Trop2 dependent and independent mechanisms of self-renewal in human cancer stem cells

Trop2 dependent and independent mechanisms of self-renewal in human cancer stem cells

Funding Type: 
Basic Biology IV
Grant Number: 
RB4-06209
Award Value: 
$1,254,960
Disease Focus: 
Cancer
Prostate Cancer
Stem Cell Use: 
Cancer Stem Cell
Status: 
Active
Public Abstract: 
Progress from our group and others has led to the identification of normal prostate tissue stem cells and the definition of important signaling pathways that regulate their growth and maintenance. Human cancers utilize these same pathways to promote malignancy and drive tumor progression. Our recent studies have uncovered an important regulatory molecule (Trop2) that is expressed on a subset of prostate cancer cells capable of regenerating tumors. Trop2 expression is selected for in advanced disease and predicts poor prognosis for many tumors including prostate, ovarian, pancreatic, breast, gastric and colorectal cancer. We predict that blocking Trop2 and other regulatory signaling pathways will be an effective strategy to prevent disease progression in prostate and other human cancers.
Statement of Benefit to California: 
In 2012 alone in the state of California, an estimated 29,000 men will be diagnosed with prostate cancer and almost 3,400 men will die from the disease. The advanced stages of prostate cancer are treated with hormonal therapy which causes significant changes in mood, body weight and composition, impotence and gynecomastia in addition to the pain and suffering from the disease. Our proposed experiments will define new therapeutic targets and combinatorial therapies with the potential to significantly extend life and minimize suffering of men with advanced prostate cancer. Many of the molecules that we are investigating are implicated in a range of tumors, suggesting that our findings may provide benefit to patients suffering from numerous cancers.
Progress Report: 

Year 1

Stem cells are characterized by longevity, self-renewal throughout the lifetime of a tissue or organism and the ability to generate all lineages of a tissue. Pathways involved in stem cell function are commonly dysregulated in cancer. Emerging evidence in leukemias and epithelial cancers suggests that tumors can be maintained by self-renewing cancer stem cells (CSCs), defined functionally by their ability to regenerate tumors. Delineating mechanisms that regulate self-renewal in human CSCs are essential to design new therapeutic strategies to combat cancer. We have developed an in vivo tissue-regeneration model of primary human prostate cancer and identified two distinct populations of CSCs that can self-renew and serially propagate tumors. Both CSC subsets express the transmembrane protein Trop2. We have previously shown that Trop2 is a marker and a new regulator of stem/progenitor activity in the prostate. Trop2 controls self-renewal, proliferation and tissue hyperplasia through two cleavage products—intracellular domain (ICD) and extracellular domain (ECD) generated by regulated intramembrane proteolysis (RIP). RIP of Trop2 is carried out by TACE metalloprotease and gamma-secretase complex. We have also demonstrated that cleaved Trop2 ICD is found in human prostate cancer but not in the cancer-adjacent benign tissue, suggesting a role for Trop2 cleavage in tumorigenesis. Now we are generating antibodies that will block Trop2 cleavage and activation. Blocking Trop2 signaling will be an effective strategy to prevent disease progression not only in the prostate but also in other epithelial cancers.

Year 2

Stem cells are characterized by longevity, self-renewal throughout the lifetime of a tissue or organism and the ability to generate all lineages of a tissue. Pathways involved in stem cell function are commonly dysregulated in cancer. Emerging evidence in leukemias and epithelial cancers suggests that tumors can be maintained by self-renewing cancer stem cells (CSCs), defined functionally by their ability to regenerate tumors. Delineating mechanisms that regulate self-renewal in human CSCs are essential to design new therapeutic strategies to combat cancer. We have developed an in vivo tissue-regeneration model of primary human prostate cancer and identified two distinct populations of CSCs that can self-renew and serially propagate tumors. Both CSC subsets express the transmembrane protein Trop2. We have previously shown that Trop2 is a marker and a new regulator of stem/progenitor activity in the prostate. Trop2 controls self-renewal, proliferation and tissue hyperplasia through two cleavage products—intracellular domain (ICD) and extracellular domain (ECD) generated by regulated intramembrane proteolysis (RIP). RIP of Trop2 is carried out by TACE metalloprotease and gamma-secretase complex. We have also demonstrated that cleaved Trop2 ICD is found in human prostate cancer but not in the cancer-adjacent benign tissue, suggesting a role for Trop2 cleavage in tumorigenesis. So far we generated seventeen antibodies against Trop2. Currently we are testing the inhibitory effect of the antibodies on Trop2 cleavage and activation. Blocking Trop2 signaling will be an effective strategy to prevent disease progression not only in the prostate but also in other epithelial cancers.

© 2013 California Institute for Regenerative Medicine