What is a tumor?

[DonSchaeffer]

What is cancer? Do plants get cancer? I've seen a lot of plants with growth disorders where the organized structure of the cells is disrupted apparently by a disease. Could that be a plant version of cancer?

[apochronaut]

Humans obsess over such things , due to our outstanding focus on mortality.. Up until conventional religion lost it's stranglehold on the masses, faith held sway as the dominant guarantor of your future but now we seek answers to the unanswerable, expecting a response.

[Dennis]

Don,
I did a quick web search. You could look further-

Cancer is a disease in which some of the body's cells grow uncontrollably and spread to other parts of the body.

Like animal cells, plant cells mutate, but does that mean that they can develop cancer? In fact plants may not get cancer as we think of it, but they can and do suffer from tumors, where cells become disorganized and divide uncontrollably.

[DonSchaeffer]

Thanks guys. This is an interesting discussion. I guess it's a matter of definition. I was just speculating on the superficial similarity between uncontrolled cell growth when the "growth regulator" is turned off and the disorder of cancer and its uncontrolled growth properties.

[Leitzcycler]

https://en.wikipedia.org/wiki/Agrobacterium

[DonSchaeffer]

The argument is firmly put to close here: "Like animal cells, plant cells mutate, but does that mean that they can develop cancer? In fact plants may not get cancer as we think of it, but they can and do suffer from tumours, where cells become disorganised and divide uncontrollably." But I don't see the difference.

[Dennis]

Burls can be made into salad bowls by wood workers-

What Is a Tree Burl?

A burl is a bulbous, rounded tree growth usually found on tree trunks and sometimes on branches. Burls form as the result of stress that its tree has undergone.

Spalting is decorative in wood worked guitars or furniture-

Spalting is any form of wood coloration caused by fungi. Although primarily found in dead trees, spalting can also occur in living trees under stress.

[Dennis]

I think you are trying too much to compare or link humans to being like plants.

Much different.
You can't cut a person's arm off and stick it in the ground and grow another person. Stuff like that there.

[SuiGenerisBrewing]

The argument is firmly put to close here: "Like animal cells, plant cells mutate, but does that mean that they can develop cancer? In fact plants may not get cancer as we think of it, but they can and do suffer from tumours, where cells become disorganised and divide uncontrollably." But I don't see the difference.

This is not a simple topic.

In humans, cancers arise when one or more (usually more) genes that regulate cell division become mutated in a single cell, resulting in the onset of uncontrolled cell division. That higher rate of cell division makes the cell more likely to accumulate more mutations, meaning that over time the pre-cancerous cell will lose more and more of the features of a "good" cell - e.g. staying in its place in a tissue, having the proper structure, responding appropriately to growth and crowding signals, repairing its DNA, etc. At this stage the cancer cell is usually recognized by the immune system, which tries to eliminate the cancerous cell. This creates a strong evolutionary environment in which the cancer cells are continually selected for features like faster growth, neovascularization (the ability to force the body to grow new blood vessels), and immune evasion. Without these properties, a cancerous cell cannot form a tumour any larger than a pinhead, as the lack of blood flow and immune activity will keep it in check. Eventually, the accumulated mutations and changes in cell behaviour allows the cancer cells to form a large growth (a tumor), in which they predominate as the main cell type, and within which they control the immune response to prevent immune-mediated killing of the tumour. Severe cancers take on additional phenotypes, notably tissue invasion (cells of the tumour can leave the tumour and penetrate into the surrounding tissues) and metastasis (the cancer cells can move to new parts of the body via the blood or lymphatics). These two properties tend to go hand-in-hand and are usually what leads to fatal diseases in humans, due to the disruption of the function of multiple organs by invading cancer cells.

Because plant cells and immune systems are very different from our own, the tumour-forming process is quite different in them. Plant cells can become mutated in a way that causes uncontrolled growth, but everything else about their tumor-development process is different from that point on. Plant cells are very rigid and are generally not motile, and as such, processes such as invasion and metastasis are essentially impossible in them. Likewise, plants lack the "adaptive" immune response that people have which can identify cancerous cells as "foreign invaders". Instead, plants tend to recognize the damage caused by tumours to the neighbouring tissue, and respond by sealing that damaged tissue off from the rest of the plant. In some cases that is enough to prevent further tumour growth, leading to a small scar or mis-shapen portion of the plant. But like in humans, plant tumours can undergo pretty aggressive evolution and find ways to "force" the plant to send the tumour nutrients via inducing (or maintaining) the growth of xylem and phloem - the plant's equivalent of our circulatory system. In these cases, the tumours can become quite large (e.g. burles) and can eventually kill the plant if the tumours metabolic demands exceed what the plant can support, or in some cases, by physically weakening the plant leading to the plant to break.

Whether plant tumours qualify as cancer is more a matter of definition than of fact. Human and plant tumours share a number of features, including uncontrolled growth driven by mutation of the genes that regulate cell growth, and evolution of mechanisms which force the host to provide nutrients to the tumour. But a lot of the other aspects differ - immune evasion in plants doesn't see to occur, while it is a prerequisite in humans for cancer to form. Plants don't experience metatstasis, and even invasive disease is limited in plants to cases where a pathogen causes the cancer with invasion of the pathogen leading to invasion of the tumour.

[DonSchaeffer]

Very interesting. You are saying the disease process in plants is parallel and similar to cancer in animals. There is a difference in the way and extent the dysfunction spreads, but that is pretty technical. Is "cancer" generally recognized as a technical or scientific term, or just common usage?

[SuiGenerisBrewing]

Very interesting. You are saying the disease process in plants is parallel and similar to cancer in animals. There is a difference in the way and extent the dysfunction spreads, but that is pretty technical. Is "cancer" generally recognized as a technical or scientific term, or just common usage?

Cancer is a recognized and commonly used term when it comes to animals (including humans). Most other multicellular living things (e.g. plants and fungi) have equivalent diseases driven by mutation and a loss of control over cell division. But in those fields, AFAIK, they tend to not use the term 'cancer' and instead describe them as 'tumours', or by a name specific to that groups of organisms (e.g. galls in plants)

[DonSchaeffer]

People have gallstones. What are they?

[SuiGenerisBrewing]

People have gallstones. What are they?

Your gall bladder makes bile acids, which are chemicals that help digest your food. The bile acids normally pass through ducts in the gall bladder into the small intestine. Sometimes the bile acids can crystalize, forming a stone-like mass that blocks the bile ducts. That mass is the gallstone.

[DonSchaeffer]

thanks

[MicroPunter]

According to J. B. S. Haldane (British/Indian polymath), cancer is a funny thing. Personally, I didn’t find anything funny about it! But I did like Haldane’s poem:

I wish I had the voice of Homer
To sing of rectal carcinoma,
Which kills a lot more chaps, in fact,
Then were bumped off when Troy was sacked.
 
Yet, thanks to modern surgeon’s skills,
It can be killed before it kills
Upon a scientific basis
In nineteen out of twenty cases.
 
I noticed I was passing blood
(Only a few drops, not a flood).
So pausing on my homeward way
From Tallahassee to Bombay
I asked a doctor, now my friend,
To peer into my hinder end,
To prove or to disprove the rumour
That I had a malignant tumour.
They pumped in BaS04.
Till I could really stand no more,
And, when sufficient had been pressed in,
They photographed my large intestine,
In order to decide the issue
They next scraped out some bits of tissue.
(Before they did so, some good pal
Had knocked me out with pentothal,
Whose action is extremely quick,
And does not leave me feeling sick.)
The microscope returned the answer
That I had certainly got cancer,
So I was wheeled into the theatre
Where holes were made to make me better.
One set is in my perineum
Where I can feel, but can’t yet see ‘em.
Another made me like a kipper
Or female prey of Jack the Ripper,
Through this incision, I don’t doubt,
The neoplasm was taken out,
Along with colon, and lymph nodes
Where cancer cells might find abodes.
A third much smaller hole is meant
To function as a ventral vent:
So now I am like two-faced Janus
The only* god who sees his anus.
 
*In India there are several more
With extra faces, up to four,
But both in Brahma and in Shiva
I own myself an unbeliever.
 
I’ll swear, without the risk of perjury,
It was a snappy bit of surgery.
My rectum is a serious loss to me,
But I’ve a very neat colostomy,
And hope, as soon as I am able,
To make it keep a fixed time-table.
So do not wait for aches and pains
To have a surgeon mend your drains;
If he says “cancer” you’re a dunce
Unless you have it out at once,
For if you wait it’s sure to swell,
And may have progeny as well.
My final word, before I’m done,
Is “Cancer can be rather fun”.
Thanks to the nurses and Nye Bevan
The NHS is quite like heaven
Provided one confronts the tumour
With a sufficient sense of humour.
I know that cancer often kills,
But so do cars and sleeping pills;
And it can hurt one till one sweats,
So can bad teeth and unpaid debts.
A spot of laughter, I am sure,
Often accelerates one’s cure;
So let us patients do our bit
To help the surgeons make us fit.

(1964)

[DonSchaeffer]

Well done! That was one of the best science lessons I ever got.

[Polymerase]

Thanks to suigenerisbrewing for a very well written explanation. His answer is very informative, and I do not refute a single bit of it. However, I would like to clarify a few things about neoplasms. All disease in humans are either inflammatory, degenerative or neoplastic. Tumor growths are neoplastic, but not necessarily cancerous. Neoplasm is defined as follows:

“An uncontrolled replication of cells derived from a monoclonal cell line, that continues replication autonomously even after the cessation of the stimulus that provoked it.”

That is, a cell line from a single, abnormal cell, that has lost any regulation of it copying itself. How does this occur? All cells have sets of genes stimulating cell division (protooncogenes) and cells inhibiting division (tumor suppressor genes). In order for a neoplastic cell line to occur, mutations in both of these gene sets are required, so that replication is accelerated, and the machinery that normally stops an undue replication no longer functions as normal. When such a cell line is derived - remember it comes from one single mutated cell - a tumor will form. This tumor can either be benign, or malignant. Malignant neoplasms are cancers - there is no such thing as a benign cancer (but any tumor growth within the brain or skull cavity is dangerous, as it will displace brain tissue).

If a neoplasm merely grows, and does not invade the surrounding tissues, it is benign, and can usually be removed surgically. Tumors that invade surrounding tissues, are malignant, and disturbs normal physiologic processes, causing disease. This is cancer. Some of these tumor cell lines have the ability to spread (metastatasize) and form new tumors in others parts of the body. They are transported by means of hematogenous (blood-), or lymphatic (lymph-) routes, or by “seeding” in a body cavity.

As suigenerisbrewing pointed out, various signaling effects may derive from such cells, in order to stimulate blood vessel growth and suppress immune responses. Fast growing tumors may even outgrow their own ability to form new blood vessels, and thus exhibit a core of necrotic tissue. In general, neoplastic cells may keep, and even modify the traits of the tissues they derived from. The ability to promote blood vessel growth or inhibit immune responses are parts of normal functions, but may suppress the body’s ability to remove tumors, once the transformation has taken place. As tumors derive from the body’s own tissues, they are not recognized as foreign tissues, and thus tolerated by the MHC (major histocompatibility complex) - the “governor” of “friend or foe” to the immune responses. However, many transformed cell lines have changed to a degree where they elicit immune responses. This is higly variable between different cancers. Where normal tissue is damaged, inflammatory reactions will occur nonetheless.

This brings us to the concept of differentiation - and here’s what is interesting for a microscopist. The amount of change from the original cell type, defines to a large degree the severity of the cancerous disease. Some cells are very well differentiated. That means they are very similar to the tissues they derived from, and may share their properties. For instance, well differentiated tumours may produce glands or secrete hormones, perturbing the normal balance of the systems of the body. Such well differentiated tumors are growing slowly, and gives time to try various treatment options. Tumor cells with low differentiation are merely “generic” cells, and have no special properties apart from replicating. They do not form any functional tissues, but merely lumps of nonfunctional cells. These tend to grow very fast and aggressively. Alterations of the normal architecture of the tissues is a hallmark sign that some destructive process is going on. Seeing this combined with such atypiae as described above is very indicative of a cancerous process.

For the excited pathologist looking through the microscope, differentiation is key. Looking for atypiae, the degree of differentiation is key to diagnosis. Neoplastic cells show an array of changes, usually characterized by pleomorphism (the cells aren’t uniform in appearance), anisocytosis (variations in size) and hyperchromasia (excessive uptake of staining). Such cells usually have large, bizarre nuclei, staining very darkly, vary in shape and size, and may even lose the characteristics of their predecessors. Some well differentiated tumors will resemble the tissue they derived from. Poorly differentiated tumors may have no obvious features at all. The degree of differentiation, and the amount of infiltration of surrounding tissue are key parameters for evaluating severity. The presence of multipolar mitosis (cell division in more than two directions) are a sure sign of malignity, along with increased number of mitotic cells.

I know very little of plant physiology - but the basics of cell replication follow the same principles. Therefore, it would be highly unlikely not to see neoplasms in plants. How such changes alter the physiology however, is not my departement. But the principles governing development of the basis for neoplastic disease remain the same.

I hope this can add some clarity to the question.

[DonSchaeffer]

Crystal clear. Thanks a lot!

[Polymerase]

I’ve been puzzled by the question of why plants don’t seem to develop malignant neoplasms (cancer) like mammals do. Since I am on vacation, I have had time to take a superficial look into the matter.

While plants do develop neoplasms, the disorganized growth pattern of such mutated cells do not metastasize (spread) or cause severe disease (or at least usually don’t), but create local masses of disorganized tissue.

This seems to be due to the rigid structure of the cell wall, which I am sure many of you are aware of from studying plant sections, and some of you from gram-positive bacteriae and certain other prokaryotes. Mammalian cells do not have this outer structure - merely a bilayered phospholipid membrane with a hydrophobic core.

Forming tissues from walled cell populations, metastasis is unlikely to occur because of the tight junctions and adhesive properties of such a tissue. In controlling replication, such tissues also require a more coordinated control throughout the tissues, hence a single transformed cell would have less impact on the collective replication of the tissues, and would likely undergo apoptosis or pyroptosis (programmed cell death), rather than proliferate uncontrolled. Cell division in plants seem to be inherently coordinated through entire cell populations rather than on internal signaling of single cells, thus making the likelihood of a monoclonal cell line considerably lower. In addition, the rigid wall structure would restrict a cell’s ability to expand beyond its normal size without damaging itself and trigger apoptosis.

As such, the formation of a neoplastic tumour in plants would likely be more of a local problem than a comparable tumour in a mammalian cell line. However, I believe the metabolic requirements of a tumour could pose a problem to the plantks general health, just as malignant tumours in humans tend to alter metabolism and cause wasting (kachexia).


This article may be informative: https://www.jic.ac.uk/blog/controlling- ... et-cancer/

For those who can access it, this one is informative too: https://www.nature.com/articles/nrc2942

This one is interesting in understanding how plant tumours have been used to greater understanding of mammalian neoplasms: https://link.springer.com/chapter/10.10 ... -2736-3_12

In this regard, I also would like to mention the fact that cancerous cell lines have been of great benefit for research, as cell lines from cancer cells essentially are immortal. That means such a cell line can be used as a growth medium in research indefinitely, as it has no limits to its replicative potential. The most famous of such cell lines are HeLa cells, taken from a cervical cancer biopsy in 1951, and this cell line is still widely used in research today. Although we’ve had great benefit from these cells, the patient - Henrietta Lacks - unfortunately was not asked for permission to use her cells in research. This is highly unethical, and would not have occurred today.

[DonSchaeffer]

Why do plants differ from animals in this way? What do plants have that animals don't? Did I miss something--I didn't read your very informative text carefully enough. I don't have a good mind for this.

[Polymerase]

Why do plants differ from animals in this way? What do plants have that animals don't? Did I miss something--I didn't read your very informative text carefully enough. I don't have a good mind for this.

The most important virtue in this regard is not understanding, but being curious. In science, finding the right answers is subordinate to asking the right questions. Your question is a good one, although hard to summarize in a short, easily understandable note.

If we accept a common ancestor for all life forms, plants and animals separated a very, very long time ago. Although both organisms rely on sugar metabolism, their metabolism is fundamentally different, as plants are autotrophs, depending on light to metabolize their nutrients, while animals are heterotrophs, relying on consuming other organisms. Althouh both plants and animals rely on cellular respiration (the process of generating ATP from glucose), their approach to doing so is very different, as the energy generator organelle of plant cells are chloroplasts, while animals have mitochondriae. Describing these differences in detsil is too complex for this forum, and I do not have sufficient knowledge on botany to explain it properly. Of note, the human mitochondriae have their own circular DNA, which is believed to stem from a foreign microorganism that has incorporated into our cells at a very distant point in evolutionary history.

However, the differences discussed on the topic of neoplasms, are connected to the structural organization of cells and tissues. From the very origin of life, cells were protected from the environment by a physical barrier that would conditionally exchange ions or small molecules with the environment. Essentially, we were bags of potassium floating in a sea of sodium. Now, we have organized all these little bags of potassium (cells) as tissues, and taken the ocean (the sea of sodium) with us inside our organized tissues in the form of blood and interstitial fluid. How this correlates in plants is not known to me, but plants are also organized in tissues, and have complex mechanisms for maintaining fluid balance. Anyway, different strategies exist in making the boundary between cells and the outside environment. In mammalian cells, a phospholipid membrane is found, which is highly equipped with surface proteins facilitating exhange of various compounds. Plants have adapted a different concept, as the plasma membrane is surrounded by a much more rigid structure known as a cell wall. Both these strategies are seen in bacteria, where gram-positive species have a tough peptidoglycan cell walls, while gram-negative ones merely have a cell membrane with embedded lipopolysaccharides. Choosing the cell wall structure, tissues become much more rigid, and hence, the need for a more diffusely regulated proliferation occurs, as discussed in my previous post. These inherent differences - and a very long history of natural selection and adaptations make neoplasms behave very differently in mammalian and plant tissues, albeit the fundamental processes remain the same.

Remember, plants and animals have adapted to very different approaches to metabolism, and this has caused different traits to be selected, resulting in fundamentally diverse differentiation of tissues. For animals, mobility and temeprrature regulation is essential to maintain life. For plants, the ability to gather laege amount of sunlight, and absorbing nutrient from the soil, have selected large surface area of leaves and an extensive root network on the expense of mobility.

But basically, we rely on the same biochemistry, and thus are subject to many similar mechanisms of adaptation and pathogenesis.

I hope I am not causing your head to explode. Still being off work, I allow myself to proliferate in explanations that may be too detailed to be understandable….

[DonSchaeffer]

I love your explanations. Thank you for them. The trouble with me is I am stuck on the level of experience--why did nature bother with that? Can the chemistry of the "vegetable kingdom" support anything like that? Why does the animal kingdom--or any other kingdom--support that? When I say "experience" what am I talking about. I say the words and it throws me into a miasma where there is no longer a discussion. I have always been disappointed that we can't find the words to even describe consciousness in language that anyone understands. Sorry. I lapse into dreams.

[Polymerase]

I love your explanations. Thank you for them. The trouble with me is I am stuck on the level of experience--why did nature bother with that? Can the chemistry of the "vegetable kingdom" support anything like that? Why does the animal kingdom--or any other kingdom--support that? When I say "experience" what am I talking about. I say the words and it throws me into a miasma where there is no longer a discussion. I have always been disappointed that we can't find the words to even describe consciousness in language that anyone understands. Sorry. I lapse into dreams.

Dreaming is the basis for all science, in my opinion. If we cannot dream, we cannot question our existence, and we would not bother to find out anything anout our exostence and surroundings. Keep dreaming. Keep asking. Keep trying to understand.
Without dreaming, I would probably be a despiccable accountant somewhere. I am a child, and easily fascinated by my surroundings. Scientists are essentially just children with a lot patience.
Att some point however, our questions need to be put under systematic scrutiny, so that we can see beyond the limits of our own senses. Only by doubting everything, can we understand anything at all. Nothing is ever proven to be true - it is merely concluded as the most likely cause of what we observe. That means any data that perturbs our current understanding must oblige us to rebuild what we thought we knew. And that, my friend - is the beauty of science. It is bereft of emotions and personal beliefs. It is just a systematic way of connecting observations to a greater approach towards the understanding of our very existence.

But the scientist himself, is allowed to be passionate. I would like to share with you the beautiful statement made by Marie Curie in 1933:

“I am among those who think that science has great beauty. A scientist in his laboratory is not only a technician: he is also a child placed before natural phenomena which impress him like a fairy tale. We should not allow it to be believed that all scientific progress can be reduced to mechanisms, machines, gearings, even though such machinery also has its beauty.

Neither do I believe that the spirit of adventure runs any risk of disappearing in our world. If I see anything vital around me, it is precisely that spirit of adventure, which seems indestructible and is akin to curiosity. Without the curiosity of the soul, what would we be? This is the beauty and nobility of science: the desire to pursue the frontiers of of knowledge, to trace the secrets of matter and of life, without any preconceived idea of the eventual consequences thereof.”

These words - in the original french version - adorn the door to my lab, constantly reminding me every day of why I find purpose in being alive.

Never stop dreaming. Never grow up!

[DonSchaeffer]

The trouble is it hurts. It's bothersome. It makes enemies and causes unrest. Thank you fellow traveller.

[Polymerase]

The trouble is it hurts. It's bothersome. It makes enemies and causes unrest. Thank you fellow traveller.

It resembles life, that is….

[DonSchaeffer]

Yes! We should stop building air tight walls around science.

[Polymerase]

Yes! We should stop building air tight walls around science.

Are there any walls around science? I don’t quite understand your position….?

[DonSchaeffer]

There are limits to what we can study. Logic and rationality are very limiting, people get uneasy if we deviate too far. I think the answers may be outside of those limits. It may not feel safe all the time.

[Polymerase]

There are limits to what we can study. Logic and rationality are very limiting, people get uneasy if we deviate too far. I think the answers may be outside of those limits. It may not feel safe all the time.

I tend to disagree. There are limits as to what science can investigate. It is not about discomfort. The only real “wall” I can think of, is funding. There are two major obstacles for science today:

1) More and more research is being funded by commercial interests. This puts unhealthy conflicts of interest forth, and may affect what knowledge is produced. Not to say that wanted results are being manipulated into place, but necessary research with no immediate financial interest is being suppressed by corporate funding. Universities essentially do not exist any more.

2) The search for acknowledgement leads to a lot of academic theft. That implies that the open discussion among scientists no longer occurs, and much is lost by the selfimposed restrictions on free discussion.

In addition, obscure open access publications florish. Anyone can publish anything. They claim to be peer reviewed. They are not. They are fueled by the money of young scientists hoping to expand their publication history. Finding reliable sources is increasingly difficult.

And finally, a growing malignancy are the conspiracy theorists. People these days tend to think that they are as knowledgeable as nobel laureates because they’ve watched a few videos on youtube. Authority is no longer recognized. Unemployed Joe knows more about genetic material than Watson and Crick. In his mind their knowledge is outdated, and he has read a post on twitter from a doctor who claims cancer is a fungal infection. (But he never read their 1953 paper, and he has no idea how DNA is organized and replicated. He thinks mRNA is a poison imposed on us from a government lab…)

Conspiracists are an unrecognized threat to humanity. They can perturb society completely unless we stop their disinformation campaigns.

[DonSchaeffer]

Onward and upward! I appreciate your upwardness. There is a lot of real mystery out there. We don't yet even have the language to describe critical parts of it. I am confident you guys will find it.