Selfish shellfish cells cause contagious clam cancer

April 10, 2015 8:56 AM

The clam leukaemia is a contagious cancer—an immortal line of selfish shellfish cells that originated in a single individual and somehow gained the ability to survive and multiply in fresh hosts. Until Metzger’s discovery, there were just two exceptions to this rule. The first is a facial tumour that afflicts Tasmanian devils. It spreads through bites, and poses a serious threat to the survival of these animals. The second is a venereal tumour that affects dogs. It arose around 11,000 years ago and has since spread around the world. That was it: two transmissible tumours. Now, there’s a third—and perhaps more on the way.
posted by sciatrix (27 comments total)

Eventually, the whole world will be made up of nothing but strains of cancer, talking about how the hosts sometimes get ideas and think they're running the world, and need to be tamped down.
posted by xingcat at 8:59 AM on April 10, 2015 [10 favorites]

The correct response is, as it has always been, to set fire to the oceans. Fire will purge the unclean.
posted by aramaic at 9:02 AM on April 10, 2015 [6 favorites]

Someone went well out of their way to come up with the phrase "selfish shellfish cells". Try saying it three times fast!
posted by Chocolate Pickle at 9:02 AM on April 10, 2015 [6 favorites]

Eventually, the whole world will be made up of nothing but strains of cancer, talking about how the hosts sometimes get ideas and think they're running the world, and need to be tamped down.

Gaia's all like, "Don't I know it, bra."
posted by leotrotsky at 9:02 AM on April 10, 2015 [3 favorites]

Shelly sells selfish shellfish cells on the sea-shore
The cells she sells are selfish shellfish cells, I'm sure.
For if she sells selfish shellfish cells on the sea-shore
Then I'm sure she sells sea-shore selfish shellfish cells.
posted by leotrotsky at 9:05 AM on April 10, 2015 [12 favorites]

Followed by "causes contagious clam cancer."

Not with a bang, but a whimper. Keep clam.
posted by Oyéah at 9:13 AM on April 10, 2015 [4 favorites]

Not to worry, everything in the ocean will be dead soon enough.
posted by Poldo at 9:21 AM on April 10, 2015 [5 favorites]

That Tasmanian devil cancer remains my most plausible nightmare zombie apocalypse scenario.
posted by deludingmyself at 9:52 AM on April 10, 2015 [1 favorite]

As previously mentioned, it's not the first transmissible cancer, nor will it be the last. Cancer is a highly dynamic complex disease and it constantly blows my mind when reading about new types such as this one. Thanks for the upload.
posted by willowwithe at 10:09 AM on April 10, 2015

deludingmyself - I didn't think of that. Oof.
posted by avoision at 10:09 AM on April 10, 2015

I am so creeped out right now.
posted by djeo at 10:10 AM on April 10, 2015

So um... can it evolve? At what point is it no longer a clam cancer, but a separate species that is parasitical on clams? Is there any evidence for something like that happening before... like a bacterial infection whose DNA is suspiciously similar to its host's, or something?
posted by Leon at 10:16 AM on April 10, 2015

Me too, my hands are clammy.
posted by Samuel Farrow at 10:17 AM on April 10, 2015 [3 favorites]

I remember hearing about the Tasmanian Devil Cancer was thought to be due to the lack of genetic diversity within the population. However, this article linked within the main post indicates there is a far more complex explanation of the transmission, and a possible way to immunize Tasmanian Devils against it to give them a much greater chance of stopping the cancer. Further info here.
posted by chambers at 10:18 AM on April 10, 2015 [1 favorite]

There's a very interesting comment from "Ron" on that page:

This [that the transmissibility of the Tasmanian Devil cancer and another putative cancer that Ron adduces could possibly be put down to the fact that the host population is highly inbred and therefore almost genetically homogenous] can’t be true of the transmissible canine malignancies, though, because this cancer is transmissible to entirely separate canine species including wolves, coyotes, jackals and foxes.

Since hearing about the Tasmanian Devil cancer I've often wondered whether we are absolutely certain the HeLa cell line came from Henrietta Lacks rather than through her.

Since she died in 1951, perhaps we'd have to compare its genome with her children's to be sure.
posted by jamjam at 10:22 AM on April 10, 2015 [4 favorites]

The team discovered that the disease is associated with a jumping gene—a stretch of DNA that can copy and paste itself into a new part of the clam genome. They called it Steamer.

Mmm! Now I'm getting hungry.
posted by TreeRooster at 10:30 AM on April 10, 2015

We also need to consider the possibility that the cancer could produce an even more deadly autoimmune reaction in the afflicted clams, as t-cells siege shells by the seashore.
posted by cortex at 10:43 AM on April 10, 2015 [26 favorites]

Clams can get cancer,
And Cancer's a crab,
And crabs are the cooties
A cooter can have,

And cooters are turtles,
And turtles have shells,
And clams have those too —
Are they cooters as well?

A well is where water
Comes out of the ground.
The ground is for groundhogs,
And groundhogs are brown.

Brown is what bread does
Where toasters are found,
Like in kitchens in houses
In most every town.

A town is a city
With slightly more trees,
And trees produce pollen,
Which cause me to wheeze.

And when I'm not wheezing
I usually sneeze
Because I'm allergic
To that and to bees.

A bee is a letter
Contained in this stanza,
It starts the name Bruce
He's the Boss, unlike Danza.

And Danza's a dancer,
And Dancer's a deer,
And a deer can get ticks
That can live in its ear.

An ear is the corn
That grows out from a stalk,
And stalk is what hunters do
(Quietly walk)

And hunters hunt deer
When they're not hunting ducks
And a duck is a bird
Like a coot is —Aw, shucks!

A coot's not a cooter,
And one shucks an oyster
And oysters aren't clams
And a clam's not a cloister,

And cloisters aren't closets,
But closets are rooms,
Just wee tiny small ones
For storing one's brooms.

A broom has a handle,
And so does a HAM,
A ham is a pig's leg,
A leg is a gam,

And Gam is in Cornwall,
A wall made of corn.
If that was too corny,
Then kill me and mourn,

But don't mourn me too much,
'Cause that could start rumours.
Here endeth my poem
On shellfish with tumours.
posted by Sys Rq at 10:47 AM on April 10, 2015 [31 favorites]

"CLAMS GOT LEGS!" "Those... aren't legs..."
posted by delfin at 11:07 AM on April 10, 2015 [2 favorites]

I thought that HPV was basically a transmissible form of cervical cancer. Or is this something dissimilar?
posted by hippybear at 11:08 AM on April 10, 2015

I thought that HPV was basically a transmissible form of cervical cancer. Or is this something dissimilar?

HPV is a transmissible virus that can induce cancer in the cells it infects (after a certain amount of time - like years - of virally-induced DNA damage). This is a bunch of cancer cells that form a tumor in Organism A, then a cancer cell or two hops over to Organism B, and start growing their own little colony of cancer cells that forms a new tumor. Although the clams one isn't forming tumors, because it's a bloodbourne cancer. Whee!
posted by deludingmyself at 11:33 AM on April 10, 2015 [4 favorites]

jamjam: You might be interested in reading The Immortal Life of Henrietta Lacks. HeLa cells are certainly human, which is why they have been so invaluable to research in making vaccines and studying drugs. There have also been some very unethical experiments done; there was a doctor in 1954 (Chester Southam) who injected live HeLa cells directly into the arms unwitting patients. Few people with strong immune systems ended up with tumors from it.
posted by foxfirefey at 11:37 AM on April 10, 2015 [2 favorites]

I wonder if the living clam cancer isn't a cell line dumped down the drain from a lab somewhere? Anyway.

Labs don't get a lot of,"What if?" or, "What about?" money." I wonder if tumor DNA data bases check the DNA of tumors, against the DNA of the post surgical patients?

There once was a grand liver surgeon,
Whose business, it was a'surgin'.
Just get me that scope,
Believe me you dope,
I don't care if it's dirty or virgin!
posted by Oyéah at 12:44 PM on April 10, 2015

That's a fun what-if, but since I skimmed the paper, I'm gonna pour cold water on it! :)

The answer's a clear no. The clam cancer cells have really high activity of new retroelement called Steamer - it's a stretch of DNA that re-integrates many many copies of itself into the clams' blood cells, and all that copying and random insertion of this stretch of DNA wreaks enough havoc to lead to genomic instability, one of the major hallmarks of cancer. All of the clams seem to have Steamer, but this line of transmissible clam cancer has a ton of Steamer activity.

You're right that "what if?" money is rare, but once you have a single stretch of DNA (like the open reading frame for Steamer) that you're interested in examining further, it's fairly easy (and routine) to analyze what kind of sequence that is, and compare it to the entire known corpus of other research-generated DNA sequences to see if it resembles anything else out there. In this case, the researchers note that Steamer (like other retrotransposons) kind of resembles some of the same proteins you'd find in a retrovirus (like HIV), but its closest genetic similarity is to another retrotransposon sequenced from the sea urchin.

You could go ahead and blame some generations-back clam that ran into a sea urchin, maybe.
posted by deludingmyself at 1:12 PM on April 10, 2015 [1 favorite]

Leon, the transmissible canine cancer has been described in the past as a "highly degenerate mammal".
posted by cromagnon at 3:57 PM on April 10, 2015

Thanks Sys, now I'm reading metafilter comments in rhyming couplets.

Love your poem BTW.
posted by Samuel Farrow at 5:06 PM on April 10, 2015

"Highly degenerate mammal"? Wow. If so, it would certainly be its own species, but it's different enough that even "species" doesn't really cut it. I don't think we have a good word for a taxonomic rank that represents a sideways step into a different type of being.
posted by Joe in Australia at 6:18 PM on April 11, 2015