Viewing a single comment thread. View all comments

Allchemyst t1_iw33tqx wrote

Reply to comment by Chiperoni in How do medical researchers obtain lab animals with diseases like specific forms of cancer which arise spontaneously? Do they raise thousands of apes and hope some eventually develop the disease? by userbrn1

To continue on this:

It's not just done genetically. Xenografts are done pretty consistently in cancer studies. You take a small piece of tumor that and implant it; usually, into a mouse that has been inbred to specifically knockout their immune system (or important parts of it anyway). This also gives you the advantage of being able to test against a human tumor in an animal model.

They also inject tumor based cell lines in order to produce a false tumor.

482

Chiperoni t1_iw3452f wrote

Very true. And ideally a “mother” stock of the original tumor or cell line can be stored and expanded when needed if you want to reproduce the same tumor.

118

scrangos t1_iw3z136 wrote

I've been meaning to ask something about this, isn't cancer prone to further mutations? When you try to expand it, wouldn't it end up changing sometimes?

42

Suricata_906 t1_iw4gg08 wrote

Yes, that is true, but it takes some rounds of replication . That’s why for studies you would want to freeze a big batch of tumor tissue or cells, take out a vial for to use once and go back for another vial later. Essentially you are minimizing genetic drift for experimental purposes. Not perfect, but then what is?

65

scrangos t1_iw4i78s wrote

Yeah that makes sense. Are those immortal cancer cells that have been used for a long time also been drifting genetically? Has there been a track record of how they've changed over time?

13

GoblinGeorge t1_iw4t5vs wrote

HeLa cells have been drifting. There are studies that show cells from different labs have genetic differences, but I don't think it's possible to track all the variations in all the different lines. There are just too many different lines at this point.

23

Suricata_906 t1_iw53p66 wrote

No track record as far as I know, but everyone assumes they are not as originally isolated. HeLa cells still have the original HPV induced mutations but unspecified other ones. When was a lab worker, the protocol was to use cells like that for maybe 15-20 population doublings, then discontinue.

The ATCC (American Type Culture Collection) is the motherlode for all kinds of cells, from the fairly normal, to things like HeLa that I like to say would grow on walls!

Fun fact. Most cells cultures isolated from normal human tissues have an expiration date called the Hayflick Limit of 50 or so population doublings before they become senescent and won’t divide. immortalizing mutations of various kinds override that.

10

corduroy t1_iw6n9ae wrote

Just to add, there's a lot less genetic drift when passaging in vivo as compared to in vitro.

3

ObscureCulturalMeme t1_iw4pkaz wrote

The lesson I'm hearing is that cancer can be raised just like a sourdough starter. Got it.

^(yes there's an /s)

35

Veni_Vidi_Legi t1_iw53zdi wrote

There are transmissible cancers too, like with dogs and Tazmanian devils.

15

AkioDAccolade t1_iw5bl5o wrote

Isn't it possible that most cancers are transmissible given the right scenario?

I vaguely remember reading an article about a medical professional who died of skin cancer despite never having skin cancer, but she did experience an accident where she accidentally sliced herself with a scalpel that was being used to excise a cancerous growth in an elderly patient?

9

15MinuteUpload t1_iw5nowu wrote

In immunocompetent individuals it's unbelievably rare for a traditionally non-infectious cancer (i.e. all of them except the dog and Tasmanian devil ones) to be able to establish itself in another host, even if the cancer is directly implanted into the host. Part of the reason a natural/endogenous cancer can be so hard for the body to take care of is because it's composed of the host's own cells, which are obviously recognized as "self" and therefore less likely to come under attack by the immune system. Foreign cancers of course do not have this innate defense and so will almost always be very quickly killed off by the host's immune system.

10

wulfoftheorderofbio t1_iw66eoy wrote

I was gonna say, seem to recall learning through immunology that the immune system does a pretty decent job fighting off most cancers that try to grow since the body considers them "foreign?" I need to brush up on immunology. It has been 8 years and my memory isn't what it used to be.

2

Veni_Vidi_Legi t1_iw5qbzo wrote

> Isn't it possible that most cancers are transmissible given the right scenario?

Such a cancer would have to be able to survive exposure during the transmission process while also being in the right place and condition to transfer to a susceptible host site.

Once there, the immune system would almost certainly kill the more foreign looking cancer, as it almost always does for the more similar looking native cancers that arise in the host. But if it can evade the immune system, or if the immune system were missing, then it would have to find a suitable site and then maybe it can take hold.

So there would be a lot stacked against most cancers.

4

Chemputer t1_iwoiwzh wrote

Not particularly, not in humans, no. It's even one of the misconceptions/myths on cancer.gov not specifically that story you mentioned (I googled my best and couldn't find it), but that cancers are contagious.

If what you remember reading is actually what you read and it's actually true (not a knock on you, just far more likely for your memory to be your brain trying to confabulate a story from something different, possibly vaguely related. Our memory sucks, especially fuzzy ones, and our brain just fills in the gaps), perhaps it was a cancer caused by a virus or bacteria (which is very possible, some decent percentage -- I've read 15-20% but can't find a citation for that exact number -- of cancers are linked to viruses or bacteria) and said pathogen spread, then causing cancer. The cancer itself would not spread in that manner.

1

AkioDAccolade t1_iwok10y wrote

So I looked it up when I remembered it but I'm having difficulty finding the case study for a third time, but in the case I was remembering it was indeed a nurse that contracted it, however she was HIV+ (that she acquired during another accident, guess she would have taken the hint) which is the part I was missing. It was sometime in the early 90s

That pretty well makes anything possible.

1

LilyMeadow91 t1_iw6ktep wrote

This is actually a quite good comparison, even if it was meant sarcastically 😅

Sourdough starters are just bacterial cell cultures, and concepts for cancer cell culture are the same: you give them jar to live in, the right temperature and appropriate food 😅

4

ScienceIsSexy420 t1_iw37e4z wrote

Additionally, these induced tumor cells have the advantage of being isotopically labeled, making tracking the tumor progression much easier to quantify for comparisons.

38

Astaro t1_iw46u0v wrote

Why would new cancer cells include the isotope labels of thier parents? Wouldn't the amount of isotope halve with each cell division?

10

Chemputer t1_iwok3yc wrote

Of course, but it's very long down the line before it becomes undetectable much less low enough to be baseline.

That is actually useful in determining how many cell divisions have happened.

1

Wankeritis t1_iw4z9z3 wrote

This also works with human leukaemia samples. You inject leukaemic bone marrow into mice and they home to the mouse's bone marrow and proliferate so you can harvest more of the sample than you injected.

2