Special topic: circulating tumor cells

How are you? Today we would like to share some information about circulating tumor cells. I would like to touch the basis of basic science and then moving right along to the clinical application and then maybe touch a little bit about future development. And I am Yun-Yen and I represent the Taipei Medical University. I would like to use this opening slide to share the what we are dealing nowadays. And to talk about bio-marker it has been running for about 10 to 15 years.

We try all the ways to find out what is the best marker in guiding our cancer therapy We can use the molecular target and in target it on the marker which we identify from the molecular biology from pathology and that could be a DNA mutation such as EGFR or maybe a fusion gene such as ALK ERM4 etc. But more importantly all these biomarker what we are trying to use is try to improve our clinical therapy and survival rate. In circulating tumor cells in recent years has become one of the very unique biomarker that has covered almost all of

what I have mentioned such as : DNA mutation fusion protein and the cell numbers as well. In this slide just to share with you what is circulating tumor cells are all about. The tumor itself can shedding lots of the cells out and then these cells will invaded through the basement membrane and gradually circulating in the vascular systems. Once they touch the soil they get the new neovascularization they start to grow another colony. So circulating tumor cells itself is critical in playing the initiation role in the metastasis cascade. So the background about the circulating tumor cells is really covered many other

things such as : what is the single cells can circulate in so many blood cells around that how can they against the forced from the bloodstream. All of that still remain lots of the research From the physiological and biological both sides. And the morphology of the circulating tumor cells can also varied they are not just around the cells in the circulating systems. They could be fragmented as well but we don’t know whether these fragmented cells still have the same meaning in biology point of view. So that is also a very important biological research as well. But more critical is since they can invaded out so they really carry on lots of genetic machinery changes especially epithelial mesenchymal transformation.

Which we generally use the term called EMT and of that also related with it stemness which is another unknown biology point of view require further efforts to put on. But how to detect the circulating tumor cells? At the beginning we use the cell search system. Which the FDA approval equipments. Also there is a brand name to call cell search called the radex. That is used monoclonal beads to bind antigen of the cells and then take it out by the sorting systems. However this is not the only systems now There is many other systems on-board as well. But clinically that become important just the recent years.

Using the circulating tumor cells as one of the example in biomarkers actually started about early 2000. At that time we really don’t know how to use that. The only thing we know is in numerations. We count how many cells we can collect it in the circulating tumor cells. But numeration is not enough for us and not enough to improve our scientific biological evidence at all. So in about the year 2014 there is a critical moment for circulating tumor cells because the metastasis staging we are using called the staging systems. One of that is called AJCC staging system adapt CTC circulating tumor cells to become one of the staging marker also using that for the prognostic predictive marker.

That become very critical. That is the first time CTC no longer just numeration. Also involve into staging and trajectory for the prognostic evidence in cancer and cancer treatment. In this slide just to share with you from the literature that is a very early evidence to suggest from the breast cancer prostate cancer as well as colon cancer. CTC numeration plays some role. And if you have a 7.5 ml blood cells collected from patient. If you can identify 5 or above 5 cells collected from breast cancer or prostate cancer that is meaningful in survival benefit. And same thing in colorectal cancer. 3 or above 3 cells collected from the 7.5 ml also as a certain survival meaning.

And gradually gradually more evidence adding on from different circulating tumor cells collecting systems. Also in different disease. Even in brain tumor as well. In this slide just to quickly share with you nowadays circulating tumor cell collection involving many many different methodology. Not just the magnetic beads but also the use of micro-fluidity they also use lots of gravity mechanical methods to collect to sorting. That is a very important medical device research field and going to impact a lot in cancer therapy. One of several publications came out in recent years in talking about the comparison in all these different methodologies and this is the micro-fluidity collecting circulating tumor cells. They also compare the cell search vs. micro fluidity.

And this is just the one literature and one example. There are many other examples to talk about comparison or competitive among all these systems. But more important is we all need to use the methodology in understanding better about our disease and moving that to the therapy. So our endpoint is not just numeration count the cells anymore. Important is we collect the cells and study that single cell for our research. And from the research we move to the clinical decision such as how to decide to using different drugs. So the single cell becomes mainstream from the CTC collections.

We are collect the cells and then we understand genetics about these cells and using these generic c markers to predict what going in our patient and also help us to decide about whether we should switch the treatments. And more important is these genetic study leading us to the very different field such as stem cells but important is the methodology need to be very steady in your hand otherwise variation can be quite a range. And also from learning the systems we identify not just the tumor cells we can also see some stromal cells. We can see both why and how these stromal cells the meaning in our system. Are they play some role in drug resistance or not.

That is the current mainstream of the research. Single cell research become critical in circulating tumor cells CTC. Not just for one disease also for metastasis disease. More important is the different diseases side. They have heterogeneity of the genetic background and which genetic background can lead the metastasis can become very critical clinical questions. So single cell study will guide us lead us to better understand why some mutation can play some role or override the other clones and we are fully understand the importance but we need lots of equipment and technology and more important is the expertise in dealing with the single cell because the single cell analysis is very challenging and this is just one example.

Published in science in year 2014 you can see you can collect the circulating tumor cells. You can make it out of single cells and then you can also make the ex-vivo expansion. After that you can implant into the mouth models. You take it out mouse model you are looking for the Molecular evidence. You can compare the pre and post treatments or pre and post implementations. All these molecular target markers can all be identified and the most critical is we can use the system to select the drug in helping our patients.

Needless to say in the same technology we can analysis each single clone and look at the genome changes and we need to better understand why these changes coming from and why some changes play superior role and that will help us to better understanding the tumor biology and oncology therapeutic research. This is the last slide I would like to share with you. It sounds very easy to talk about circulating tumor cell and how to collect it but some evidence you need to take home that still a needle in the haystack and it is not easy technology. You heavily rely on professional expertise and good equipment because the tumor really shed a lot of circulating tumor cells.

From 1 gram of tumor tissue it can shed out about 1 million cells but within 24 hours only 0.1% are still alive. And less than 0.01% survive and then has the potential to produce metastasis clone. So with all of that you also need to think about how to pick this single cell from millions and millions of monoclonal cells mononuclear cells from the peripheral blood. That is work can be done. So CTC is the window for our future cancer research and translational critical point. Thank you!