Tuesday 14 June 2011

How To Read A Cancer Paper - Part 1

By Pan Pantziarka

Intro – Why Write This?
Be prepared for a shock when you first start reading the literature on cancer. When you first dip your toe in the waters of Pubmed or other source you'll be struck by the vast number of papers that show how cancer cells are wiped out by this, that or other treatment. Whether it be plant polyphenols like curcumin or quercetin, or vitamins like C or D3, or medicinal mushrooms like Ganoderma Lucidum or... The list is endless, and so are the papers. Hundreds of them, in page after page you'll see results confirmed again and again. So why is it that cancer is still a problem? Why is it that curcumin or quercetin or EGCG or any of the other natural agents and food supplements haven't cured cancer? Because, if we believe all of these papers, then it should have been cured by now, the results are that clear. The answer is complex, and it isn't down to the fact Big Pharma has killed the research or drowned the scientists or any other favourite conspiracy theory.

This guide is aimed at the scientifically literate reader who isn't a medic or a biochemist. It's aimed at those patients and families who are undertaking to read the research directly in the hope of finding something useful. It's aimed at people who are in the situation I was in after my son's diagnosis (George was diagnosed with osteosarcoma of the mandible). I wanted to find out more about the disease, but I also read up on what we could do to support his treatment. Later, after treatment failed to halt the disease, it was because we were looking at what other options we had open to us. While I've got the scientific training (a PhD in machine learning), I was reading in a new area and without a background in medicine. The aim here is to provide a helping hand to other people in a similar situation in the hope that it will help in navigating a complicated and confusing area, particularly when the stakes are so high.

In Vitro
The first thing to note is that the vast majority of papers that are published on cancer and substance X (where X is anything from a plant product to vitamins or minerals or to fancy new nano stuff or whatever) will show that substance X will kill cancer cells. These papers are invariably in vitro studies – in other words in a test tube (or petri or culture dish). Vitro means glass, so literally in vitro studies expose cancer cells in glass tubes or dishes to substance X and then they see what happens. Mostly cancer cells in test tubes are killed by all sorts of common (and not so common) substances – plant extracts, yeasts, mushrooms, herbs, minerals, fruits, berries, vegetables and more.

This is encouraging at first. It's great. I mean who could not be happy that a common substance like curcumin or vitamin C can kill cancer cells? Even better if you can find that it kills the particular type of cancer you're interested in. I mean osteosarcoma is susceptible to curcumin, quercetin, EGCG, genistein, sulforaphane and more. It's not just plant extracts. There are plenty of papers showing that commonly used non-cancer drugs, such as celecoxib, are also potent anti-osteosarcoma drugs. Osteosarcoma isn't unique here, for every type of cancer there are papers that show dozens of different substances have potent activity in the test tube.

However, there are some key things that have to be kept in mind when reading these papers. First and most obvious is that a test tube is not the same as a live body. It's not even the same as a live tumour come to that. A live tumour contains lots of different types of cells, it's surrounded by a whole supporting eco-system of cells (commonly called the tumour microenvironment or stroma), and it interacts with an immune system and is supplied with blood and nutrients. Most of these are not present for in vitro studies. What you have is pretty much a thin film of cancer cells sitting on a growth medium – which is a long way from cancer cells out in the wild.

Secondly, these carefully nurtured cancer cells are then exposed to a very closely monitored dose of the candidate substance or drug. Not only is the dose carefully calculated, the length of this exposure is carefully controlled too. Very often the substance being tested is used at such high doses and for sustained periods that it is physiologically impossible to achieve this in practice (at least without killing the patient).

Yet another issue that is relevant is which form of substance X is being tested. In the majority of cases the experiments use a purified form of the substance, often dissolved in solvent or processed in some way. Again this is a problem if you are looking for foods or nutritional supplements because of the obvious reason that you or I will have to swallow and metabolise the substance. This means that what passes out of the gut is not the same substance as that being tested in the lab. For example most in vitro studies of the anti-cancer effect of curcumin use pure curcumin rather than the metabolites that come out of our digestive system.

Finally, attention also has to be paid to the particular cell lines being used in these in vitro studies. It isn’t enough to say that a study has used breast (or prostate or osteosarcoma or whatever) cells – you need to know exactly what sub-type of the disease. And even with the right sub-type, you need to know what characteristics these cells express – what is the p53 status? Androgen or oestrogen responsiveness? Does it express cox-2 or other inflammatory markers? Does it have high or low metastatic potential? All of these are important questions, and of course you need to know some of those answers for your own disease. Why? Because it’s not uncommon to find that an in vitro study is performed against a panel of different cells lines and that there are good results for some, and poor results for others, even though all of the cell lines are breast or prostate or other type of cancer. Or, just as common, two different sets of experiments exist, performed by different teams using different cells lines and they’ll report opposite conclusions...

Unfortunately what this means is that the startling results in the test tube don’t translate to our bodies. The in vitro study tests an artificial system of cancer cells with impossibly high levels of a pure substance that we couldn’t pass out of the gut no matter how much of it we swallowed. To all intents and purposes this means that you have to take these test tube studies with a huge pinch of salt. In the test tube substance X kills cancer, but that really doesn’t mean much in the real world. At most it gives you reason to carry on looking at substance X in more detail, but that’s about it.

What's The Point?
If this is the case then why are so many in vitro studies being performed? What is the point? It’s a good question.

Firstly and most obviously in vitro studies are relatively easy to perform. Compared to doing animal or human studies in vitro studies are easy. There are no ethics committees to convince, there’s no hassle of dealing with animals (and thanks to the activities of ‘animal liberationists’ there are no major security worries either) and the results can come out quickly. For a beginning researcher or a department looking at its publication record (and probably funding applications), this is a simple way of getting published. This isn’t being cynical, scientists are people too and they’ve got other pressures to worry about as well as trying to make progress against cancer. Getting a few good papers published adds weight to a PhD thesis, it adds weight to a departmental publication record and can spark off other interesting ideas for research.

It’s also worth pointing out that there are many in the animal rights lobby who are actively working to increase the amount of in vitro work going on because it saves the lives of laboratory animals. For them saving animal lives is more important than the fact that many of the results of in vitro experiments are of academic interest only and don’t translate well to animals or humans.

This isn’t to say that all in vitro research is useless. When a relatively new substance, a rare plant extract for example or some fancy new molecule, is discovered then the research has got to start somewhere. This is a quick way of knowing whether it’s worth exploring in any more depth or not. And when you want to elucidate how particular pathways interact, or you want to understand what proteins are expressed in specific circumstances – in other words you are interested in detailed biochemical analyses – then in vitro work is ideal. But if your aim is to see if substance X kills cancer Y at dose Z then in vitro studies are so far removed from what happens inside people that the results are barely relevant.

There are those who are working hard at addressing some of the pit-falls that I’ve outlined previously. For example there are groups of researchers working on producing tumour spheroids under glass – in other words they want to produce 3-dimensional tumours in vitro, making them more like the real thing. There are also experiments where the metabolites of curcumin or other substances are used and not just the pure raw material. And of course there are those in vitro studies where the researchers go out of their way to only use physiologically achievable doses. This is all to the good, but as a reader of that research you have to be on the look out for these. Another strand of activity is in silico studies, where researchers use fancy software to test how different molecules connect with each other – again useful as a first step but a million miles from the insides of a living, breathing person.

So, having convinced you of the many problems with in vitro research, you’ll be wanting to get stuck into all of that solid research using in vivo models. In vivo means in a living being – which most often means rats or mice when it comes to the bulk of cancer research. More of that in the next article.

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