Flame_
Well-Known Member
It seems to be the case that greys have more of a predisposition to cancer and tumours than all the other colours. Does anyone know the reason for this? Something I've been wondering about for ages.
Greys and Cancer/Tumours
- Thread starter Flame_
- Start date
merlinsquest
Well-Known Member
Lack of pigment in the skin, therefore less protection against the damaging rays of the sun ...same reason why fair people are more likely to get skin cancer than black people!!
kerilli
Well-Known Member
i think Merlin's right.
i don't think i've ever seen anything other than a grey with melanomas, for instance.
i don't think i've ever seen anything other than a grey with melanomas, for instance.
alleycat
Well-Known Member
Its something to do with the movement of pigment in the coat.
Greys retain their dark skin under the (ultimately) white coat- so they are actually LESS likely to be affected by the sort of problems that merlin mentions; the white coat reflects heat & the dark skin protects against the suns rays, so they have the best of both worlds, unlike bays, say (dark coat) or coloured horses (pink skin). I remember an Arab breeder telling me that greys are favoured in hot countries because of
this. In fact if you put your hand on a light grey horse on a hot day, it will feel cooler than a bay.
However, they DO get melanomas, and though I don't understand how this works, its connected with the movement of pigment associated with the grey going lighter.
The melanomas that result are usually benign; they might get in the way but they don't spread; but for some reason especially in older horses, one will sometimes become malignant and spread through the body.
My grey mare had one about the size of a pea under her dock for most of her life; when she was 27 / 28 this turned into two, then three, which also increased slightly in size. She was PTS for other reasons at 29- age had caught up with her & she suddenly had a string of small ailments.
Greys retain their dark skin under the (ultimately) white coat- so they are actually LESS likely to be affected by the sort of problems that merlin mentions; the white coat reflects heat & the dark skin protects against the suns rays, so they have the best of both worlds, unlike bays, say (dark coat) or coloured horses (pink skin). I remember an Arab breeder telling me that greys are favoured in hot countries because of
this. In fact if you put your hand on a light grey horse on a hot day, it will feel cooler than a bay.
However, they DO get melanomas, and though I don't understand how this works, its connected with the movement of pigment associated with the grey going lighter.
The melanomas that result are usually benign; they might get in the way but they don't spread; but for some reason especially in older horses, one will sometimes become malignant and spread through the body.
My grey mare had one about the size of a pea under her dock for most of her life; when she was 27 / 28 this turned into two, then three, which also increased slightly in size. She was PTS for other reasons at 29- age had caught up with her & she suddenly had a string of small ailments.
D
Donkeymad
Guest
The sun aspect doesn't actually make much sense. Greys are most likely to get melanomas under the dock, which is obviously a part where the sun don't shine (unless your horse is an angel)
Bossanova
Well-Known Member
Alleycat's right, it's movement of pigment and essentially a tumour which stems from a build up of pigment. They dont just get melanomas on the skin, the deadly ones are generally intestinal
SirenaXVI
Well-Known Member
[ QUOTE ]
Lack of pigment in the skin, therefore less protection against the damaging rays of the sun ...same reason why fair people are more likely to get skin cancer than black people!!
[/ QUOTE ]
Greys actually have dark skin rather than pink skin and the melanomas they get are nothing to do with sun damage. It's actually to do with the dispersion of the pigment and melanomas are not to be confused with carcinomas which can be caused by sun damage. Greys are actually no more predisposed to cancer than any other colour, and, although the latest estimation is that 99% of greys will have at least one melanoma, they are benign and rarely cause problems unless they grow so large that they interfere with other organs.
Lack of pigment in the skin, therefore less protection against the damaging rays of the sun ...same reason why fair people are more likely to get skin cancer than black people!!
[/ QUOTE ]
Greys actually have dark skin rather than pink skin and the melanomas they get are nothing to do with sun damage. It's actually to do with the dispersion of the pigment and melanomas are not to be confused with carcinomas which can be caused by sun damage. Greys are actually no more predisposed to cancer than any other colour, and, although the latest estimation is that 99% of greys will have at least one melanoma, they are benign and rarely cause problems unless they grow so large that they interfere with other organs.
Bananarama
Well-Known Member
My friends pony is a grey, she had many pea sized melanomas under her dock (around 6 or 7) and one on her neck which is about the size of a chunky hoof pick but about half the length.
And here is what a vet says on the matter....
[ QUOTE ]
Melanomas are relatively common tumours made up of cells in the skin, which produce the pigment called melanin. They are particularly common in grey horses and often cause no problem. There is however always the danger that such lumps will become cancerous.
The reason this happens is not always clear, but it is normally related to a weakening of the horse's immune system. Tumour cells of all kinds are abnormal cells and the body naturally tries to destroy them, but it is often not strong enough to do so quickly.
Keeping any horse as healthy as possible will help to maintain a strong immune system. Feeding is the most important factor, but I am afraid that feeding horses for a strong immune system as nature intended is not easy. A natural diet comes from a large grazing area with access to a large variety of different plants growing on different soil types.
In an artificial environment, we supplement the horses grazing with concentrates and supplements know to boost the immune system in order to make up for any deficiencies that might exist in his diet.
For long term supplementation, I would recommend as good a vitamin and mineral supplement as you can afford plus a little seaweed for a few months each year and the use of selected herbal formulae.
I would be wary of Echinacea-based products because these are not suitable for long term support of the immune system and are better used when specific infections are known to be near at hand or have just started to cause problems.
[/ QUOTE ]
And here is what a vet says on the matter....
[ QUOTE ]
Melanomas are relatively common tumours made up of cells in the skin, which produce the pigment called melanin. They are particularly common in grey horses and often cause no problem. There is however always the danger that such lumps will become cancerous.
The reason this happens is not always clear, but it is normally related to a weakening of the horse's immune system. Tumour cells of all kinds are abnormal cells and the body naturally tries to destroy them, but it is often not strong enough to do so quickly.
Keeping any horse as healthy as possible will help to maintain a strong immune system. Feeding is the most important factor, but I am afraid that feeding horses for a strong immune system as nature intended is not easy. A natural diet comes from a large grazing area with access to a large variety of different plants growing on different soil types.
In an artificial environment, we supplement the horses grazing with concentrates and supplements know to boost the immune system in order to make up for any deficiencies that might exist in his diet.
For long term supplementation, I would recommend as good a vitamin and mineral supplement as you can afford plus a little seaweed for a few months each year and the use of selected herbal formulae.
I would be wary of Echinacea-based products because these are not suitable for long term support of the immune system and are better used when specific infections are known to be near at hand or have just started to cause problems.
[/ QUOTE ]
alleycat
Well-Known Member
Amazing- so my old mare's melanoma started to take over as her system started to fail?
Flame_
Well-Known Member
Wow thanks everybody. That makes sense, melanomas relating to the change in coat colour and also the immune system. I love this forum, you can learn all sorts!
bexandspooky
Well-Known Member
Spooks has some under his tail, one a little bit behind his ear and just recently one appeared behind his front leg. Being 18 now it makes me wonder how many are popping up inside all ready to cause blockages etc.
SirenaXVI
Well-Known Member
[ QUOTE ]
Spooks has some under his tail, one a little bit behind his ear and just recently one appeared behind his front leg. Being 18 now it makes me wonder how many are popping up inside all ready to cause blockages etc.
[/ QUOTE ]
My old girl had one the size of a pea under her dock since she was about 6, she has recently developed more under her tail and also on her udders. As she is nearing 30 I have decided to leave them alone as, apart from that she is disgustingly healthy.
Spooks has some under his tail, one a little bit behind his ear and just recently one appeared behind his front leg. Being 18 now it makes me wonder how many are popping up inside all ready to cause blockages etc.
[/ QUOTE ]
My old girl had one the size of a pea under her dock since she was about 6, she has recently developed more under her tail and also on her udders. As she is nearing 30 I have decided to leave them alone as, apart from that she is disgustingly healthy.
Fransurrey
Well-Known Member
I wrote an article on this a while ago and posted a summary of it on another forum. I will try to find it for you, but there's rather more to it than what is above!
Bear with me (and prepare for a Biochemistry lesson...).....
Bear with me (and prepare for a Biochemistry lesson...).....
foxviewstud
Well-Known Member
like others have said due to the pigment in the skin, also white dogs and cats are very prone to cancer and other health issues
Fransurrey
Well-Known Member
OK, I found the article and copied and pasted the relevant bits!
Re: the vet's comments above. Whilst it's true that the immune system can influence susceptibility to tumour development, this does not explain why greys would be more likely to develop them.
Anyhoo, here's the summary of my piece!
---------------------------------------------------
"Mitf implication in the increased rate of tumour development in grey horses"
Mitf is a protein whose phosphorylation (addition of a phosphate group) is dependent upon stress. The more stress, the more phosphorylation. For example, rats which see/smell blood from other rats being killed in the lab are later found to have a much higher quantity of phosphorylated Mitf (discovered accidentally!).
So, stress signalling activates Mitf by phosphorylation (amongst other things), which gives rise to the activation of melanocyte stem cells (cells which still have the potential to differentiate into other types of tissue), but out of synchrony with the hair cycle. Hair of course is constantly lost and replaced, with the melanocyte being responsible for the pigmentation of hair. So, if melanocyte activation is out of sync with the hair loss/replacement (hair cycle), you get premature greying. Another side effect is the activation of quiescent (dormant/inactive) melanoma stem cells, giving rise to their proliferation. Over-stimulation of the proliferative (cell growth/division) pathways increases the likelihood of cancer in this case malignant melanoma.
Stress signalling can involve UV (too much sunbathing!) or other physical stress, including emotional stress, although the latter is still being investigated.
It seems that greys are much more likely to develop malignant melanomas. The reason is this. They have a mutation in the Mitf gene (MitfVIT), which increases the activation of Mitf, in the same way that stress does, so you have effectively twice the amount of stimulation and Mitf is continuously activated, as though the horses skin cells were under constant stress. In other words, in MitfVIT cells, the phosphorylation occurs regardless of whether or not stress is applied to the cell.
These are the horses which turn grey very early on in life. So, this dramatically increases the chances of a melanoma developing, when added to additional, environmental stimuli. I believe that this applies to greys that are born black I dont think it applies to chestnut born greys, as this is due to a different mutation, not directly connected to Mitf. I'm not clear on this bit, although I do know that chestnuts produce eumelanin, a variant of the normal melanin.
Re: the vet's comments above. Whilst it's true that the immune system can influence susceptibility to tumour development, this does not explain why greys would be more likely to develop them.
Anyhoo, here's the summary of my piece!
---------------------------------------------------
"Mitf implication in the increased rate of tumour development in grey horses"
Mitf is a protein whose phosphorylation (addition of a phosphate group) is dependent upon stress. The more stress, the more phosphorylation. For example, rats which see/smell blood from other rats being killed in the lab are later found to have a much higher quantity of phosphorylated Mitf (discovered accidentally!).
So, stress signalling activates Mitf by phosphorylation (amongst other things), which gives rise to the activation of melanocyte stem cells (cells which still have the potential to differentiate into other types of tissue), but out of synchrony with the hair cycle. Hair of course is constantly lost and replaced, with the melanocyte being responsible for the pigmentation of hair. So, if melanocyte activation is out of sync with the hair loss/replacement (hair cycle), you get premature greying. Another side effect is the activation of quiescent (dormant/inactive) melanoma stem cells, giving rise to their proliferation. Over-stimulation of the proliferative (cell growth/division) pathways increases the likelihood of cancer in this case malignant melanoma.
Stress signalling can involve UV (too much sunbathing!) or other physical stress, including emotional stress, although the latter is still being investigated.
It seems that greys are much more likely to develop malignant melanomas. The reason is this. They have a mutation in the Mitf gene (MitfVIT), which increases the activation of Mitf, in the same way that stress does, so you have effectively twice the amount of stimulation and Mitf is continuously activated, as though the horses skin cells were under constant stress. In other words, in MitfVIT cells, the phosphorylation occurs regardless of whether or not stress is applied to the cell.
These are the horses which turn grey very early on in life. So, this dramatically increases the chances of a melanoma developing, when added to additional, environmental stimuli. I believe that this applies to greys that are born black I dont think it applies to chestnut born greys, as this is due to a different mutation, not directly connected to Mitf. I'm not clear on this bit, although I do know that chestnuts produce eumelanin, a variant of the normal melanin.
Flame_
Well-Known Member
Thankyou very much.
I wonder if anyone will ever be able to do anything about it, but I suppose that's the whole 'playing God' argument that goes with messing with anything to do with genetics.
Fransurrey
Well-Known Member
Who knows, KV8. The stuff I wrote was based upon human melanoma research, not horses, but I twigged when they started showing mice in the slides - mice that started out black and prematurely turned grey! I must stress that the above wasn't published - it's my theories based on what I've learnt.