Re: Would this help to prevent cancer in people?

My answer is a resounding yes! Combating cancer through modulating the immune system (a.k.a. cancer immunotherapy) really is the wave of the future. Although tumors themselves are not foreign to the body and thus often invoke immune tolerance, with proper costimulation and a strong T (and ideally NK) cell response, the immune system can focus on the few antigens that might arise from self proteins that are mutated, overexpressed, and/or misprocessed. These antigens need to make their way to the draining lymph nodes so they can be presented to T cells by antigen presenting cells (APCs) such as dendritic cells, that would then traffic to the tumor site and either kill tumor cells directly or secrete factors that recruit other cells to do so. I don't want to sound like a gung ho warmonger, but a good military analogy is that of using the FBI to root out members of a homicidal organization blending into society. Once they are interrogated, the agency can then recruit other arms of the military to mount a full scale assault on their home base.

The way tumors are treated traditionally is through surgery and toxins (chemotherapy) which target growing cells. Surgery resembles a cruise missile strike in that despite the accuracy and skill of the surgeon, some tumor cells that are not visible can still escape and set up shop elsewhere. These survivors often become more vicious after having been targeted (different biological rationales exist for this finding, like escape mutants, or extracellular matrix destruction). On the other hand, chemo is like dropping a nuke on the battlefield- very effective in destroying the enemy, but also kills friendly fighters and bystanders in a large area. Often in treating human tumors, downstream lymph nodes are surgically removed. There is some debate regarding this, since as mentioned above lymph nodes serve as a launching pad for anti-tumor responses and hence taking them out is akin to destroying an entire castle for fear of having it taken over and used as a base by the enemy.

From all these pithy analogies, it can be appreciated that current mainstream treatments for cancer leave much to be desired, although they have saved millions of lives over the last 3-4 decades of use. Immune-based therapies also have their drawbacks, namely that too strong a response to tumor tissue often results in healthy cells also being targeted, resulting in mild to severe autoimmunity (ie. vitiligo from anti-melanoma treatment). Future advances can ideally reveal how to precisely control the activity of immune cells and better focus their cytotoxic potential.

I have focused on tumor treatment here rather than prevention as stated in the original query, but similar considerations apply since the body is thought to continually deal with small outbreaks of cellular growth, and decreased immune function has been shown to lead to more tumor formation (ie. Kaposi's sarcoma in AIDS patients). When our immune systems eliminate these outbreaks, we are not usually aware (perhaps a slight pain, fever, lethargy?) of what is going on, but it happens just the same. Notwithstanding tumor-prone genetic backgrounds, keeping the immune system strong, especially in later years of life, will certainly lower the chance of aberrant cells establishing a solid mass or traveling beyond their tissue of origin (metastasizing).

To summarize, the three major arms of any immune-based treatment ought to be:

1) A cancer vaccine containing specific antigens found in the targeted tumor.
2) A way to stimulate antigen presenting cells (ie. adjuvants, TLR ligands, GM- CSF)
3) A way to promote T cell activation and expansion (ie. cytokines, anti-CTLA- 4)

One would predict that the best results would ensue from a combination of these treatments, specifically tailored to the patient's tumor and genetic background. We are not far from delivering this type of medical treatment. The future holds much promise as long as support for basic science is strengthened so we can do more experiments to learn about how these cells interact at a cellular and molecular level.