Essay: The Drake Lab: A Brief Novella

The Drake Lab: A Brief Novella
Background:
Prostates cancer is the uncontrolled growth of the prostate, capable of eventually metastasizing, or spreading to areas outside the prostate. This cancer is responsible for the death of 30.6 out of 100,000 men in the European Union^1. A type of hormone, called androgen, is responsible for the growth of the prostate, and in turn, the growth of prostate cancer. Androgen binds to the androgen receptor in the hypothalamus of the brain, stimulating the growth of another hormone that travels to the pituitary gland. The pituitary gland then releases another hormone that travels down to the testes, leading to the production of testosterone. Testosterone then enters prostate cells and is changed by an enzyme, forming dihydrotestosterone. This hormone binds to the androgen receptor in the cell and activates transcription for genes that promote cell growth^2.
Different therapies can be used to prevent androgen from reaching the prostate, including surgical and medical castration. With these therapies, the flow of androgen from the testes to the prostate is cut off, subsequently preventing further growth of the prostate cancer. In surgical castration, the testes are removed to prevent testosterone from being formed. In medical castration, drugs are administered to reduce the production of testosterone. Studies have shown that this leads to a decrease in prostate size, but not the size of the tumor ^2.
Over time, some patients have renewed growth of the prostate cancer despite a lack of hormones reaching the prostate. This is called castration resistant prostate cancer, or CRPC for short. In CRPC patients, the androgen receptor is over-expressed and behaves as though it is activated^3. The reason for this behavior is unknown, although research has shown that tyrosine kinase activation may play a role^4. Tyrosine kinases are involved in intercellular activities in an organism, including signals for cell growth, adhesion, and death. Tyrosine kinases have highly conserved domains in their sequences, making is easier to identify them and their variants^5.
Bone metastases occur in 90 percent of patients with prostate cancer, and these patients are the ones who suffer from CRPC. Despite the many genetic alterations that occur during metastatic prostate cancer, kinases rarely have mutations in the live cell^6. In addition, kinase activity appears to be due to pathway activation within the tumor^7. This includes the coexpression of wild-type SRC kinase and androgen receptor, as well as other tyrosine kinases such as ABL1 and Janus kinase 2. Tumors from metastasized CRPC have been shown to have similar features, indicating similarity within the single patient. Comparing these tumors across multiple patients has shown differences between them, indicating the need for personalized treatment^7.
Phosphorylation of tyrosine kinases indicated a change in behavior^8. Using quantitative mass spectrometry (MS), phosphorylation patterns in tyrosine found in 16 autopsied metastatic CRPC tissues were measured across 13 patients^7. Also included in the MS were samples from cell lines, that were responsive to androgen (22Rv1) and were not responsive to androgen (LNCaP). Hundreds of unique phosphopeptides and proteins were identified and analyzed using phosphoproteomics, revealing distinctly different behavior in cell line-derived samples compared to autopsied tissue (Fig. 1A). Further, the phosphorylation of tyrosine kinases in cancerous and noncancerous prostates were relatively similar, suggesting a role in CRPC growth^7 (Fig. 1A).
Metastatic cancer samples showed similarity in phosphoproteomic patterns across multiple organ sites (Fig. 1B). This was determined through research on samples from the lung, prostate, liver, and brain. Using activated kinases, a Western blot was performed and showed unique phosphoproteomic patterns for each patient, suggesting unique behavior in each patient^7 (Fig. 1C).
Figure 1: Phosphoproteomic analysis of cancerous, noncancerous, and cell line-derived prostate cells. (A) Comparing phosphoproteomic clustering of cell line-derived cancer cells, noncancerous cancer cells and cancerous cells. (B) Evaluating phosphoproteomic similarity between metastatic samples from the same patient. (C) Western blot of multiple kinases across multiple patients, showing unique phosphoproteomic patterns.
Further analysis of kinase activity within each individual patient was performed using 28 different metastatic lesions from 7 CRPC patients. Using proteins identified from MS, a Western blot was performed and showed different kinase activation patterns in each patient (Fig. 2). Moreover, it was shown that metastases from the same patient exhibit similar kinase activities, suggesting that they are unique to that patient^7.
Figure 2: Western blot analysis of kinases from multiple anatomical locations from the same patient. Each patient showed similar kinase activity, regardless of where the sample was from.
Understanding the impact unique activation patterns of CRPC in individual patients is important to determine a potential treatment. After combining the identified kinases, their predicted activities, and potential inhibitors, dasatinib, a SRC inhibitor, and trametinib, a MEK inhibitor, were predicted to provide beneficial therapy to metastatic CRPC patients if combined^7. Targeting protein tyrosine kinases has provided clinical advances and increased patient survival, as they are highly involved in cancer growth^9.
Objectives:
The goal of the Drake Lab is to understand the mechanisms through which castration resistant prostate cancer progresses and how to better treat patients suffering from the disease.
The Drake Lab focuses on identifying kinase activation in pathways that promotes this castration resistant behavior, and subsequently identifying treatments to directly affect the kinases involved.
To identify kinase activation, kinase pathways, and develop predictive biomarkers using in vivo mouse model systems, human cancer model systems, phosphoproteomic technology and mass spectrometry.
The eventual goal is to take a metastatic prostate cancer biopsy and determine the activated kinases in it to provide targeted therapies for real time treatment.
Hypotheses:
Tyrosine kinases are actively involved in the growth of prostate cancer despite the lack of androgen available to it.
Targeting tyrosine kinases to inhibit them will result in the cessation of prostate cancer growth.
A cell line-derived cancer can provide experimental data that will hold true for in vivo human and mouse model systems.
The in vivo mouse model systems are effective and provide results that may be replicated in a patient.
Specific tyrosine kinases can be targeted to prevent further cancer growth, even after the cancer has metastasized, without further ill effects.
Any activated tyrosine kinases in a prostate cancer biopsy can be identified and targeted.