[Nescafe]

Hi,

How does one go about "making" different types of cancer cells for testing? I am guessing each cancer cell has some unique molecular targets but I am uncertain.

Thanks,

Nescafe.

[fledarmus]

The answer to this question is very specific to the cell line that you are producing.

Just using your example, think about the differences in lung cells and brain cells. Lung cells are specialized epithelial cells, while brain cells are specialized nerve cells. So if you make a cancer cell from a lung cell, the resulting cancer cell would be different from one that was made from a brain cell.

Then you have to get into the mechanisms that a) make a cell cancerous, and b) make a cell line "immortal" so it can be grown in cultures. Many of the first cancer cell lines were extracted from tumors that had been removed from the body. The extracted cells were separated and plated out, and the ones that grew and maintained cancer characteristics were developed into stable cell lines for testing. These cell lines were studied to find the differences between them and normal cells that led to the cells becomind cancerous. Depending on the type of cancer, the source cell line, and the stage of the cancer, there could be only one or two mutations from the original cell type, or there could be enormous numbers of mutations. Especially since one of the processes that can lead to cancers is a defect in the cells machinery for detecting and preventing mutations.

If you have specific types of cancer in mind, do a PubMed search. That will lead you to representative cell lines that are used to model the cancer in the lab, and to the specific genetic and morphological differences between them and the normal cells from which they were derived or which they are intended to model.

[curiouscat]

The answer to this question is very specific to the cell line that you are producing.

Just using your example, think about the differences in lung cells and brain cells. Lung cells are specialized epithelial cells, while brain cells are specialized nerve cells. So if you make a cancer cell from a lung cell, the resulting cancer cell would be different from one that was made from a brain cell.

Silly question: What happens during metastasis? How do specialized cells spread to other sites?

[Yggdrasil]

Silly question: What happens during metastasis? How do specialized cells spread to other sites?

This is definitely not a silly question and is a very active area of research.  We currently do not know a lot, but I'll post a little bit from a good review on cancer:

The multistep process of invasion and metastasis has been schematized as a sequence of discrete steps, often termed the invasion-metastasis cascade ( [Talmadge and Fidler, 2010] and [Fidler, 2003]). This depiction envisions a succession of cell-biologic changes, beginning with local invasion, then intravasation by cancer cells into nearby blood and lymphatic vessels, transit of cancer cells through the lymphatic and hematogenous systems, followed by escape of cancer cells from the lumina of such vessels into the parenchyma of distant tissues (extravasation), the formation of small nodules of cancer cells (micrometastases), and finally the growth of micrometastatic lesions into macroscopic tumors, this last step being termed “colonization.”

Hanahan and Weinberg 2011 Hallmarks of Cancer: The Next Generation Cell 144: 646. doi:10.1016/j.cell.2011.02.013.

I think of metastasis as an evolutionary process.  As a primary tumor grows, it begins running out of space and resources.  Thus, any cells that acquire mutations that allow it to separate itself from the tumor and move into a different region of the body where more resources for growth are available will have a selective advantage.  Of course, this process is difficult and cancer cells face a number of challenges in becoming metastatic.  First, the cells must evolve a means to escape the tumor.  Current research suggests that many cells overcome this challenge by activating a cellular program called the epithelial-to-mesenchymal transition, a process normally involved in embryonic development and wound healing.  This program reduces the expression of the cell adhesion proteins that keep the cell anchoring to its neighboring cells and shuts of the apoptosis (programmed cell suicide) that would normally occur for a cell that has been removed from its niche.

These cells must then somehow find a new niche in the body which they can colonize and establish a new tumor.  This process is obviously very difficult and many of the cancer cells that escape the primary tumor likely fail to survive outside the primary tumor.  Those that do, however, can then go on to establish new tumors throughout the body.

If you are interested in the topic, I would urge you to read the Hanahan and Weinberg review as it provides a very good overview on cancer in general, and has a pretty informative section on the mechanisms of metastasis.

[curiouscat]

Thanks @Yggdrasil! Very interesting stuff indeed. Thanks for the tip about the review. Will be interesting to read.

[Nescafe]

The answer to this question is very specific to the cell line that you are producing.

Just using your example, think about the differences in lung cells and brain cells. Lung cells are specialized epithelial cells, while brain cells are specialized nerve cells. So if you make a cancer cell from a lung cell, the resulting cancer cell would be different from one that was made from a brain cell.

Silly question: What happens during metastasis? How do specialized cells spread to other sites?

There is no such thing as a silly question. I was just curious, curiouscat, you should know better (your username and all). Might as well ask and learn from people on this forum who are very knowledgeable such as Yggdrasil, Fledramus and Babcock_hall.

[atlasman84]

added question : Is that this two type of cancer have same DNA

[fledarmus]

In a single normal individual human, all cells come from a single embryonic cell, and theoretically have the same DNA. However, there are 3 billion base pairs in the DNA of a single human, and even though the chance of mutation for any cell division is very, very small, there is a non-zero chance of mutation any time the DNA is replicated. So it is possible comparing any two cells in a single individual that you may find differences in the DNA on the order of parts per billion.

Specialization of cells for various systems can change the DNA content for that cell. For example, germ cell lines (sperm and egg cells) only contain half of the nuclear DNA of a normal cell. Red blood cells have no nucleus, and have none of the nuclear DNA of a normal cell. Mitochondrial DNA is a completely different issue. And in certain specialized cells, mechanisms are in place which prevent certain parts of the DNA from being accessible to transcription, locking out parts of the genetic code from access by the cell machinery. This is one difference between stem cells and non-stem cells - both contain the same DNA, but in non-stem cells, parts of the DNA are locked out.

If the mutations that make a cell cancerous were present in the embryo, the embryo would be non-viable. Therefore, for cancer to occur, there must be mutations in the cell after the individual is born. That isn't to say that there aren't mutations in embryos which lead to cancer, but they are almost always mutations in the error-correcting mechanisms of the cell and their true effect is to make it much more likely that subsequent cell divisions will produce mutations. It is the accumulation of mutations and mutations in critical genes which cause a cell to become cancerous. Most mutations in critical genes simply make it impossible for a cell to survive and it never reproduces, but very, very occasionally, a mutation in a critical gene will cause the cell to break the normal controls in the system on cell replication. At this point, the cell production increases, and tumors form.

With all of that as background, let me try to answer your question. Will two types of cancer have the same DNA? If they come from two different individuals, unless both individuals formed from the same original embryo (identical twins), absolutely not. Even normal cells from two different individuals will not have the same DNA. The differences may be very tiny, but they are there.

What about two types of cancer in the same individual? There are two different ways this might happen. One is that there is an inherent genetic defect in the error-correcting mechanisms of dividing cells in an individual. In this case, spontaneous tumors can arise in several places throughout the body. All of those tumors will be different, however, because the errors in cell division are for the most part random - it will simply result in a shotgun approach to knock out critical genes that prevent unregulated cell division.

The other way an individual might have two different cancers is that one cancer formed first and then metastisized. This requires mutations in several parts of the genetic code, knocking out both the regulation of cell division and the adhesions that cells form to each other. This typically happens because one of the earlier mutations in the cancer was a mutation that knocked out one of the error-correcting mechanisms. Again, the chances are that mutations are accumulating far more rapidly during cancer cell divisions than in normal cell divisions, and the metastasized tumor, having probably started from a uniquely mutated tumor cell, will have a (very very slightly) different DNA than the original tumor.

The short answer - no, even within a single tumor there are almost always genetic differences between tumor cells, simply because in most cases the error-regulating processes are broken and errors are accumulating with each cell division. However, these differences are on the order of a few changes in 3 billion base pairs, which is an incredibly small difference even compared to normal differences between non-identical twins. The DNA of an individuals lung cancer, for example, would be far, far more similar to the DNA of that person's normal cells than it would be to the lung cancer of another individual any less closely related than an identical twin.