RK and Senna's Research Proposal

Topic
Breast Cancer Drug Delivery

Background
Mammaglobin is a sensitive marker for breast carcinoma

Mammaglobin is a protein expressed in the surface of breast cancer cells. About 80% of breast cancer cases were associated with a detectable level of Mammaglobin. Currently, Mammaglobin has been utilized as a sensitive breast cancer detection in humans (using RT-PCR to detect expression of Mammaglobin) (Marques et al. 2008). Studies have also shown positive immunohistochemical reaction for Mammaglobin in 78.72% of human primary breast carcinoma and 58.02% cases with lymph node metastasis (Raica et al., 2009).

These findings have raised two questions:
 * 1) Can we utilize this specific marker to target chemotherapy drugs to breast cancer cells?
 * 2) Can we use this specific antigen induce the body's immune response to breast cancer?

Utilizing Mammaglobin as a marker for drug delivery Zuo et al. provided a solid evidence that Mammaglobin is associated with the membrane of Breast carcinoma. They also engineered a nanoparticle consisting of an LDL molecule containing doxorubin (a cytotoxic drug) conjugated to the antibody to mammaglobin. This in vitro study showed that this nanoparticle was successful in targeting breast cancer cells. In addition, the nanoparticle binds to and specifically lysed breast cancer cells only.

This research was exciting and we look forward to engineer our own drug-delivery nanoparticle utilizing mammoglobin. However, we might be interested in in vitro study, maybe using a humanized mouse (BLT mouse that has the immune system similar to humans) to test our nanoparticle. We then proceeded to research for current drug delivery technologies for cancer.

Other existing technologies for cancer drug delivery
 * 1) Arap et al., 1998

This used in vivo phage-displayed peptide libraries to screen for a peptide that binds to tumor cells. They found a peptide that binds to human breast carcinoma (CDCRGDCFC, termed RGD-4C). They couple the peptide to doxorubin and administered it to mice. They found that the mice that received treatment had significantly smaller tumor burdens. In addition, treatment with doxorubin coupled with RGD peptide showed less toxicity to liver and other organs, as compared with treatment with free doxorubin, suggesting that this drug-targeting was successful.

This article further convinced us that a drug coupled with a binder to an antigen in breast cancer cells would result in a specific cytotoxicity.


 * 1) Poste and Kirch, 1983

This articles reviews the current pros and cons of the various methods of drug delivery. From this paper, we got knowledge about what we should consider should we want to engineer our own drug-delivery mechanism.

- Antibody-coupled drugs are limited by stoichiometry (the Kd or binding strength of the antibody to the markers) and the antigen concentration at the exterior of the cells. In addition, we have to make sure that the antibody does not cross-react with other cells (that the antigen does not exist in normal cells), or there will be a non-specific cytotoxicity. Lastly, one would have to make sure that the antibody-drug bond strength is such that it's strong enough to not dissociate in blood (and kill other cells on the way) but can be broken once it is on the site so it can be released into the cell.

- Some other method to kill cancer is by administering lymphokines to stimulate macrophage activation. This lymphokines can be enclosed in a liposome. This idea made us think about ways to stimulate T-cells using the mammaglobin-specific activation.

- Finally, they noted that liposome are shown to be retained longer in lymph nodes, which means that an efficient way to treat cancer metastases inside lymph node is by using lipid layers to enclose the drug.


 * 1) Ruoslahti et al, 2010

This review noted that most drug delivery utilizing tumor surface marker was effective only to kill the cells in the periphery of the tumor mass, but not the cells inside the core. This can lead to drug resistance. Furthermore, they noted that the vascularization in tumor mass are different than the rest of the blood vessels in our body. This induces interest for us because we might find another antigen specific to blood vessel in tumor mass and we would be able to deliver the drug particles into the tumor mass, too.

Ruoslahti et al had also found a tissue-cell penetration peptide sequence of the motif "R/KXXR/K". This motif can me combined with any peptides that are shown to have affinity to cancer cells, then be conjugated with a drug. This conjugate would make the drug to be specifically uptaken into tumor tissues. In addition, this conjugation increases the tumor uptake of the cancer cells. This motif also induced our interest; we might conjugate a drug with this motif and see if it works too.

Research Ideas
We are currently looking into two research ideas. The first idea is to use mammoglobin as a target for drug delivery nanoparticles. Nanoparticles have been produced that successfully targetted mammaglobin presenting cells through mammaglobin binding antibodies (Zuo et al). We suggest modifying such nanoparticles by adding sequences that are known to penetrate tumors (similar to Ruoslahti et al.'s findings) which would enhance the nanoparticles ability to bind to the cancer cells and be uptaken by the cells.

The second idea is based on immunotherapy. We suggest that nanopaticles with mammaglobin recognizing antigens be used to release immuno-stimulating compounds which cause an increase in presentation of mammaglobin in antigen presenting cells. If we can increase the antigen presentation in early stages of breast cancer and activate early immune response, we hope to see a better tumor clearance by the immune system.