I am not talking about chemotherapy or radiotherapy. So, if it exists, what is the best biological technique to cure cancer as of now?
closed as primarily opinion-based by rg255, kmm, anongoodnurse, AliceD♦, MattDMo May 11 '16 at 21:10
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There is no general therapy for cancer - as there is no general cancer. Cancer is the umbrella term for a disease where you have body cells growing without control, leading eventually to death. But since there is a wide variety of cells in the body, there is also a very wide variety of different cancers.
To treat these, surgery is often the first line of therapy. For some cancers this is already sufficient to cure the patient, examples are skin cancers (not only melanoma but the other forms as well) where you can cure a very high potion of the patients. This only works for early forms of the cancers when there are no metatases present.
Besides this, additional therapies are used - as you said yourself chemotherapy in the different forms as well as radiation therapy. Chemotherapy is given systemically and targets fast growing cells (cancer cells have these properties) and causes mutations or other problems which let the cancer cells eventually die. Radiation works with the same principle, but is more focussed.
Relatively new therapies are the targeted therapies where the treatment uses the occurance of certain common mutations. An example would be the mutated BRAF kinase in melanoma (and also in a number of other cancers) which can be specifically inhibited with an inhibitor. This avoids a lot of problems general adverse effects of the drugs. Additionally immune therapies are also new which use antibodies against surface receptors of T cells to prevent their inactivation. These T cells then attack the tumor.
These are all non-biological treatments. More biological ones are modified oncolytic viruses. In this therapy you inject genetically modified viruses which preferrably infect the tumor and then destroy it. These are relatively new, but an interesting option. See references 1 and 2.
An old method is the usage of bacteria to treat tumors - the first obervations on this where done in the late 19th century, see reference 3 for more information and a lot of further references.
A number of the chemotherapeutic drugs used today are originated from nature, but are today synthesized and used in a pure form and not isolated from their origin anymore. Examples would be vincristine, irinotecan, etoposide, and paclitaxel. See references 4 and 5 for details.
Besides this, there are no effective "natural" cancer cures, despite the claims of several "alternative medicine people". These are either based on wrong assumptions of biology or wrong ideas like Homeopathy.
I'd like to vouch for adoptive cell transfer therapy, ACT, using tumor-infiltrating lymphocytes, TIL (Lee & Margolin, 2012). While the therapy is currently geared largely for metastatic melanoma, there are investigative studies involving TIL ACT in other cancers such as head/neck, cervical, ovarian, breast, etc. I want to note immediately that this is not a cure but rather a promising treatment.
The idea is that T cells have recognized a tumor antigen and become activated toward the tumor. They extravasate to the tumor and attempt to kill it, but they become overwhelmed by evasive tumor mechanisms and the tumor environment. So they're just kind of there, with the tumor, ready to fight but too tired to finish the job. Hence, tumor-infiltrating lymphocytes.
The patient will have an accessible tumor excised by a surgeon, where a technician will cut the tumor into small fragments. The fragments are incubated with media and IL-2 in a way that skews the growth toward lymphocytes. And so from the same patient we'll take some blood, and separate the PBMCs, and then irradiate them. The irradiated "feeder" cells provide to the lymphocytes co-stimulatory signals that promote their growth. We also incubate the T cells with an agonistic monoclonal antibody OKT-3 that activates CD3 on the T cells. And so with this, the T cells rapidly expand over the course of a couple of weeks to several billion cells. Importantly, we should have a good population of CD8+ T cells that are tumor-reactive.
The patient, before re-infusion of their own T cells, undergoes lymphodepletion with the drugs cyclophosphamide and fludarabine. The point is that immune responses are heavily regulated, and so you want to get rid of T-regs, and other immune regulatory cells that might blunt the effectiveness of the TIL. You also figure, you're infusing several billion cells, you need to make room for these extra immune cells. The T cells should then in theory find every tumor with the antigen they were programmed for initially and kill them with granzymes, perforins, etc.
There are some barriers to the treatment, the first being that it's largely exploratory and thus not widely available. Due to the complexity of the treatment, it's also very expensive (at the NIH, $500,000 USD perhaps?). You must also consider that while we're growing these TIL, there's a patient dying on the other end that may not make it to the treatment phase. There are stochastic issues that also prevent the treatment from reaching it's maximum potential.
The first is the tumor: they exhaust the T cells quite a bit, and in T cell exhaustion you get an abrogation of the T cell mechanisms, and so our fight becomes bringing these TIL back from the dead:
Source: T Cell Exhaustion
For example: The presence of the T cells also sometimes cause the tumor to begin expressing PD-1L, ligand to a programmed death receptor PD-1 that T cells up-regulate in exhaustion. Through SHP-2, PD-1 blocks stimulatory signal 1 to T cell activation at ZAP70. The tumor microenvironment is also very acidic, and the T cells take issue with this and it blunts development. Because of this, when you're growing T cells out of the tumor fragments, sometimes you get a bad yield, and the way you actually cut the fragments, or how the surgeon excised the original tumor play a part in manufacturing the cancer treatment. You can have a patient that might respond well to TIL, but end up they just don't grow out of the tumor.
And so research is focused on getting the T cells to grow better, making the tumor less stubborn, and reducing the noise caused by these stochastic effects that aren't at the moment in much control of the scientist. You can also make note that while TIL ACT is largely a biological therapy, you still need chemo as a crutch to achieve optimum efficacy, hence the cyclophosphamide/fludarabine immunodepletion.
PS I tried to cover everything but we can go deeper and deeper with this therapy so I wanted to keep it brief, but this means I may also miss some critical notes, so I'm available to clarify things if need be.