27 November 2009

Against melanoma – vaccine-implant

An implanted pill will get rid of skin cancer
Alexey Tymoshenko

Scientists from Harvard University have developed a method capable of destroying cancerous tumors. A disk made of porous plastic, impregnated with a vaccine and implanted under the skin, gave good results on experimental mice, in which it was possible to eliminate both the tumor itself and its metastases.

The experiment was performed on rodents with a malignant skin tumor. Melanoma, skin cancer, is considered one of the most dangerous types of malignant formations in humans due to the increased likelihood of metastasis formation.

Why an implant?

The authors of the new method in a press release from the university talk about why it was necessary to implant a disk with a medicine under the skin and what the medicine was. According to scientists, a porous tablet with a diameter of 8.5 mm was impregnated with a mixture of two substances – cytokines and tumor antigens.

The picture shows an implant next to a dime
and a cross-section of the polymer matrix, in the cavities of which the cells of the immune system are "trained" on tumors.

Cytokines are molecules that activate cells of the immune system. And tumor antigens, in turn, allow T-lymphocytes to choose a target to be destroyed. Thus, the tablet embedded under the skin does not destroy the tumor itself, but leads the immune system to it. In fact, we are talking about a cancer vaccine, only with a somewhat unusual method of injection.

A tablet under the skin, made of plastic that resolves over time (such materials are called biodegradable by doctors), maintains the activity of lymphocytes fighting tumor cells at a constant level. In this way, it compares favorably with injections and ingestion of drugs: as the researchers note, with the traditional introduction of activated and tumor-fighting cells into the body, 90% of the injection was wasted.

Why didn't they do this before?

Non-toxic porous plastic, capable of disintegrating into harmless components over time, has been known before. Moreover, in the USA its use for medical purposes is approved by the FDA. Scientists also knew about the role of cytokines and tumor antigens. But why is it only now that we are talking about testing such a tool, and even then only on mice?

The problem is that the immune system is formed not only by lymphocytes of the same type, which track down and destroy tumors. There are many different types of cells that perform different functions. Scientists have managed to create an implant that includes so-called dendritic cells. It is they who transmit information about the tumor antigen to the lymph node closest to the implanted tablet, from where other cells, T-lymphocytes, come out.

T-cells are also different: and one of the species bears the formidable name of T-killers. The destruction of tumor cells occurs with the participation of "killers" who, when confronted with a cancer cell, recognize it by the characteristic proteins on the surface (the "knowledge" about which proteins to look for was obtained by them in the lymph node). After the tumor cell is identified, the T-killer either sends a biochemical signal triggering the cell's self-destruction, or releases a substance that damages the target membrane, or uses a combination of these methods.

Since the pill that activates the immune system and forces it to produce tumor-oriented T-killers is constantly in the body and one T-cell is replaced by another, the cancer tumor has no chance of further existence, much less development.

The prospects

So far, scientists speak cautiously about transferring the technique to the clinic. Probably, in the future, the vaccine disk will be implanted under the skin and used in combination with other cancer treatment methods. David Mooney, one of the authors of an article published in the journal Science Translational Medicine (Omar A. Ali et al., In Situ Regulation of DC Subsets and T Cells Mediates Tumor Regression in Mice), says that theoretically their development will be more effective than previously tested methods in clinics, but the final conclusion, of course, it will follow only after appropriate tests.

Portal "Eternal youth" http://vechnayamolodost.ru27.11.2009

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