions of migration during normal mouse development. We also know that the genetic changes required for melanocyte movement during development are very similar to the genetic changes required during MM tumour spread. Therefore we have obtained mice which develop human-like melanomas and I plan to assess if removing P-Rex1 can stop the lethal migration of melanocytes (known as metastasis) to other organs. I will also analyse resected human melanoma specimens to evaluate P-Rex1 in a comprehensive manner which is correlated with how well the patient did with their melanoma.
We have genetically removed a protein called P-Rex1 from black mice, and discovered that their bellies and feet remain white. These white areas suggest that melanocytes (the skin cells responsible for MM) aren‘t reaching the furthest regions of migration during normal mouse development. We also know that the genetic changes required for melanocyte movement during development are very similar to the genetic changes required during MM tumour spread. Therefore we have obtained mice which develop human-like melanomas and I plan to assess if removing P-Rex1 can stop the lethal migration of melanocytes (known as metastasis) to other organs. I will also analyse resected human melanoma specimens to evaluate P-Rex1 in a comprehensive manner which is correlated with how well the patient did with their melanoma.
Technical Summary
Aims: The incidence of malignant melanoma (MM) is increasing more than any other common cancer in the UK. Worldwide its incidence is doubling in rate every 10-20 years in countries with white populations. Metastasis is almost invariably the ultimate cause of death in MM. My aim is to study the impact of P-Rex1 on metastasis in humanised mouse models of melanoma.
Hypothesis: Several humanised mouse models of human melanoma have been characterised, reflecting both common gain-of-function mutations (BrafV600E, NrasQ61K) as well as loss-of-function in known MM tumour-suppressor genes (PTEN, CDKN2A). We have crossed a P-Rex1 knockout mouse to a pure C57BL6 background, revealing a previously uncharacterised ‘white belly‘ phenotype with matching white feet and tail. These areas are the extremities of melanoblast migration during embryogenesis, suggesting a migratory deficit of the cells. Previous work done in our laboratory has also shown P-Rex1 to be consistently up-regulated in a host of melanoma cell lines. I therefore hypothesised that P-Rex1 up-regulation is a central component of the melanocyte migration involved in melanoma metastasis.
Objectives:
1. To study incidence, latency, and localisation of MM primary tumours and metastasis between P-Rex1 knockout and WT mice crossed to both BrafV600E and NrasQ61K melanoma mouse models.
2. To apply both GFP and DCT-lacZ reporter constructs to the above genotypes in order to study melanoblast migration as a paradigm for MM metastasis.
3. To perform a comprehensive survey of P-Rex1 expression in a host of human melanoma samples (including tissue microarrays) and correlate with outcome data.
Design & Methodology:
We already have access to characterised BrafV600E and NrasQ61K mouse models of MM, as well as P-Rex1 knockout mice. With these mice I plan to perform a comprehensive cohort comparison study to answer my hypothesis with regard to objective 1. To fully characterise the MM model(s) I will use histological and immunohistochemistry (IHC) techniques. The transgenic expression of GFP or ?-galactosidase under the control of melanocyte-specific promoters will allow me to assess morphology, speed, and localisation of melanoblasts in various forms of MM genetically modified mice. I will further consolidate the importance of these signalling pathways using clinical MM tissue microarrays (TMA) to explore the role of P-Rex1 in primary and metastatic human samples.
Medical and Scientific Opportunities: Identifying and characterising novel proteins which are responsible for metastasis and amenable to therapeutic intervention is a priority for MM, which is characterised by its resistance to traditional chemotherapeutics and ability to metastasise early.
Hypothesis: Several humanised mouse models of human melanoma have been characterised, reflecting both common gain-of-function mutations (BrafV600E, NrasQ61K) as well as loss-of-function in known MM tumour-suppressor genes (PTEN, CDKN2A). We have crossed a P-Rex1 knockout mouse to a pure C57BL6 background, revealing a previously uncharacterised ‘white belly‘ phenotype with matching white feet and tail. These areas are the extremities of melanoblast migration during embryogenesis, suggesting a migratory deficit of the cells. Previous work done in our laboratory has also shown P-Rex1 to be consistently up-regulated in a host of melanoma cell lines. I therefore hypothesised that P-Rex1 up-regulation is a central component of the melanocyte migration involved in melanoma metastasis.
Objectives:
1. To study incidence, latency, and localisation of MM primary tumours and metastasis between P-Rex1 knockout and WT mice crossed to both BrafV600E and NrasQ61K melanoma mouse models.
2. To apply both GFP and DCT-lacZ reporter constructs to the above genotypes in order to study melanoblast migration as a paradigm for MM metastasis.
3. To perform a comprehensive survey of P-Rex1 expression in a host of human melanoma samples (including tissue microarrays) and correlate with outcome data.
Design & Methodology:
We already have access to characterised BrafV600E and NrasQ61K mouse models of MM, as well as P-Rex1 knockout mice. With these mice I plan to perform a comprehensive cohort comparison study to answer my hypothesis with regard to objective 1. To fully characterise the MM model(s) I will use histological and immunohistochemistry (IHC) techniques. The transgenic expression of GFP or ?-galactosidase under the control of melanocyte-specific promoters will allow me to assess morphology, speed, and localisation of melanoblasts in various forms of MM genetically modified mice. I will further consolidate the importance of these signalling pathways using clinical MM tissue microarrays (TMA) to explore the role of P-Rex1 in primary and metastatic human samples.
Medical and Scientific Opportunities: Identifying and characterising novel proteins which are responsible for metastasis and amenable to therapeutic intervention is a priority for MM, which is characterised by its resistance to traditional chemotherapeutics and ability to metastasise early.