Dr. Kucuk presented at the 26th International Prostate Cancer Update on Thursday, January 21, 2016, on “Soy Isoflavones in Prostate Cancer Prevention, Treatment and Survivorship Research.”


Keywords: prostrate cancer, soy isoflavones, genistein, chemotherapy

How to cite: Kucuk, Omer. “Soy Isoflavones in Prostate Cancer Prevention, Treatment and Survivorship Research.” Grand Rounds in Urology. January 21, 2016. Aug 2021. https://grandroundsinurology.com/soy-isoflavones-prostate-cancer-prevention.


Soy Isoflavones in Prostate Cancer Prevention, Treatment and Survivorship Research

Today I’m going to talk about soy.

Prostate cancer incidence and mortality has great variations around the world. The incidence of mortality are very low in certain regions such as Southeast Asia, China, Japan, Korea, and the Mediterranean region, but it’s very high in North America, and Northern Europe.

There have been epidemiologic studies suggesting that maybe dietary factors may be important. For example in the Mediterranean high tomato consumption, in Southeast Asia, soy consumption, and India which is another low rate area, curcumin might be important factors in the prevention of disease.

Soy isoflavones have been shown in many epidemiologic studies to have an inverse association between the consumption of soy and prostate cancer risk, as well as other cancers. And genistein and daidzein are the two primary components as isoflavones in the soy, and they have been postulated to be the main preventive factors in soy. But there are other important molecules in soy that may also have preventative effects. Genistein is the prototype and has been the most studied agents in soy, and it has activity against a variety of cancer cell lines in culture, in animal models and also in clinical trials. It has shown promising activity.

Here’s soy isoflavones, genistein. It has similarities to estradiol. It binds to estrogen receptor, just like tamoxifen is more like a selective estrogen receptor modulator, more similar to tamoxifen than estradiol.

Soy isoflavones in addition to their effects on estrogen receptor beta that they have multiple other effects, for example, they increase osteoprotegerin levels, they decrease RANK ligand, they can also help vitamin D metabolism, and decrease inflammation.

These have all been published by our group as well as other groups. For example, if you at the mechanisms, genistein has been found to inhibit the growth of prostate cancer cells in vitro, and it downregulates molecules that are important in cancer cell growth.

It also down regulates molecules that are important in cancer metastasis, it inactivate Akt and NF-kB.

This is just an example of in the PC3 castration resistant prostate cancer cells, the effect of genistein decreasing cell growth.

We have also discovered that genistein not only increases the death of prostate cancer cells, but it can also affect chemotherapy. For example, here docetaxel and genistein alone killing prostate cancer cells. These are castration resistant. But the combination of genistein and docetaxel is much more effective than either one alone. So there may be a role adding genistein or soy isoflavones during chemotherapy.

This also is true for inhibition of cell growth. We thought this might be related to effects of isoflavones on NF-kappaB activity because when prostate cancer cells are exposed to chemotherapy, they upregulate NF-kappaB which confers survival advantage and makes the cells resistant to chemotherapy, but we could prevent that by adding genistein even though chemotherapy can upregulate NF-kappaB in the cancer cells when genistein is used together with chemotherapy, there is no upregulation of NF-kappaB. That may explain why genistein given together with chemotherapy may increase the efficacy of chemotherapy. Now this does not happen with normal cells. Of course if you give genistein during chemotherapy, you don’t want to sensitize the normal cells, you just want to sensitize cancer cells.

We looked at normal human marrow cells to see if their sensitivity to chemotherapy is affected with soy. Actually soy has some preventative effects. The curve went to the right when we used genistein in these cells. These are normal human marrow cells. When they’re exposed to chemotherapy, it takes more chemotherapy to kill them in the presence of genistein. It increases sensitivity of cancer cells but protects the normal cells from chemotherapy. It could have a role being used during chemotherapy. Of course we need clinical trials.

This is kind of a summary of the hypothesis genistein by inhibiting NF-kappaB, it also inhibits downstream molecules that are important in cell growth and metastasis and this way it may help improve the efficacy of chemotherapy.

Now we have also shown the same thing in an animal model. The previous slides were in vitro tests, and in an animal model of bone metastasis, we have also shown that giving animals soy isoflavones will decrease the growth of tumor. And will the controlled animal, you can see bone metastasis destroying the bone, but in the animal that received soy, there is no destruction of the bone, and the tumors are much smaller.

In the same animal model we have also looked at the combination of genistein and Taxotere or docetaxel chemotherapy. As you can see, just like we saw in vitro in the animal model to a combination of genistein together with docetaxel, it’s much better than genistein or docetaxel alone.

One of the side effects of chemotherapy, it reduces osteoprotegerin levels. Osteoprotegerin is very for bone health. Obviously you don’t want to reduce that, especially in prostate cancer patients, and they develop osteoporosis due to hormone therapy, and the last thing you want is to reduce osteoprotegerin. That’s what happens when you give docetaxel or Taxotere to prostate cancer patients, but if you give genistein, you actually increase osteoprotegerin levels. And you can totally prevent the lowering of osteoprotegerin with docetaxel when you add genistein together with docetaxel.

We’ve also looked at the RANK ligand. We found that genistein decreases RANK ligand and docetaxel increases it. Again, here is a paradoxical situation, when you give docetaxel to patients, obviously you’re killing prostate cancer cells, but at the same time you’re increasing the RANK ligand levels, which is not something you want because we have a drug that we use in prostate cancer patients with bone metastasis, denosumab or Xgeva, that we frequently give to these patients because their RANK ligands are activated and they develop osteoporosis and their bone metastasis may increase. But with soy we can actually inhibit that RANK ligand and decrease the formation of osteoclast which destroys the bone.

We found the same thing with matrix metalloproteinases. When you give Taxotere, it increases matrix metalloproteinases, so another paradoxical situation. You’re giving chemotherapy to kill the cancer cells, you’re decreasing the cancer, but at the same time, you may be doing hard because docetaxel increases RANK ligand and MMP 9 levels and may promote cancer metastasis. So patients may actually develop more aggressive disease while they’re getting treatment. But you can prevent that again with soy.

And also in the cell invasion assay, that when soy is used together with chemotherapy, you inhibit invasion much better than the two agents used alone.

We also looked at gene expression profile. In the same model bone metastasis model, prostate cancer cells have very high levels of matrix metalloproteinases, but if you use genistein or soy isoflavones, you can see that there’s decreased expression of matrix metalloproteinases. Many genes are upregulated or downregulated with genistein, and there are further studies looking at that. If you summarize most genes that are involved in cell growth, are downregulated by soy. Genes that are involved in apoptosis that are upregulated, NF-kappaB is inhibited, osteoprotegerin is increased.

We also did a clinical trial, which was published, actually Singh was the first author of this one when she was at main state with us. Patients who are hormone sensitive and hormone refractory patients, when their PSAs were going up, these are non-metastatic patients, biochemical failure, PSAs were going up. When we put them in soy isoflavones, you can see that we decreased the rate of the growth, or decreased the rate of the increase in the PSA levels. Actually we are not reducing the PSA, but we are slowing down the disease which may… these patients were on soy isoflavones for six months. These are the patients who are hormone refractory. These would be the patients that you would be considering chemotherapy, and you can see that for six months, they did fine without chemotherapy.

We also looked at radiation therapy. This is an animal model of prostate cancer. When you give radiation therapy, obviously you make tumors much smaller. But if you give radiation together with genistein, tumors are even more better treated, with decreased tumor size with the combination, which tells us that soy not only increases the sensitivity to Taxotere but it also increases the sensitivity of cancer cells to radiation therapy.

We also did a small clinical trial using soy isoflavones in patients receiving radiation therapy, and this was just to look at quality of life and symptoms because obviously to show efficacy you have to wait 10, 15 years.

In these patients, these are the baseline soy group and this was a placebo controlled randomized study. These are the PSA decrease in the soy group, and the placebo group we found that these are very small numbers, you can see only 13 patients in each group.

There was some decrease in the GI toxicity from radiation therapy. And there were also some improvements in erectile function. So this is a small pilot study which needs to be confirmed with larger studies.

We also looked at DNA methylation, previous speaker already brought up the DNA methylation which is very important in prostate cancer development. The researchers have shown that DNA methylation can be reversed by soy. First to report C. S. Yang from Rutgers reported that way back in 2005. And then Rajvir Dahiya from UCSC also reported the same thing that genistein can decrease methylation and affect the gene expression profile.

When I came to Emory, we also looked at some prostate cancer patients. We found increased methylation of the Wnt pathway genes that are shown here.

And when we used genistein in cell lines, these are two different cell lines, these are epithelial type and mesenchymal type prostate cancer cell lines. When we exposed then to genistein you can see significant changes in gene expression in these cells.

And genistein upregulated the genes that are involved in cell cycle response, the DNA damage shown here including BRCA1 gene, and it downregulated genes that are involved in the TNF NF-KappaB pathway.

We also looked at acetylation. It may not be just methylation but acetylation may also be important when histone acetylation happens that has the similar effect as DNA demethylation.

And we found that there is increased histone acetylation with genistein, and histone acetyl transferase activities increased in prostate cancer cells exposed to genistein which can explain that.

We looked at other histone deacetylase inhibiters like vorinostat. Vorinostat, genistein in two different cell lines. You can see that genistein is very effective in decreasing cell proliferation and when combined with Vorinostat the effect is even higher. It’s almost as good as azacytidine which is a demethylating agent plus vorinostat histone deacetylase inhibitor. It also showed the same thing genistein, vorinostat, and the combination is much better in killing the cancer cells so it synergizes with genistein and histone deacetylase inhibitor.

We looked at gene expression profile using the combination of genistein with vorinostat. You can see huge changes, 10(-3), 10(-14), changing in gene expression profiles when the genistein and vorinostat are used together.

Another thing in prostate cancer patients we worry about the adverse effects on androgen depravations such as cardiovascular disease, metabolic syndrome. There is a possibility genistein may also be helpful. In that situation genistein has been shown to have endurance enhancing activities, which may be related to PPAR gamma and AMPK.

Genistein has been shown to have both PPAR gamma and AMPK agonist activities. In a randomized placebo-controlled clinical trial, genistein plus calcium and vitamin D in women, postmenopausal women, has been shown to improve glycemic control and decrease cardiovascular risk markers.

And these are things on the market. I’m just showing this because the investigators said that study used these products and they gave only 54 mg of genistein which is easily achievable.

In animal models, it not only increased insulin sensitivity, but also memory. Recently you’ve seen papers in the media saying that androgen deprivation can lead to Alzheimer’s disease. A lot of patients will be asking you about that, but there is a possibility that soy products may improve memory, may have a role in prevention of Alzheimer’s.

Researchers at the University of Alabama in Birmingham actually did some studies in monkeys. When they looked at monkey brain, genistein decreased the phosphorylation of Alzheimer’s disease related proteins and by inhibiting the high phosphorylation of these proteins, genistein can stabilize the microtubules in the brain which may explain the improved cognitive function in these patients.

This was also shown in a double-blind, randomized placebo-controlled study in postmenopausal women given isoflavones, it improved their cognitive function.

We have also done a small clinical trial in children and we found that giving genistein during chemotherapy resulted in less myelosuppression, less mucositis and infections so there may be a role adding genistein during hormone therapy, chemotherapy, and radiation therapy.

Genistein will lend itself very well to survivorship studies. It has antioxidant effects, anti-inflammatory, it causes DNA demethylation, histone acetylation, inhibits multitude of molecules, enhances chemotherapy and radiation, reduces toxicities of chemoradiation, it also potentiates immune function which I didn’t show.

And finally, in the final slide, in survivorship research, it could be used in multitudes of areas like cognitive function, cardiac toxicity, reducing myelosuppression, pulmonary toxicity, neurotoxicity, and these are all the studies that remains to be done.

So, we’re in the localized disease part of the session, of the meeting. I was charged with talking about accurate staging with radiology. I’m going to focus more on the imaging of metastatic disease, so we do it correctly, so that when we treat localized disease we’re sure it’s really just localized disease.

I think there are a couple questions that are important to this. So, the questions seem to become what imaging tools are available? And I think this is really confusing because there have been a lot of developments in radiology nuclear medicine with regards to the imaging tools currently available. The other question is, when do I use them?

This is just a table from the RADAR article in 2015 that just goes over the different recommendations from all the various groups; AUA, ACR, Prostate Cancer Organ Group, and there’s a lot of sort of differences between the different recommendations among all these different societies. I think that creates a lot of confusion.

So, for today’s talk I’m really going to talk about the past, the present, and the future. Another goal of mine is to sort of filter the signal from the noise. I think one of the frustrating parts of prostate cancer imaging is everyone reads the journals and you see all these different letters attached to either FAT and C11 or OAT. I think that creates a lot of confusion. So, today I’m just going to filter it down to the ones that I think are important, and I think are going to change the way we practice in the near future.

First we’re going to talk about the first generation imaging modality. Yesterday Dr. Crawford had shared a slide about the first article talking about bone scintigraphy, and that was from 1972. So, fast forward to 2016 and we’re still using this as sort of our standard of care imaging when it comes to bones. You see the images here, just typical – – images. We acquire them anterior and posterior views. We can acquire lateral views and do spect and other things as needed.

It’s served us really well, but I would argue there are better things out there, and I think we need to explore those different areas.

Prostascint; something that’s really fallen out of favor in the past few years. One of the big problems with prostascint is it binds with internal epitope, a PSMA, which often detects the chronic disease and has decreased sensitivity. The performance of the exam is a little more difficult; it occurs over multiple days.

That being said, there are still some groups out there that are having some success with this, and I know Dr. Keane at MUSC is using this and is happy with the performance of this, but I think overall, the NCCN guidelines also dropped this from their recommendations as well.

Sodium fluoride; we think of this in a lot of ways as a novel imaging tool, but it’s really not novel. It’s actually been around longer than tc-99 diphosphonates. But there’s been this resurgence because PET CT technologies are much more available. I think it’s a powerful tool. When we first talked about sodium fluoride PET CT five years ago at this meeting, I think it’s really helped a lot of practices. If you haven’t started doing this, I encourage you to look into this.

So, just to show the power of sodium fluoride, we had this recent case, so this was May 18th, this year, Gleason 4+5, PSA was 28.73, 28.7. On this typical, standard bone scan, we didn’t see any bone meets. We just called it negative; no syndographic evidence of metastatic disease, next case.

All right, so then fast forward to July 19th, a couple months later. They sent CT to look for soft tissue disease. They saw this subtle lucency here, which it’s pretty non-specific. We see these lucencies often; if we started calling these mets I think we would over-call a lot of disease. Since it’s prostate cancer, yes, it could be lytic, but we typically sort of prefer to see sclerotic disease, as it’s more common.

A couple weeks later the PSA shot up to 118.4. Dr. Crawford saw the patient, knew something was really wrong. Despite a negative bone scan from a couple months prior, he went ahead and ordered a sodium chloride PET CT. If you look at this map image here, you see this marked burden of osseous metastatic disease throughout predominantly the axial, but also the proximal appendicular skeleton. This was probably one of the most dramatic cases I’ve ever seen in that short of an interval, between a planar bone scan and sodium fluoride PET CT.

If you look at the cross-sectional images you see intense uptake in these bones, and on the CT it actually looks completely normal. There’s not sclerotic disease, but again, yeah, the PSA went up, but I would argue had we done the sodium fluoride up front, we probably would have detected the disease, or a lesion or two, in those cases. But again, this is important, because clearly this isn’t localized disease anymore that we’re dealing with.

This was–I forget what therapy they received, but after some therapy the bone lesions on CT became sclerotic. So, this is probably just a case of lytic disease that was missed. There have been papers talking about how even though sodium fluoride detects bone changes, it still is more sensitive to lytic disease, and has actually had success in imagine RNASEL cancers too, which often planar bone scans miss. So, it’s a great tool.

GUSCO recently had this past meeting a discussion about will sodium fluoride PET CT replace bone scintigraphy. That’s something we also discussed in the Arizona meeting a couple years ago. There’s a good review on that, and I believe it’s on Urotoday.com that sort of outlines the discussion of that meeting with regard to sodium fluoride PET CT.

This is an update from CMS’s decision December 15th of just a month ago. CMS determined that they were not going to pay for sodium fluoride PET CT, in part because there wasn’t enough data. There was data that showed there was change in patient management, but CMS wanted to see more data with regards to outcomes.

They want to see changes that lead to more appropriate palliative care or more appropriate curative care. Improved quality of life or improved survival. This was very disappointing, but that being said, CMS agreed to extend the National Oncologic PET Registry Program for another two years for sodium fluoride PET CT, so if you haven’t done it right now, you can go ahead, sign up, and again, CMS will cover this for the next two years at least, and then more data will be collected and hopefully in a year or two we could resubmit for reimbursement or approval.

All right, so we’re going to move onto the second generation radiopharmaceuticals, and this is when it becomes a little more novel. I’m sure all of you have heard about C-11 choline; you’ve heard about it for the past couple years, but we’ve been very frustrated with C-11 choline because we keep hearing about it but we can never order it.

Even at the University of Colorado we looked into starting our own C-11 choline program, but the costs were too high. It would take too long to get it available, and in the end we just decided not to. I think C-11 is great. The data there, a lot of it coming out of the Mayo Clinic in Europe has been really promising, but again, the idea of access, the problem with access is really what’s killing this radiopharmaceutical.

Because, again, the reason is C-11, carbon-11 only has a 20-minute half-life and it requires a medical cyclotron to be onsite if you’re going to do these exams, and a medical cyclotron is a very expensive and complicated endeavor.

So, F-ACBC, amino acid analog, this is very promising. I think this is why we’re no longer going to talk about C-11 choline in the near future. The key to F-ACBC is its F-18. It has a half-life of two hours as opposed to 20 minutes. This makes commercialization of this radiopharmaceutical much more feasible than C-11 choline. The question is how this F-ACBC compares to C-11 choline.

The beauty of both of these agents–and there are other agents out there like C-11 acetate that are good as well, but I’m just going to focus on these two–the beauty of these two is it detects disease in bone and soft tissues, so instead of ordering a CT scan and a bone scan separately, you could actually just get this one scan and detect disease in both sites.

So, this was a recent paper published in Clinical Nuclear Medicine, August 2015, that compared F-ACBC versus choline. This came out of Italy. Prospective study with 50 patients. They received both of these scans within one week. On a per-patient analysis, the F-ACBC and the C-11 choline were negative on both scans in 33 of the 50 patients. The F-ACBC was positive and choline was negative in six of those cases.

F-ACBC detected disease in six patients that choline did not, and then they were both positive in 11 and F-ACBC was never negative when choline was positive, so the F-ACBC performed better than the choline in that study. This is on a per-lesion basis, and again, F-ACBC detected more lesions in more patients than C-11 choline.

This is just some example images from that paper. You see this aortic caval lymph node, it’s sub-centimeter. If you were just getting a CT scan with IB contrast no one would call this metastatic disease, but when you add the radiopharmaceutical to it, there was a little bit of uptake there. They called it metastatic disease, and on choline there was no activity localizing to that lymph node.

This was a bone lesion; I don’t think this is the greatest example, but this is what they published. It showed increased uptake in that right iliac bone compared to C-11 choline, which allowed them to call that positive as opposed to negative.

Based on PSA levels, F-ACBC performed better than C-11 choline at PSA levels less than 1.0, 1.0-2.0, 2.0-3.0, and greater than 3.0. I wouldn’t take the detective rates at PSA levels because the sample size was too small, but at all the different levels, F-ACBC did perform better than the C-11 choline.

This is the exciting part of F-ACBC which is relatively new. It’s being commercialized by Blue Earth Diagnostic, and they’ve actually entered into contracts with PETNet, which is a subsidiary of Siemens, so they have the infrastructure in place to distribute this radiopharmaceutical across the country, and pretty much across the world as well.

There’s this little blurb that talks about how this was just accepted for priority review at the FDA, and this was dated December 2, 2015. Hopefully–I don’t know how long it will take–but maybe in 6-12 months we’ll actually see the approval of this for use.

Third generation; this is when more long-term future–it’s the exciting stuff but I wouldn’t hold our breath at the moment. With that being said, it’s not too far away. The PSA agents are the real exciting agents that are going to change the way we image patients as well. Gallium 68 is something that you’ve all probably heard about. The beauty of Gallium 68 is its sensitivity at low PSA values ahs been really good. If you look at PSA values less than 0.5, it showed 58% detection rate, which is better than all the other prior radiopharmaceuticals.

We’re going to move on to FDC FBC, which came out of Johns Hopkins. They did a recent study published in The Journal of Nuclear Medicine that looked at 13 patients, and what they found was it wasn’t as sensitive compared to–so this was looking at primary disease, not metastatic disease. Dr. Keane, this is what we were talking about last month. But, what they found was it wasn’t as sensitive compared to MRI, but the radiopharmaceutical had higher specificity for high-grade and larger tumors compared to MRI.

I think that’s really exciting because it brings up the idea of PET MRI, and I think Dr. Andriole in the discussion earlier had talked about PET MRI, and this is, I think, an ideal use of where we could combine MRI with this radiopharmaceutical for primary disease, and actually be able to detect those higher-grade tumors that will lead to more morbidity and mortality.

I think this is a game-changer, but it’s PET MRI. $4.5, 5 million for a machine, and you’re not getting reimbursed for it. So, I think there’s still a lot of questions with regards to what is the exact role of PET MRI in the future, but I think it’s very exciting and it’s an area that’s being investigated heavily.

Theranostics is another area that’s exciting. It’s the ability to image entry disease simultaneously, and that’s only possible because these PSA agents are most specific with prostate cancer.

This comes from a review article, an image provided by Dr. Peter Toikey that shows DCFBC being investigated now for the detection of metastatic disease as well, so it could be used in the primary setting and hopefully in the metastatic setting as well.

So, the question becomes when do you deploy these different radiopharmaceuticals, or when do you deploy these different imaging agents? That’s when we sort of go back to the RADAR guidelines. Dr. Crawford had organized this with Dr. Petrylak a couple years ago to really look at when we should image, and in 2015 this was actually one of the viewed or downloaded urology articles for that year.

It sort of puts patients into three different buckets; newly diagnosed patients, biochemical recurrent patients, and M0-CRPC patients, and it gives recommendations as to when you should image them. You don’t image low-risk patients, but PSA levels greater than 10, lesion scores, it should be greater than or equal to 7, or palpable disease in the biochemical recurrent patients, M0-CRPC patients.

There’s no good data out there, but amongst the group that was assembled, a multidisciplinary group, we voted as to what would be the best manner in which to image those patients. The decision was first scan them when the PSA level was greater than or equal to 2 nanogram per milliliter, and then image the second scan with a PSA equal to 5, and every doubling of the PSA thereafter based on a check of the PSA every three months.

We realize that the M0 patients were not being imaged frequently enough and we were missing more–we were detective metastatic disease too late.

We wrote another review article talking about–sort of piggybacking on the RADAR guidelines, incorporating sodium fluoride and choline into that algorithm. But, I would argue we could just sort of put F-ACBC in that algorithm once it is approved.

So, I think the two take-home messages are if you haven’t incorporated sodium fluoride PET CT, it’s available. It’s being reimbursed by CMS and I think it’s worth a shot.

Number two, let’s get excited about F-ACBC. I think we will no longer have reasons to complain about C-11 choline because we’ll have an equal, if not better, radiopharmaceutical available hopefully in the near future. Let’s image our patients more frequently, but let’s image them smarter based on how they present.