As a cancer scientist and someone interested in the ever-evolving relationship between science and the media, my eye was caught this week by the flashy headlines claiming that good-old tomatoes might just be the cure for gastric cancer. All the media fuss appears to stem from a paper accepted last week in the Journal Of Cell Physiology bearing the rather less exciting title : “Antitumoral Potential, Antioxidant Activity and Carotenoid Content of Two Southern Italy Tomato Cultivars”. As a fan of both cancer research and tomatoes, I felt the need to examine the evidence presented in the paper and whether they substantiate the Daily Mail claims.
Having read the article, it transpires that it is a very nice piece of work focusing entirely on cell line in vitro work. What this means is that the effects of the tomato extracts were tested on cells that are kept in isolated culture and grown in a dish. Cell culture is one of the most essential building blocks of cancer research and an extremely valuable tool. It uses cells that have been taken out of tumors in live patients, which are then grown in sterile culture dishes. Because getting cancer cells from live donors and “training” them to live in a cell culture dish is an extremely time-consuming and costly endeavor, scientists all over the world share the cultures they establish. Each culture that is established from a single patient is known as a cell line. Cell lines retain many of the properties of the original cancer cells, but have been modified to survive in a culture dish and have been “immortalized”, which means they have been modified to continue propagating virtually for ever. Therefore, while cell cultures are a fantastic model for studying cancer, they are not quite the same as cancer itself. A good analogy for how cell lines relate to real cancer cells is dogs against wolves. While dogs have retained most of the essential features of wolves, they are by no means the same thing! A further layer of confusion that is introduced when working with cell lines is the fact that cell lines mutate while they are kept in culture. Cancer cells are, by nature, very genomically unstable and subject to frequent mutations. To aggravate the problem, since cell lines have been immortalized they are kept in culture for decades – which means that they are replicating at a very fast pace for years and years, thus being at very high risk of accumulating mutations over time. Since cell lines are passed around among several laboratories throughout the world, scientists working with the same cell line in Cambridge, Massachusetts and in Cambridge, England might end up dealing with rather different lines that have accumulated different sets of mutations. To keep with the canine analogy, while all dogs are rather different from wolves they can also wildly differ from each other – a pug looks really rather different from a husky, or a spaniel.
In spite of all of these flaws, working with cell lines is actually a very powerful tool for scientists trying to understand how cancer works. However, because of these and other limitations cell line work is usually supplemented by other types of experiments. Crucially, all this in vitro work is complemented by in vivo work, showing complementary results in animal models such as flies or rodents, or in patients. The key idea of this type of biology is that if the same idea is shown through several different approaches and in different models it is more likely that they will be accurate. When a study is published without these complementary results, it has necessarily less impact than a study that makes a case using both in vivo and in vitro methods. In layman’s terms, results that are purely based on cell culture work are not necessarily unreliable, but must be taken with a pinch of salt. The question then becomes – why has this article been branded as a potential new cure for cancer?
The answer is obvious to anyone who has ever read a newspaper – because it’s exciting. A potential cure for a horrible form of cancer hiding out in everyone’s vegetable crisper gives us the warm, fuzzy feeling of being ultimately in control of their lives. And it makes them click on the link, or buy the paper. What’s more, it’s accessible. Everyone over the age of three knows what a tomato is – and everyone can feel like they have some form of control over the scary, faceless of monster of cancer if they can effectively fight it with a garden vegetable people grow on their balconies. What is a real shame is that in order to cover these non-news the media has missed the opportunity to cover some amazing and really promising science news. For example, an article published in Nature at around the same time has shown that a specific set of molecular signals in the tumor microenvironment (that is, the tissues in the body surrounding the tumor) can drive tumor spreading in lung cancer. This article uses cell lines, as well as cells directly taken from patients (known as primary cells), as well as studies in model organisms and samples from real lung cancer patients. In fact, this paper showcases some truly amazing images of human cancer cells as they spread. Now that scientists know about how important these molecules are in these tissues, they can start working on engineering new drugs that can directly target and block these pro-cancer signals. This represents a real, concrete hope for patients suffering with cancer today.
Perhaps the solution to impactful science not being particular glamorous to the general reader does not reside in ignoring it, but in educating the public by explaining the wonderful things that are really happening in cancer research every day. And holding off on the tomatoes until we have more solid data on what’s going on.