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2010-07-14 Li Tang PhD Bladder Cancer Survival: The Role of Broccoli and Cruciferous Vegetables

An Interview with Li Tang, PhD

KIRK HAMILTON: Hi, my name is Kirk Hamilton, your host of Staying Healthy Today, and our message is simple: To provide you credible usable health information from our interviews and our educational resources to help you Stay and Be Well in the busy modern world. Please take a few moments before or after listening to this interview to browse through the Prescription2000.com website, the home of Staying Healthy Today Radio, for our free educational services.

Today's show topic is "Diet And Cancer Prevention And Treatment With An Emphasis On Cruciferous Vegetables And How They Modify Bladder Cancer Survival." Our guest today is Dr. Li Tang from the Department of Cancer Prevention and Control at the Roswell Park Cancer Institute in Buffalo, New York. Recently Dr. Tang co-authored an article entitled "Intake of Cruciferous Vegetables Modifies Bladder Cancer Survival" in the journal Cancer Epidemiology, Biomarkers & Prevention.

Welcome Dr. Tang. Thanks so much for coming on the show today.

DR. LI TANG: It's my pleasure.

KIRK HAMILTON: So tell me a little about your background and where you went to school as far as your PhD and then where you are now and how you got to the Roswell Cancer Institute.

DR. LI TANG: I had MD training in China then got enrolled into the University of Arizona for a master's degree in the major of nutritional science. Because I had experience working with cancer patients and I had training in the nutritional science, so this is why it made me interested in working with cancer prevention. So I moved to New York state working with Dr. Yuesheng Zhang in the Program of Cancer Prevention and Pathology. I received my PhD degree in this area in 2006 and started working in nutritional epidemiology.

KIRK HAMILTON: What got you most interested in just diet and cancer? Where there any personal experiences?

DR. LI TANG: I don't think it's personal experience but because I worked in the hospital with cancer patients, so I know the importance of the prevention. And also I was interested in the nutrition and the dietary factors and I have experience in this area. Most importantly, because I work in the lab using the cell culture model and animal models working on the dietary factors in cancer prevention. So personally I believe that the dietary factors will have some impact on cancer, so this is why I am interested in this field.

KIRK HAMILTON: Do you believe that a majority of cancers can be prevented by diet or what would you say?

DR. LI TANG: I think it is likely if you only are dependent on the diet that may not work because this whole carcinogensis process is a very complicated process. Nutrition is only a part of the story and if you're exposed to overwhelming carcinogens or other bad factors, if you only depend on the dietary factors they are not going to work and this is not a magic bullet. But if you have a good lifestyle, and you take good food, take care of yourself, I think dietary factors do have some impact especially in certain cancers, or you're expose in certain areas.

KIRK HAMILTON: Well let's look at some of the dietary factors that you might think are a problem, and let's say that the developed countries or the Western countries. Can you name a few that we have problems with let's say in industrialized countries such as in United States, or for that matter, rapidly developing countries, areas such as like in China.

DR. LI TANG: I think the main problem is the component of fresh foods and vegetables in the diet is gradually decreased because everyone is busy with work and they do not have enough time to cook. They do not want to spend enough time to prepare the fresh food, so lots of people just take in the processed food. And also with the fresh vegetables and foods, you will get a wide range of phytochemicals and vitamins. If this is your only intake of supplements, I do not think you will get enough and also get that wide coverage, so this is I think the big problem.

KIRK HAMILTON: Let's talk about your study entitled the "Intake Of Cruciferous Vegetables Modifies Bladder Cancer Survival," and it was in "Cancer Epidemiology, Biomarkers & Prevention (CEBP)" in June, and you want to tell us about that study and what your findings were?

DR. LI TANG: This study actually is based on my thesis work in my PhD period. During my PhD training, I mentioned briefly I used the cell culture model and animal model to demonstrate the chemopreventive activity of isothiocyanate in the prevention of bladder cancer. This isothiocyanate is a unique phytochemical in cruciferous vegetables. We found this chemical, this phytochemical, is especially interesting in prevention of bladder cancer because it can metabolize in the human very rapidly, then be delivered to the bladder concentrated in the urine. Their (isothiocyanates) metabolites in the urine are not stable. It can be dissociated back to the free chemicals. That chemical isothiocyanate is very potent and induces apoptosis and the cell cycle arrests, so they will stop cancer cell growth. But the most important fact for this phytochemical, isothiocyanates, is that it has strong phase II enzyme induction activity, so this can modulate carcinogen metabolism, facilitating carcinogen excretion in the human body. And I think that is the most protective factor of isothiocyanates.

KIRK HAMILTON: The iso - cyo - cyanate -

DR. LI TANG: Isothiocyanate.

KIRK HAMILTON: Yeah - isothiocyanates - thank you - which are in the cruciferous vegetables, this product gets excreted in the urine and that increases apoptosis, number one, and also increase phase II enzymes which also can inhibit the cancer, correct?

DR. LI TANG: Yes.

KIRK HAMILTON: Alright. So that's part of the benefit. Now tell us about your study because there was an interesting finding about broccoli in there.

DR. LI TANG: Actually when we talk about this study, we need to talk about the first study. This study was published in the CEBP journal in 2008 I think (Cancer Epidemiol Biomarkers Prev. 2008 Apr;17(4):938-44). We also looked at the cruciferous vegetable intake in relation to bladder cancer risk. We found the intake of cruciferous vegetables including broccoli, cauliflower and cabbage were all inversely related to bladder cancer risk, but interestingly, it was only raw cruciferous vegetables that correlated with reducing the risk of bladder cancer. So based on that study and also based on our animal model study, we found isothiocyanate can inhibit bladder cancer development in animal models, so we used the same cancer population. We looked at the tumor registry information and their medical information. We followed them up to I think a minimum of nine years. We had this follow-up data so we looked at whether this vegetable intake also influences their survival. This is the result we published in this year's CEBP. We found broccoli, especially raw broccoli, strongly correlated with improved bladder cancer survival including the overall survival and also bladder cancer specific survival.

KIRK HAMILTON: That's interesting. So what would you say would be a way to prepare broccoli aside from raw that would be protective of the isothiocyanates? For example steaming? A quick stir-fry? What would you give as suggestions to the average person out there who hears in, you know some kind of magazine, that bladder cancer survival is improved by broccoli?

DR. LI TANG: I think the best method to take (eat) this broccoli, I think is raw broccoli because this isothiocyanate occurs in the vegetable as a precursor glucosinolate. This precursor needs an enzyme called myrosinase to catalyze this reaction to release isothiocyanate. This enzyme myrosinase also exists in the vegetable itself but the cooking temperature can inactivate this enzyme. So this is why we want - we would like to take the raw vegetables.

KIRK HAMILTON: So from here, you've given us some, you know, the practical eat more cruciferous vegetables. Now might that include cauliflower as well? Can we make that assumption in cabbage, or can we?

DR. LI TANG: In all previous studies, we did find all these three vegetables because, we only have raw cruciferous vegetable intake data from the broccoli, cauliflower and cabbage. These three are the most commonly consumed cruciferous vegetables in the USA, so we only have these three vegetables raw data. But (for) the other vegetables we also collected data, but that is like the whole intake. We do not distinguish between raw and cooked. But in our previous paper we found all these three vegetables correlated with reduced risk. But in this survival paper we only found the raw broccoli correlated with improved survival. We don't know exactly why because the amount of different types of cruciferous vegetables, their isothiocyanate type and also their isothiocyanate amount is different. So maybe these different vegetables may have different preferences in certain cancers, but I think with this result we cannot draw this conclusion at this moment. We need to have some animal data to support why this certain isothiocyanate has a certain effect in certain cancers. This needs to be done in the future.

KIRK HAMILTON: Well it seems still like a good thing to eat some broccoli and cruciferous vegetables. Do you have any other comments you'd like to make on cancer prevention with diet that you've learned or directions you're going with your research?

DR. LI TANG: My direction is to go follow on this study. We want definitely, we want to because this, as you said, is an interesting finding. We are also interested in this study. We have already the cell culture model data. We also have the animal model data. But for the human study, our study was with the relatively small sample size and also it is only one study. This is the first study published in this area so definitely we need more studies to prove this is a true finding, not only a chance finding. So we are planning to do a prospective study to recruit bladder cancer patients that are diagnosed with superficial bladder cancer. So in this part of cancer patients we want to know whether their intake of vegetables can improve their bladder cancer recurrence and also improve their survival. Because for the bladder cancer patient, especially for the cancer patient with what's called superficial bladder cancer, they are easy to be treated but they will have the high risk of recurrence. We think this is a good target period to reduce the recurrence so we want to know whether cruciferous vegetables have a special role in this period of time. This is our future project.

KIRK HAMILTON: And you will be looking at whether it's raw or cooked obviously as a factor?

DR. LI TANG: Yes, definitely.

KIRK HAMILTON: Okay, well that sounds good.

Dr. Tang, I want to thank you so much for being on the show today. This interview was informative. And for taking the time out I know you are busy, and I know it's hot there but hopefully it's evening time and it will be cooling down.

DR. LI TANG: Thank you.

KIRK HAMILTON: Alright.

DR. LI TANG: And thank you for giving me this opportunity. I just hope everything goes right.

KIRK HAMILTON: No, it's perfect. Thank you so much.

DR. LI TANG: Thank you.

KIRK HAMILTON: And we'll talk to you soon. And I want to thank you, the audience, for listening to this edition of Staying Health Today Radio. And until next time, Stay and Be Well.

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