Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: BetaAmyloid on October 23, 2009, 11:40:24 PM
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I was thinking about what causes cancer. Everything that causes cancer causes a mutation in a cell's DNA - yet people say that if we injected a cure the whole body would completely shut down since all the cells would react to the medicine since all have the same DNA.
But, if cancer alters DNA in some way (which I'm not sure if we have discovered exactly what yet), then could we not attach a radioactive tracer to cells of which have the altered sequence followed by a cure that is attracted to this radioactive tracer?
--Correct me if I'm wrong--
Thanks,
The Cancer Curer
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A few points:
1) It is very difficult to target DNA because DNA is well protected inside of the cell. Thus, both the tracer and the therapy recognizing the tracer would likely have to be designed to pass thorugh the cell membrane and access the nucleus (not a trivial thing to do).
2) There are many different types of mutations to the DNA that can cause cancer and not all mutations cause cancer (actually it's more complicated than this because although one mutation might be associated with cancer [e.g. mutation of p53], it is often not sufficient to cause cancer unless other mutations are present).
3) Even though we know some genes that are very frequently mutated in cancer (e.g. p53 is mutated or deleted in over 50% of all cancers), these mutations do not result in the same altered sequence, so it would be difficult to design a therapy to target all p53 mutations. Such therapies, if we could get them to work, would likely work only on a single individual or a small group of individuals.
4) This strategy has been thought of for the treatment of cancer, albeit in a slightly different form. Sometimes cancer cells, by virtue of being in a different state than other cells, will display different proteins on their plasma membrane than normal cells. These proteins, referred to a biomarkers, can be used to distinguish between normal and cancerous cells and target drugs specifically to cancer cells. Because these biomarkers would reside on the outside of the cell, they are much easier to target than intracellular targets. The tricky part is identifying these biomarkers (if they exist for a particular cancer) and ensuring that they mark the entire tumor and are specific only to the tumor.
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In response, to cause an informative debate for my knowledge and to spark thoughts of others:
1) Could it be possible that we develop, or understand, what types of molecules penetrate through the multiple "protectors" of the DNA, so that we are able to reach the DNA (As a start) and then correct the sequences? (Symbolically, such as a reverse definition, working from the definition to find the word, instead of looking up the word to find its definition.)
2) --No debate--
3) Could it be possible that we develop a type of cure that does not search for a sequence, but search for a specific molecule or compound that most of the time causes the mutation in a cell's DNA? Instead of looking for ATTAGGCC, the cure would look for the actual mis-print in Adenine itself.
4) I agree, yet I think (by opinion, not through experimentation) that the destruction of a cell would be much more subtle and controlled from the inner parts of a cell rather than the outer parts of the cell, since it could cause destruction among other cells besides the cancerous cell itself. (Symbolically, it would be better and more controlled to destroy a building with detonators from the inside rather than from the outside, since it would harm the other buildings around it.)
Thanks,
The Cancer Curer
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In response, to cause an informative debate for my knowledge and to spark thoughts of others:
1) Could it be possible that we develop, or understand, what types of molecules penetrate through the multiple "protectors" of the DNA, so that we are able to reach the DNA (As a start) and then correct the sequences? (Symbolically, such as a reverse definition, working from the definition to find the word, instead of looking up the word to find its definition.)
We know what factors are necessary to get cytoplasmic molecules into the nucleus and we know some methods to get molecules from the outside of the cell into the interior of the cell. We don't have something to recognize incorrect sequences and correct them. In general, molecules that are able to recognize specific sequences of DNA are very complex and difficult to get inside of the cell, but once they are inside it is not difficult to target them to the nucleus.
3) Could it be possible that we develop a type of cure that does not search for a sequence, but search for a specific molecule or compound that most of the time causes the mutation in a cell's DNA? Instead of looking for ATTAGGCC, the cure would look for the actual mis-print in Adenine itself.
Once a mistake has been copied into a new strand of DNA, the mutated nucleotide is indistinguishable from any other nucleotide in the genome (unless you have some way of comparing the new sequence to the original sequence). There are specific types of damage to the DNA (e.g. thymine dimers, 8-oxo-guanine, cytosine deamination) that cause mutation, but the cell does have mechanisms for recognizing these lesions and correcting them. Often, cancer cells are deficient in DNA damage repair and cannot correct these lesions, so some artificial means of helping the cells fix these lesions could possibly help prevent cancer.
4) I agree, yet I think (by opinion, not through experimentation) that the destruction of a cell would be much more subtle and controlled from the inner parts of a cell rather than the outer parts of the cell, since it could cause destruction among other cells besides the cancerous cell itself. (Symbolically, it would be better and more controlled to destroy a building with detonators from the inside rather than from the outside, since it would harm the other buildings around it.)
It depends how you are killing the cell. Methods based on heating the cells with nanoparticles or radiation will still damage neighboring cells regardless of whether the anti-cancer agent is intracellular or extracellular. Drugs targeting specific proteins can be designed to act only on the cells that they are targeted to whether they act intracellularly or extracellularly.
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We know what factors are necessary to get cytoplasmic molecules into the nucleus and we know some methods to get molecules from the outside of the cell into the interior of the cell. We don't have something to recognize incorrect sequences and correct them. In general, molecules that are able to recognize specific sequences of DNA are very complex and difficult to get inside of the cell, but once they are inside it is not difficult to target them to the nucleus.
If you are able, could you direct me to a site that may explain or list what factors allow entrance and exit through the cytoplasmic molecules?
Once a mistake has been copied into a new strand of DNA, the mutated nucleotide is indistinguishable from any other nucleotide in the genome (unless you have some way of comparing the new sequence to the original sequence). There are specific types of damage to the DNA (e.g. thymine dimers, 8-oxo-guanine, cytosine deamination) that cause mutation, but the cell does have mechanisms for recognizing these lesions and correcting them. Often, cancer cells are deficient in DNA damage repair and cannot correct these lesions, so some artificial means of helping the cells fix these lesions could possibly help prevent cancer.
So, does DNA differentiate between cells, or is there a general pattern to the DNA (between cells)?
It depends how you are killing the cell. Methods based on heating the cells with nanoparticles or radiation will still damage neighboring cells regardless of whether the anti-cancer agent is intracellular or extracellular. Drugs targeting specific proteins can be designed to act only on the cells that they are targeted to whether they act intracellularly or extracellularly.
When creating a drug, is it usual to create the drug to attach to a protein to destroy the cell, or are there possibilities of creating a medicine (drug) that attaches to other things, such as a cholestorol, hormone, or the phospholipid bilayer itself?
--Please let me know if I am being a pest, I'm not sure if you read my introduction in the other areas, but I'm 17-years-old and I'm trying to create a trilogy that discusses cancer and a theoretical prevention or cure to it. The only way I know of learning is by asking questions, but I don't want to ruin this by asking too many questions.--
Thanks,
The Cancer Curer
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If you are able, could you direct me to a site that may explain or list what factors allow entrance and exit through the cytoplasmic molecules?
http://en.wikipedia.org/wiki/Nuclear_pore#Transport_through_the_nuclear_pore_complex
So, does DNA differentiate between cells, or is there a general pattern to the DNA (between cells)?
I'm not quite sure what you mean here. Are you asking whether different cells within an organism have differences in their DNA? If so, the answer is yes, because of mutations. The differences are small, but can be significant (i.e. when a cell becomes malignant).
When creating a drug, is it usual to create the drug to attach to a protein to destroy the cell, or are there possibilities of creating a medicine (drug) that attaches to other things, such as a cholestorol, hormone, or the phospholipid bilayer itself?
Most drugs are targeted to bind proteins. It would probably be difficult to design a drug to bind a small molecule (the drug would likely have to be fairly large in order to bind the molecule with high specificity). Also, many of these small molecules are in very high concentrations, so you would need high levels of drug to bind to them. You can however, fairly easily design molecules to bind to phospholipid bilayers.
--Please let me know if I am being a pest, I'm not sure if you read my introduction in the other areas, but I'm 17-years-old and I'm trying to create a trilogy that discusses cancer and a theoretical prevention or cure to it. The only way I know of learning is by asking questions, but I don't want to ruin this by asking too many questions.--
It's no problem. Asking questions is the best way to learn. That's what this website is here to do: answer questions from curious students. Since you are interested in cancer, might I suggest reading the ariticle, "The Hallmarks of Cancer" by Hanahan and Weinberg (available at http://biotech.biology.arizona.edu/New%20Images/hallmarks_of_cancer.pdf)? The paper does a good job of categorizing the different types of mutations required in order for a cancer to develop, and describing the relevant biology involved.
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Thanks, covered all my questions - I'll start a new thread if I have more questions (which I will) so I won't travel off topic.
Thanks,
The Cancer Curer