Elevated CBP/p300 Expression Linked to Poor Outcomes in Advanced Prostate Cancer - Ayesha Shafi
November 7, 2024
Andrea Miyahira speaks with Ayesha Shafi about a study on AR coactivators CBP/p300 in prostate cancer. The research reveals that CBP/p300 expression increases as prostate cancer progresses to castration-resistant stages, correlating with poor patient survival. Through various preclinical studies, Dr. Shafi demonstrates that CBP/p300 plays a crucial role in DNA repair, particularly in homologous recombination pathways. The study explores the potential of targeting CBP/p300 using the inhibitor CCS1477 (inobrodib), especially in combination with DNA-damaging agents like PARP inhibitors. The discussion highlights the therapeutic implications of these findings and future research directions, including investigating combination therapies and understanding the mechanism of action through cistromic and transcriptomic analyses.
Biographies:
Ayesha Shafi, PhD, Assistant Professor, Center for Prostate Disease Research, Uniformed Services University, Walter Reed Surgery, Bethesda, MD
Andrea K. Miyahira, PhD, Director of Global Research & Scientific Communications, The Prostate Cancer Foundation
Biographies:
Ayesha Shafi, PhD, Assistant Professor, Center for Prostate Disease Research, Uniformed Services University, Walter Reed Surgery, Bethesda, MD
Andrea K. Miyahira, PhD, Director of Global Research & Scientific Communications, The Prostate Cancer Foundation
Read the Full Video Transcript
Andrea Miyahira: Hi everyone, I'm Andrea Miyahira here at the Prostate Cancer Foundation. Joining me is Dr. Ayesha Shafi of the Center for Prostate Disease Research. She will share her recent paper "AR Coactivators CBP/p300 Are Critical Mediators of DNA Repair in Prostate Cancer." This was published in Oncogene. Dr. Shafi, thanks so much for joining us.
Ayesha Shafi: Thanks, Andrea. Thank you for having me. I'm excited to present our work today with you guys. Just to get us all on the same page, I'm just going to give us a little bit of background on the current challenges we face in 2024 in prostate cancer, specifically metastatic castration-resistant prostate cancer, or CRPC, remains a uniformly fatal disease. And unlike breast cancer, prostate cancer doesn't have many subtypes. Most patients are treated very similarly. Recently, PARP inhibitors were approved for BRCA2-deficient tumors. More work needs to be done for us to better understand this disease, to understand the different molecular subtypes, and to develop more effective treatments. What we need are these validated targeted therapies that act in concert with standard of care such as androgen deprivation or AR antagonists like enzalutamide and so forth. I'm hoping today what I'll show you one such potential target are these coactivators CBP/p300. What are they?
They are coactivators of the androgen receptor that help in its transcriptional function and downstream signaling. Why do we care about them? When we look at publicly available prostate cancer data sets on Stand Up to Cancer or seen on the portal from the Stand Up to Cancer Dream Team data here, we can appreciate that CBP/p300 expression increases as the disease progresses from hormone-sensitive prostate cancer, early-stage disease, to castration-resistant prostate cancer, or the lethal stage of the disease. It's characterized by this elevation or increase in CBP expression. Here our collaborators from Johann de Bono's group showed patients' expression from hormone-sensitive prostate cancer via either needle biopsy or radical prostatectomy, and also patients from castration-resistant prostate cancer from lymph node metastases or bone mets. And looking at IHC expression, which is quantified to the right to show this increase—for this one is CBP.
And importantly, why do we care about this? Because patients that have high CBP or high p300 have lower survival probability, looking at a cohort of prostate cancer patients. As the disease progresses, it's characterized by this increase in CBP/p300, which is associated with poor outcome. One of the first things we were asking, is it targetable? And we have collaborated with our industry partner CellCentric, that developed an inhibitor for CBP/p300, known as CCS1477 or inobrodib. That's in phase one clinical trials. Our initial study showed its role in mediating CBP/p300 through AR-MYC signaling. And this follow-up study, we now showed its role in mediating DNA damage. Here you can just appreciate what we've performed growth expression or survival in two different CRPC models, the 22RV1s and C42s, in combination with different DNA repair agents including radiation, cisplatin, olaparib, which is a PARP inhibitor, and doxorubicin, which causes double-strand breaks.
Here you can see the combination treatment of inhibiting CBP/p300 in combination with DNA-damaging agents have an enhanced growth suppression. And next we wanted to understand what's the transcriptional function of CBP/p300? We performed transcriptomics or RNA-seq in our inducible knockdown models. And this is our CRPC model where we can knock down expression of CBP or p300. We performed RNA-seq. You can see a vast difference in transcript levels that are changed when we either knocked down CBP or p300. And we looked at all these transcripts to see what was in common. In our two different conditions, we got 3,000 genes that we performed pathway analysis and saw several DNA repair pathways that were altered. Then we took an unbiased approach to compare all these 3,000 common CBP/p300-regulated genes and compared them to the MSigDB database of DNA repair-regulated pathways.
And therefore we generated a list of CBP/p300-regulated DNA damage repair genes, which we then characterized into the five main DDR pathways. This includes homologous recombination, non-homologous end joining, base excision repair, nucleotide excision repair, and mismatch repair. Here, hopefully you can appreciate of the five DDR pathways, the homologous recombination or HR is the most altered or regulated by CBP/p300, almost 25%, a quarter of these HR genes are CBP/p300-mediated. Here's just a list of those genes. Then we wanted to understand is there any functional relevance of HR mediation by CBP/p300? And to do this, we performed several preclinical assays. Here I'm just showing you a few that we did. We first looked at the expression of key HR targets, including ATM, CHEK2, RAD50 in the presence of damage. In this case, we used radiation outlined in red as our positive control to induce expression.
And we looked at the effect of either inhibiting CBP/p300 through the CCS compound or inducibly knocking down individually CBP/p300 expression. What you can see is that when CBP/p300 is inhibited or knocked down, there's a significant decrease in HR gene expression, which you can see in orange and in blue and green here. Next we wanted to translate these in vitro results to see if they translated in vivo. And we performed xenograft studies in our CRPC models, treated the mice with CBP/p300 inhibitor. And here you can see again a few of the HR genes including RAD50 and MRE11. In the condition of the cells treated with CBP/p300 inhibition, there's a significant decrease in these HR factors. Lastly, we then looked at it translationally to patients using patient-derived xenograft models. And here's one model again treated with CBP/p300 inhibitor, and you can see a reduction in RAD50 and MRE11.
Importantly, in this particular PDX model, when we gave long-term treatment of CBP/p300 inhibition, this patient stopped responding. And similarly, you saw that corresponding increase in HR targets as well. What I've shown you today from our study that was published recently was that as the disease progresses from primary localized prostate cancer to castration-resistant prostate cancer, it is characterized by this elevation of high CBP, high p300 expression due to the genes themselves being amplified. And this is associated with poor outcome. And in the presence of DNA damage causing double-strand breaks, CBP/p300 mediate this repair through promoting homologous recombination factors to mediate repair and subsequent cell survival. And what we're working with is our industry partners targeting CBP/p300 as a potential therapeutic target to mediate in combination DNA repair and then ultimately decrease tumor growth. With that, I'd like to thank the large collaborative group effort on this. That was done with my group, my former group under Karen Knudsen at Jefferson, other collaborators here at CPDR, Johann de Bono's group and collaborators, Lisa Butler's group and CellCentric, and the rest of our colleagues here and our funding sources, specifically PCF, which funded part of this. Thank you.
Andrea Miyahira: Thank you so much, Dr. Shafi, for sharing that with us. Is it known what mechanisms are up-regulating CBP and p300 in prostate cancer as disease advances?
Ayesha Shafi: That's a great question and there are several factors that play a role in this, including genetic modification, which I briefly touched on. What we showed is examining publicly available data sets of prostate cancer that there's amplification in both CBP and p300 in patients as they go from primary disease to metastatic prostate cancer. And there's also other factors that other people have shown that regulate CBP/p300 expression, including transcription factors such as MYC or E2F drive expression, epigenetic regulators that can affect the acetylation that affect their expression, and hormone signaling such as androgens that can impact it.
Andrea Miyahira: Thank you. And what therapeutic strategy do you think would be most effective for targeting p300-CBP? Should we be using combination therapies? Should we be targeting patients who have DDR mutations based on your research?
Ayesha Shafi: This is a great question. Our study showed that CBP/p300 plays a role in mediating potentially homologous recombination or HR. And our in vitro studies that I showed indicated that using the CBP/p300 inhibitor in combination with DNA-damaging agents such as olaparib, which is PARP inhibitor, resulted in this enhanced growth suppression. With this in mind, we believe that combination with PARP inhibitors would be most effective specifically in patients with HR defects because this has the potential to capitalize on the aspect of synthetic lethality. This could be a great avenue that we're actively pursuing.
Andrea Miyahira: Thank you. And what are the next steps for these studies?
Ayesha Shafi: Timely into that, one of them is looking at this combinational therapy. We want to understand the mechanism of action of CBP/p300 mediating DNA damage repair, and we also want to understand—we're actively looking at mimicking what we see in the patients so we can understand better responders versus non-responders. One of the things we want to do is understand the cistromic and transcriptomic landscape by performing ATAC-seq, RNA-seq in these high MYC, high AR conditions to see what occurs. And then we also want to understand what could also be in complex with CBP/p300 as potential other targets using proteomic studies, and then delve more into this DNA repair mechanism of action. Those are some ongoing studies that we have.
Andrea Miyahira: I'm looking forward to it. Thanks so much for sharing this with us today.
Ayesha Shafi: Thank you for having me.
Andrea Miyahira: Hi everyone, I'm Andrea Miyahira here at the Prostate Cancer Foundation. Joining me is Dr. Ayesha Shafi of the Center for Prostate Disease Research. She will share her recent paper "AR Coactivators CBP/p300 Are Critical Mediators of DNA Repair in Prostate Cancer." This was published in Oncogene. Dr. Shafi, thanks so much for joining us.
Ayesha Shafi: Thanks, Andrea. Thank you for having me. I'm excited to present our work today with you guys. Just to get us all on the same page, I'm just going to give us a little bit of background on the current challenges we face in 2024 in prostate cancer, specifically metastatic castration-resistant prostate cancer, or CRPC, remains a uniformly fatal disease. And unlike breast cancer, prostate cancer doesn't have many subtypes. Most patients are treated very similarly. Recently, PARP inhibitors were approved for BRCA2-deficient tumors. More work needs to be done for us to better understand this disease, to understand the different molecular subtypes, and to develop more effective treatments. What we need are these validated targeted therapies that act in concert with standard of care such as androgen deprivation or AR antagonists like enzalutamide and so forth. I'm hoping today what I'll show you one such potential target are these coactivators CBP/p300. What are they?
They are coactivators of the androgen receptor that help in its transcriptional function and downstream signaling. Why do we care about them? When we look at publicly available prostate cancer data sets on Stand Up to Cancer or seen on the portal from the Stand Up to Cancer Dream Team data here, we can appreciate that CBP/p300 expression increases as the disease progresses from hormone-sensitive prostate cancer, early-stage disease, to castration-resistant prostate cancer, or the lethal stage of the disease. It's characterized by this elevation or increase in CBP expression. Here our collaborators from Johann de Bono's group showed patients' expression from hormone-sensitive prostate cancer via either needle biopsy or radical prostatectomy, and also patients from castration-resistant prostate cancer from lymph node metastases or bone mets. And looking at IHC expression, which is quantified to the right to show this increase—for this one is CBP.
And importantly, why do we care about this? Because patients that have high CBP or high p300 have lower survival probability, looking at a cohort of prostate cancer patients. As the disease progresses, it's characterized by this increase in CBP/p300, which is associated with poor outcome. One of the first things we were asking, is it targetable? And we have collaborated with our industry partner CellCentric, that developed an inhibitor for CBP/p300, known as CCS1477 or inobrodib. That's in phase one clinical trials. Our initial study showed its role in mediating CBP/p300 through AR-MYC signaling. And this follow-up study, we now showed its role in mediating DNA damage. Here you can just appreciate what we've performed growth expression or survival in two different CRPC models, the 22RV1s and C42s, in combination with different DNA repair agents including radiation, cisplatin, olaparib, which is a PARP inhibitor, and doxorubicin, which causes double-strand breaks.
Here you can see the combination treatment of inhibiting CBP/p300 in combination with DNA-damaging agents have an enhanced growth suppression. And next we wanted to understand what's the transcriptional function of CBP/p300? We performed transcriptomics or RNA-seq in our inducible knockdown models. And this is our CRPC model where we can knock down expression of CBP or p300. We performed RNA-seq. You can see a vast difference in transcript levels that are changed when we either knocked down CBP or p300. And we looked at all these transcripts to see what was in common. In our two different conditions, we got 3,000 genes that we performed pathway analysis and saw several DNA repair pathways that were altered. Then we took an unbiased approach to compare all these 3,000 common CBP/p300-regulated genes and compared them to the MSigDB database of DNA repair-regulated pathways.
And therefore we generated a list of CBP/p300-regulated DNA damage repair genes, which we then characterized into the five main DDR pathways. This includes homologous recombination, non-homologous end joining, base excision repair, nucleotide excision repair, and mismatch repair. Here, hopefully you can appreciate of the five DDR pathways, the homologous recombination or HR is the most altered or regulated by CBP/p300, almost 25%, a quarter of these HR genes are CBP/p300-mediated. Here's just a list of those genes. Then we wanted to understand is there any functional relevance of HR mediation by CBP/p300? And to do this, we performed several preclinical assays. Here I'm just showing you a few that we did. We first looked at the expression of key HR targets, including ATM, CHEK2, RAD50 in the presence of damage. In this case, we used radiation outlined in red as our positive control to induce expression.
And we looked at the effect of either inhibiting CBP/p300 through the CCS compound or inducibly knocking down individually CBP/p300 expression. What you can see is that when CBP/p300 is inhibited or knocked down, there's a significant decrease in HR gene expression, which you can see in orange and in blue and green here. Next we wanted to translate these in vitro results to see if they translated in vivo. And we performed xenograft studies in our CRPC models, treated the mice with CBP/p300 inhibitor. And here you can see again a few of the HR genes including RAD50 and MRE11. In the condition of the cells treated with CBP/p300 inhibition, there's a significant decrease in these HR factors. Lastly, we then looked at it translationally to patients using patient-derived xenograft models. And here's one model again treated with CBP/p300 inhibitor, and you can see a reduction in RAD50 and MRE11.
Importantly, in this particular PDX model, when we gave long-term treatment of CBP/p300 inhibition, this patient stopped responding. And similarly, you saw that corresponding increase in HR targets as well. What I've shown you today from our study that was published recently was that as the disease progresses from primary localized prostate cancer to castration-resistant prostate cancer, it is characterized by this elevation of high CBP, high p300 expression due to the genes themselves being amplified. And this is associated with poor outcome. And in the presence of DNA damage causing double-strand breaks, CBP/p300 mediate this repair through promoting homologous recombination factors to mediate repair and subsequent cell survival. And what we're working with is our industry partners targeting CBP/p300 as a potential therapeutic target to mediate in combination DNA repair and then ultimately decrease tumor growth. With that, I'd like to thank the large collaborative group effort on this. That was done with my group, my former group under Karen Knudsen at Jefferson, other collaborators here at CPDR, Johann de Bono's group and collaborators, Lisa Butler's group and CellCentric, and the rest of our colleagues here and our funding sources, specifically PCF, which funded part of this. Thank you.
Andrea Miyahira: Thank you so much, Dr. Shafi, for sharing that with us. Is it known what mechanisms are up-regulating CBP and p300 in prostate cancer as disease advances?
Ayesha Shafi: That's a great question and there are several factors that play a role in this, including genetic modification, which I briefly touched on. What we showed is examining publicly available data sets of prostate cancer that there's amplification in both CBP and p300 in patients as they go from primary disease to metastatic prostate cancer. And there's also other factors that other people have shown that regulate CBP/p300 expression, including transcription factors such as MYC or E2F drive expression, epigenetic regulators that can affect the acetylation that affect their expression, and hormone signaling such as androgens that can impact it.
Andrea Miyahira: Thank you. And what therapeutic strategy do you think would be most effective for targeting p300-CBP? Should we be using combination therapies? Should we be targeting patients who have DDR mutations based on your research?
Ayesha Shafi: This is a great question. Our study showed that CBP/p300 plays a role in mediating potentially homologous recombination or HR. And our in vitro studies that I showed indicated that using the CBP/p300 inhibitor in combination with DNA-damaging agents such as olaparib, which is PARP inhibitor, resulted in this enhanced growth suppression. With this in mind, we believe that combination with PARP inhibitors would be most effective specifically in patients with HR defects because this has the potential to capitalize on the aspect of synthetic lethality. This could be a great avenue that we're actively pursuing.
Andrea Miyahira: Thank you. And what are the next steps for these studies?
Ayesha Shafi: Timely into that, one of them is looking at this combinational therapy. We want to understand the mechanism of action of CBP/p300 mediating DNA damage repair, and we also want to understand—we're actively looking at mimicking what we see in the patients so we can understand better responders versus non-responders. One of the things we want to do is understand the cistromic and transcriptomic landscape by performing ATAC-seq, RNA-seq in these high MYC, high AR conditions to see what occurs. And then we also want to understand what could also be in complex with CBP/p300 as potential other targets using proteomic studies, and then delve more into this DNA repair mechanism of action. Those are some ongoing studies that we have.
Andrea Miyahira: I'm looking forward to it. Thanks so much for sharing this with us today.
Ayesha Shafi: Thank you for having me.