In 1975, Gullino and Butler at the National Cancer Institute(NCI) made perhaps the first definitive measurements of tumor cells shedding into peripheral blood. The significance of that seminal work did not reach its potential until nearly 30+ years later, primarily because the tools that could move it forward did not exist. Those tools are embodied in the CellSearch® system for detecting and characterizing Circulating Tumor Cells, a product of Veridex, a Johnson & Johnson Division now part of Janssen Diagnostics. The genesis of CellSearch® that geminated the world wide interest in Circulating Tumor Cells [CTCs] is worth recording.
In the late 1980s, at Immunicon in Philadelphia, we were doing a collaboration with Temple University hematologist Dr. Ken Mangan on purging B Lymphoma cells from marrow and blood. At Immunicon, we were using a magnetic separation system I had developed that was based on highly magnetic liquids (tagged with Mabs) that I had patented in concert with an ultra-high gradient magnetic device with two of my scientists, Youzhou Wang & Weixing Tang. We were labeling a B cell line, spiking cells into blood and seeing (by PCR) how effectively we could retrieve them. As we kept lowering the spike level, we did some calculations using Poisson statistics and realized that we would effectively have to analyze the entire product of separation to determine with any accuracy if any cells were left. Accordingly, we began looking at what we were purging rather than what might be left in the sample. To our great surprise, we found that we could repeatedly retrieve labeled cells that were spiked at the level of 1 or 2 cells per mL of sample.
In our lunch room, Youzhou, Weixing and I shared those results with Bill Cronin, a very bright pathologist that we had on staff. I asked Bill if this could be a means to track or detect cancer early on in disease. His response was – ‘possibly late in disease but there’s not much evidence of the importance or real existence of CTCs early on in disease.’ But he added ‘it might be worth a try.’
Because we were about to lose a major contract with Eastman Kodak Life Sciences’ Clinical Products Division (the division was being sold) for the development of a magnetic Immunoassay system, and even though when I shared the notion of testing for CTCs on cancer patients with a few well informed colleagues, no one thought it a good idea, I decided this new direction could be a way to salvage the company. Rich Horan, my VC partner, helped me convince my Board it was a good idea – and off we went. With our Board, we used the expression ‘rare cell’ detection, only casually mentioning ‘looking for cancer cells in blood.’
To do that we needed a resource we did not have in the company – someone who could do the tumor cell characterization, while I concentrated on the enrichment technology. Rich asserted that we needed someone who was expert in Flow Cytometry to which I immediately responded I know that person. It was Leon Terstappen who was running Flow Cytometry R&D at BD in California. I had met Leon at a recent meeting and chatted with him about some work he had done, and, I liked him. The issue now was how do you recruit someone out of sunny California who is top dog in the field, at his company and who is well paid as well, to a biotech company that’s on its third mission in 12 years and that has yet to sell a product. To my Boards’ great surprise, I managed to convince Leon this would be the opportunity of a lifetime. I had told him I would make him much more famous than he was and I would also make him rich.
With Leon on board in the first year, I was not at all successful in getting him focused on CTCs mainly because no one he knew thought it was a worthwhile venture. [One of our mutual colleagues called it a ‘fool’s errand’.] But then the immutable laws of connection changed everything. Jonathan Uhr, a prominent immunologist in Dallas made a call to Noel Warner, Director of R&D at Becton Dickinson whom I had known casually over the years and who had worked with Uhr years back. Uhr had been working on cancer dormancy for years. He was convinced that dormant cancer cells were circulating in peripheral blood and that somehow they become activated and disease reoccurs. Jon was looking to see if BD might have an interest in supporting his work. Noel remembered my interest in CTCs when I was recruiting Leon and directed Jon to Leon.
Jon Uhr’s call to Leon made him an instant convert and overnight we directed Immunicon’s effort into developing a reliable method for getting at these tumor cells. Even though Uhr’s interest was circulating dormant cells and mine CTCs, we were on the same train. With parallel efforts in Dallas analyzing bloods from newly diagnosed breast cancer patients, we, in Philadelphia, were not getting very convincing results. Fortunately, Jonathan sent Emil Racilla, his post doc, to our labs to show us what he was doing that was working. Emil who was really key to the whole effort had realized something we had not – to isolate just a few cells, one had to use extraordinarily extreme measures to keep from losing them. Any missteps and down the drain they went and as obvious as that might seem, we had not gotten it! Were it not for Emil’s insights as to how this test had to be done and Jonathan Uhr’s insights as to what this technology could do we might have gone down the drain with the cells!
There is another part of the story that is relevant. With Leon and I dedicating all our time to pushing this boulder forward, we were lucky enough to get a ‘volunteer’ who would play an important role. I managed to talk Jerry Doyle, a practicing dentist and former Ph.D. student into helping us 2 days a week. (I was counting on his 2 days stretching into a lot more, and I was right on that.) Initially his help was undefined but with the publication of the PNAS paper on the horizon and the potential of what we were onto – that would change. I began arranging several VC visits so we could do our ‘dog and pony’ show. Jerry’s role would be to moderate differences that Leon and I had on the direction to go and to learn what had to be learned in order for us to do a clinical trial. Serendipitously, I was able to get the attention of MDS Capital, a Toronto-based VC firm that had an extremely bright and insightful MD/MBA named Jian (Jake) Lu doing their due diligence. He immediately grasped the significance and potential of what we were doing. In short order and with MDS as a lead investor, we had funds to determine if CTCs meant something clinically and so we began clinical testing. The study that Jerry created included the usual radiological methods of following cancer progression in volunteers, while we would measure CTCs. The study went forward, and on and on and on. There were no correlations to be seen between our testing and all of the evaluation methods tested.
Again serendipity came to the rescue. Doyle, whose 2 days a week had stretched into 6 days of effort even though he was still doing his dental practice, had managed to involve Massimo Cristofanilli, an oncologist at MD Anderson, in our work. After our clinical testing had gone on more than 2 years, Massimo called Jerry and said we could take another approach to looking at our data. Massimo realized that we had enough data to look at survival curves and it was time to forget trying to correlate with other methods of following disease progression. In fact, he had done the curves and they conclusively showed that survival rates were well correlated with numbers of CTCs. If a patient had too many, prospects were glum and if CTCs weren’t dropping after chemo, the chemo was not effective.
And with those results, made by efforts of many individuals, each contributing a piece here and there, the key pieces of the puzzle came together and the new world of CTCs was born.