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Can a Tumor Have a Baby? – Embryology

by John McLachlan, PhD
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    00:01 Now I have posed a very startling question here which is can a tumor, can a cancer cell have a baby? So let me explain what I am asking here. What we already know is that at very early stages of development, then cells are very flexible. You can remove cells from a developing embryo at the morula stage and the cells that have been removed will just be replaced and development will continue as normal. So you could remove half of the cells at the four-cell stage and you will still get a normal individual developing. Perhaps even more unexpectedly you could push two morulas together and they will form a double sized aggregate and if you implanted that in a mother, it will give rise to an individual, which is also normal in size.

    00:49 In other words, it will regulate for the extra number of cells. Most of these experiments are carried out in mice, as I said, it would be illegal to carry them out in humans.

    01:02 So you can create a multiple embryo from different sources. So what you can do is to take morulas from two different strains of mice, say a brown mouse and a white mouse and you can push them together and allow them to develop inside the mother being prepared for pregnancy and what happens is that it will give rise to a mouse that is normal in size that will be a patch work. Some of the cells come from one cell appearance and other cells come from another cell appearance. So effectively, it is a patch work mouse with 4 parents altogether.

    01:39 What you can do something even dramatic, which is - you can take a morula from one mouse embryo and you can take some tumour cells from another mouse embryo and usually the tumour cells are used here are developmental tumours called teratocarcinomas. And if you push the mouse cells together with the tumour cells, the teratocarcinoma cells, you get a patch work combination. If you insert that combination into a mouse mother that has been prepared for pregnancy. In time, she will give birth to a patch work mouse. Some of the cells come from the parent mouse and some of the cells from the tumour. But the interesting thing is that the tumour cells are now behaving properly. They are not tumour cells anymore.

    02:27 Somehow they have been restored to normal behaviour by being combined with signals from a normal mouse. Now let us imagine half of the cells come from the tumour and they are scattered through the entire body of the mouse. So some of them will be populating the ovaries or the testes in female and male mice respectively. So if you meet two mice like that of different sexes and then bred them, some of their offspring will have tumours from mothers and fathers and again these mice are normal and they are not more liable to get cancer than any other mouse. So the developmental signals have in this case restored that developmental tumour to behaving normally and that is a very striking observation.

    03:15 Now I would like to look up a relationship between embryos and cancer. So let us look at some of the cell properties that underlie the embryonic development and the first is that the cells can move about. So there is lot more flexibility, cell migration taking place in the developing embryo, than there is in the adult. So movements are regular part of development. Also, embryo cells are dividing very rapidly. Embryos grow faster than the fastest tumours can grow. So there are high rates of cell division especially when compared to the adult. And then cells begin as being relatively undifferentiated and gradually they move towards the differentiated stage during the course of development.

    04:02 And then they interact with each other. So for instance muscle cells will attract blood vessels towards themselves that does not have to be specified by the genome in detail.

    04:13 You know that anywhere where a muscle begins to develop, blood vessels will grow towards it and those tissue interactions are a valuable clue as well. By the time you get to be an adult, many of your cells are differentiated, cell division has either ceased or is highly controlled, and cell movement is relatively rare. Now let us compare that with cancer cells.

    04:38 One of the big problems about cancer cells is that they can invade and spread, in other words, metastasized throughout the whole of the body. Another issue is that they divide very rapidly, much more rapidly than normal cells in the body. They also tend to de-differentiate.

    04:57 So the more de-differentiated they are, the more dangerous the cancer is. So if the cancer is biopsied, the cells are still well differentiated, the chances are that's a more benign cancer than one with the cells of de-differentiated with no longer showing signs of the parent tissue that they came from. We know that cancer cells can also attract blood vessels just as muscles can in early embryonic development and this is a serious problem. Once the tumor attracts blood vessels towards itself, they can then begin to grow rapidly and cells can detach from the tumour and spread through the rest of the body in the blood system as a result. So what we can see is that in cancer, cell division and cell movement have escaped from the normal control. So if you compare that with the things happening in the embryo, you can see the cancers have in many ways reverted to the behaviour which is normal for embryos. The reason cells have the ability to move about to invade other tissues is because embryonic cells have those abilities and they move about in the body. So what this implies is that if it could understand the developmental mechanism that lie behind embryonal cell behaviour, then that might well give this really valuable clues to understanding and dealing with cancer cells and their properties.


    About the Lecture

    The lecture Can a Tumor Have a Baby? – Embryology by John McLachlan, PhD is from the course Embryology: Early Stages with John McLachlan.


    Author of lecture Can a Tumor Have a Baby? – Embryology

     John McLachlan, PhD

    John McLachlan, PhD


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    Understanding basic early cell behavior.
    By Tomas B. on 24. July 2018 for Can a Tumor Have a Baby? – Embryology

    Is simple and makes clear, easy to understand remarks about cell dynamics at different stages of the early phases of cell division and differentiation.