IMPaCT Plenary Session: Therapeutics Video (Text Version) - Dr. Ching-Shih Chen

Title of Talk: Kinases, Epigenetics, and Energy Metabolism – Three Prongs in Anticancer Drug Discovery

Speaker
And hopefully you’ll be available afterwards for more questions if we have time permitting or—or in between sessions. Well I’d like to introduce next Dr. Ching-Shih Chen from the Ohio State University. Dr. Chen is the Lucius A. Wing Chair of Cancer Research and Therapy and Professor of Medicinal Chemistry in Internal Medicine and Neurology at Ohio State. He is—his research focuses on signaling pathways controlling cancer cell survival as targets for drug discovery and development and his drug platform has resulted in licensing of several new IND approvals as well as initiation of—of two clinical trials. And he’s received a number of funding awards and was elected a Fellow into the American Association of Advancement of Science in 2004. His training was at University of Rhode Island as well as the University of Kentucky. He received his Post-Doc training in Medicinal Chemistry at the University of Wisconsin Madison. Please welcome Dr. Chen to the podium; thank you.

Ching-Shih Chen, Ph.D.; Professor of Medicinal Chemistry and Internal Medicine, College of Pharmacy and Comprehensive Cancer Center, The Ohio State University, Lucius A. Wing Chair of Cancer Research and Therapy
Well thank you very much for the kind introduction. It’s I think a very exciting and very inspiring meeting because we heard so many outstanding talks. A recurrent theme in many talks is that you know this really is teamwork to fight cancer. The clinician, the basic scientist, the patient—we all work together to fight this prostate cancer. So our role is in this box; we are in the early drug discoveries. So we work with the clinicians to find out what are the rhythm targets for drug discoveries and we design and—and do the magnificent presentation and push forward to a clinical trial. And hopefully we can achieve from the bench to the clinic and back. This is our goal.

What—with the funding from DoD, Prostate Cancer Foundation, NCI, and many other agencies we are very fortunate to establish a very comprehensive research team. That’s allowed us to do the drug design and synthesis and do the magnificent validation and all the preclinical development in animals. So this has been our model, so we work very closely with oncologists to do this in clinical development and we also rely upon NCI to do some of the—the IND directives—the toxicology from oncology for us and eventually I would give you an examples—we find an industrial partner to do the clinical trials.

So there are three areas that constitute our focus. We are designing new kinase inhibitors that we hope can overcome drug resistance and then to overcome the aggressive phenotype in prostate cancer cells. So this is the first area of focus. The second area we are targeting, the epigenetics because this represents the fundamental of the cancer cells to suppress tumor suppressor genes to activate oncogenes. So through this epigenetic modulation, we are able to suppress—to block the tumor progression.

The third area recently we are developing is to target energy metabolism, the so called Walberg effect. So I will give examples to illustrate our approaches and the results of some of our recent findings. So we are able to establish a portfolio of agents targeting different assays in the area of kinase signaling, epigenetics, and energy metabolism. I think that also in many talks we have been told that the biggest problem in cancer—cancer therapy is the heterogeneity issue. So we have to rely upon a combination of drugs or drug with multiple mechanisms. So this is what we tried to accomplish. We tried to have an arsenal of agents available at—for the—for the oncologists to fight the disease. So some of the—this—these agents are at given stages of the—the development, and we are very lucky to have two agents that currently are into Phase 1 clinical trials. That is the—the PDK1 inhibitor and HDAC inhibitor.

So again through the funding of the—of many different agencies including DoD and Prostate Cancer Foundation, we are able to do this clinical translation. So the first drug that goes into the clinical trial is the one derived from a very famous drug, the COX2 inhibitor celecoxib. In the early 2000, we raised a question; is COX2 inhibition essential for the entire tumor effect of celecoxib. So we published two papers in a row; JNCI to prove otherwise. So we showed that—the effect of celecoxib was actually due to the inhibition of Akt. So based on this magnificent finding, we are able to use our medicinal chemistry expertise to disassociate the COX2 activity that improved the activity in Akt inhibition and then we came up with a drug OSU-03012. Very luckily this agent got accepted by the NCI rate process to IND direct toxicology and pharmacology and at the same time we were able to with the magnificent validation and it was licensed and it went into clinical trial. So it’s a very important—for us to see this translation and the—the drug was taken by the first patient in June 2009. So this is my second birthday. That’s for basic scientist to see the translation of his bench—bench research into clinical trial.

The other drug we have as a success is a HDAC inhibitor; that’s where we use a prototype compound called phenubuterate where we were able to improve the potency by 10,000 fold and prove more—more efficacious than SAHA and then has a [inaudible] in suppressing tumor growth without toxicity and again this went into clinical trial.

So with this success we were encouraged to continue our pursuit of new agents. And today I’m going to give you some examples in two areas. One is to overcome drug resistance and aggressive phenotypes. We are particularly interested in the subpopulation of prostate cancer cells which is the aldehyde dehydrogenase-positive prostate subpopulation. This subpopulation of cancer cells contributes to drug resistance and also some of the aggressive phenotypes with the prostate cancer metastases.

So we are—we have come up with this agent; the other target we are particularly interested in is tumor metabolism. So this is the so-called Walberg effect. So we have—we’ll give you example to show by targeting energy restriction we are able to block the tumor progression and to delay the onset of the—the prostate tumorigenesis. So in the area of the—the ALDH-positive subpopulation, we are interested in an enzyme called integrin linked kinase, abbreviated as ILK. ILK is a punitive PDK-2. As many of you have heard about Akt repeatedly in different—in different talks, Akt in cancer cells is an evil empire. That is, it’s contributed many of the aggressive phenotypes and also that the major survival mechanism in cancer cells. Earlier we developed this OSU03012 targeting PDK-1 so with this in mind we further designed the drug that’s targeting that—another site of the Akt which is PDK-2 site. This is mediated by this—this integrin-linked kinase, ILK.

This kinase is unique because not only it targets Akt but it also has a series of downstream effects associated with the metastatic phenotype of prostate cancer and also related to the ALDH hydrogenase prostate population through the notch-1 regulation. So we were able to show that this drug is already bioavailable and at 25 mg and 15 mg it’s able to suppress the tumor growth and more importantly with the ALDH positive subpopulation, it could suppress the viability of the spheroid formation at the micro-molar—micro-molar concentration as shown here. So this is the—our approach with targeting this aggressive phenotype.

With regard to the—the delay of the onset of tumor re-genesis, we had earlier success with our HDAC inhibitor, so we used the TRAMP model to show that because the—this transgenic mouse model by Dr. Greenburg successfully recapitulated the progression of the tumor—prostate tumor from the PIN stage all the way to poorly differentiated adenocarcinoma within a short time frame. So our goal is to—to see whether we are able to block this tumor progression by starting the therapy at an early stage of PIN, so the treatment started at 6 weeks using the diet administration at the—oral dose about 25 mg per kilogram as shown here in the table here, the drug treated group the—the prostate disease is aggressive at the PIN-stage or shift the tumor re-genesis to this adeno—adeno marker stage without going to the poorly differentiated stage. So this is very encouraging to us that we are able to show by using an epigenetic medicine, we are able to block the tumor re-genesis.

Of course the—the—the mechanism underlying this anti-tumor effect is highly complicated, and it’s mainly due to the epigenetic regulation of different tumor suppressor genes. So the lesson we learned is that by using a single targeted agent, sometimes it is very difficult to block the tumor re-genesis due to the heterogeneity of molecular defect. So we turned our attention to a fundamental character of cancer cells which is the Walberg effect. Walberg effect basically there’s a shift in energy utilization from mitochondrial dependent process to anaerobic glycolysis. That is for the—for the cancer cells they uptake glucose at the rate much higher than that of normal cells. And this principle has been used for the—for the PET scan using the fluorinated deoxyglucose and some of the earlier examples has shown that either by dietary energy restriction or chemical-induced energy restriction, there’s a chemo-preventive effect. And of course, the problem with the dietary energy restriction is not—it is not practical because you have to reduce the energy uptake up to 30% which is—I don’t think we can do that day after day.

Also the problem with some of the—the chemical restrictions, energy restriction biomimetic agent like the oxy-glucose or the resveratrol, they have low potency, so to overcome this we’ve developed two kinds of agents. One is AMP activator and the other one is the so-called energy restricted biomimetic agent, and these two compounds are currently undergoing preclinical development and I will use this ERMA, energy restriction-mimetic agents CG-12 and CG-5 as examples.

Well in the past decade there has been an increasing interest in the PPAR gamma-agonist, the thiazolidinedione family of the PPAR gamma-agonist like [inaudible] because their impact on tumor effect in terms of suppressing the expression of PSA, suppressing the effect of cyclin D1 at high doses. And people always relate this to PPAR gamma-activation. And we proved that—we obtained evidence that actually this is by mimicking energy restriction by blocking the uptake of glucose causing an energy restriction then treating [inaudible] about chemical mechanism that led into this effect. So by using this as a basis, we do the structure modification of one of these PPAR gamma-agonist thiazolidinedione and then come up with this CG-12. CG-12 our prototype compound is spread about 50 times higher potency than resveratrol and 1,000-times more higher potency than 2DG.

More importantly this is non-toxic to the normal epithelial cells. Keep in mind that normal epithelial cells and other normal cells, they can use another energy source instead of glucose to produce ATP. And of course people always think well if you restrict energy you deplete ATP and then cells die. But we learned that this is not as simple because there’s a cascade of biochemical mechanisms and we are still learning. That’s leading to the down regulation of many oncogenic protease that I skipped to and SP-1, leading to the down regulation of signaling pathway, leading to the down regulation of IGF-1 signaling pathway so on and so forth. And so this is a very complicated mechanism and we’ll have a paper coming up—it even has epigenetic effects. It can regulate the histone modification and causing the reactivation of the—of the tumor suppressor genes.

So by using this we are currently using this in our trend model and we just completed the first leg of the experiment that is from the early stage PIN to the late stage PIN, so to see whether we can slow down the—the progression of PIN. And we just—actually I just got the data on Wednesday so this is pretty—pretty fresh data. So by monitoring the weight of this—later prostate because anatomy of the mouse prostate is different from human prostate; this region mimics—resembles the area of the human prostate that causes prostate cancer. As you can see here, after the oral administration for a few weeks, it can reduce the weight as compared to the—to this control diet. So this showed that it has an effect, so of course this is pathological data that’s still pending, so it’s very encouraging news that we are able to use this energy restricting biomimetic agent to slow down the progression of the PIN. So up to this point, you know, I have given you a lot of data about well, you know energy restriction and kinase signaling pathways and so on and so forth. Many of you in the consumer group may think that well, can you say something easier for you to understand. Right; so this is—you will say give us some take-home message.

So the next topic I’m going to talk about is Vitamin E. And what of course many of us are taking Vitamin E daily as supplements. And there was discouraging news a year ago that in a SELECT trial, Vitamin E did not show chemopreventive effect. Keep in mind that in this SELECT trial alpha-tocopherol was used and there are different forms of Vitamin E like gamma- tocopherol proved to be more potent than that of—than the other form.

The conventional wisdom is that well, they are antioxidants, right. We—because of anti-oxidation it has chemopreventive effects. But it doesn’t make sense why the—the gamma form has more—higher potency than alpha form. Well, an anti-tumor effect which is often neglected when we talk about the effect of Vitamin E, its effect under Akt; I just mentioned about the term Akt, which is the evil empire in cancer cells, it has a selective effect—at very high doses. Keep in mind we have to achieve about 500—500 micro-molar also to cross the selective dephosphorylation of Akt at this—this specific site—ser473 site.

This dephosphorylation is highly specific so you may ask, well what’s happened to this? It took us for a while to figure out. Well if you treat LNCap cells, the prostate cancer cell—we talked about it—at very high doses, 500 micro-molar you’ll see a tremendous effect on Akt distribution. All of the sudden Akt treating and controlled, this is readily—even distributed across the cell, but once you treat a—the cell with alpha tocopheral and gamma tocophorol you see the Akt become membrane bound.

This is contradictory to what we learned in the bio-chemistry textbooks because Akt, membrane recruitment represents a—activation process. But in this case to make a story short, we found out treatment of this—of cells with Vitamin E—different forms, it also caused the membrane recruitment of another protein, which is tumor suppressor protein called PHLPP. This is a protein phosphatase that’s specific for Akt then it calls for the ser473 site. You can see that again it will cause the membrane recruitment and we have shown that it will call immuno-precipitate, they colocalized. So we—we provide a paradigm shift about the mode of action of Vitamin E either alpha or gamma tocopherol. Once they’re taken up by cells, it’s served as Akt recruiting molecule through the—through the PH domain. And this is mimicked—actually of PIP3, the PI3K pathway by activation process. But it is different because for the tocopherols, it will recruit another PH domain PS or PP causing the dephosphorylation in contrast to this bio-activation process leading to Akt phosphorylation, this treatment causing the dephosphorylation.

This is with low—very low potency. We talk about you know almost mini-molar which is therapeutic unattainable. So that’s why the low potency of Vitamin E cannot be effective in terms of chemo-prevention. So with this in mind, of course, we identified the binding site on PH domain and then do the structural modification and hopefully we can create a super Vitamin E that has higher anti-tumor effect that can be used in another clinical trial. So by going through this very briefly, I give you some examples about the experiment we are working on in our lab and of course this is through the funding of DoD and hopefully we can continue this funding and let’s work together to fight prostate cancer. And last on the list, I would like to—to thank all the—the previous and present members who make the work possible. Thank you so much.