Genetic Controls of Androgen and its Effect on Prostate Cancer Drew Mendoza 1
Genetic Controls of Androgen and its Effect on Prostate Cancer
This year in the United States, there will be 186,320 new cases of prostate cancer and 28,660 deaths due to prostate cancer (National Cancer Institution). It is the second leading cause of death in North American men (Higuchi et al.
, 2006).
One of the main treatments for prostate cancer is ablation, or removal of androgens. Androgens are all the male sex hormones, testosterone being the most famous of these. Initially, prostate cancer begins as androgen-dependent, but as it progresses, the cancer becomes androgen-independent. When androgen ablation therapy is conducted, it forces the cancer cells into apoptosis, or programmed cell death. However, an unknown mechanism allows the cells to develop androgenindependence, thus allowing continued multiplication. Once the cancer has progressed to androgen-independence, androgen-ablation becomes an ineffective treatment
(Higuchi et al.
, 2006).
Three recent experiments have been conducted that examine the link between androgen dependency and prostate cancer. These tests deal with the mechanism that allows cancer prostate cells to avoid apoptosis, mitochondrial DNA control of androgen dependency, and the effect of transcription factor and microRNA regulation on androgen.
Recently, Lorenzo and Saatcioglu focused on the crosstalk, or interference, between the androgen receptor (AR) pathway and the c-Jun N-terminal kinase (JNK) pathway. In the AR pathway, the androgen receptor regulates the transcription of particular genes. The JNK pathway is a signal transduction pathway that

Genetic Controls of Androgen and its Effect on Prostate Cancer Drew Mendoza 2
“ phosphorylates and activates...a number of transcription factors such as c-
Jun”
(Lorenzo and Saatcioglu, 2008). The trigger of JNK had been shown to occur with apoptosis, or programmed cell death. Therefore, Lorenzo and Saatcioglu show how interference in the JNK pathway by the androgen of the AR pathway prevents JNK activation and thus, apoptosis (Lorenzo and Saatcioglu, 2008).
In the experiment, LNCaP cancer cells were treated with R1881, a potent androgen, and then with 2 apoptosis-inducing agents, thapsigarin (TG) and phorbol ester 12-O-tetradecanoyl-13-phorbolacetate (TPA). “As shown in...[figure 1], R1881 treatment decreased LNCaP cell death induced by both TG and TPA by approximately
50%” (Lorenzo, 2008). To measure the JNK activation affected by androgens, an
Figure 1: Apoptosis in LNCaP cells treated with R1881 and the apoptosis inducing agents TG and TPA
Figure 2 : R1881’s affect on JNK activation at different time intervals in TG and TPA treated LNCaP antibody was used to identify the exact form of JNK at the times of apoptosis due to TG and TPA. The results, figure 2a-b, showed an almost complete deletion of JNK activity at 6 hours and partial deletion at later hours in the R1881 treated LNCaP. Lorenzo’s experiment allows for better understanding of androgen’s effect on apoptosis,

Genetic Controls of Androgen and its Effect on Prostate Cancer Drew Mendoza 3 specifically in the JNK pathway; thus, this research could help find how prostate cancer is able to prevent apoptosis even with a deprivation of androgen (2008).
Higuchi et al. focused on the genetic controls of androgen. They discovered that mitochondrial DNA (mtDNA) is important in the progression of prostate cancer, specifically the loss of androgen dependency. By observing the changes in mtDNA during the progression of the cancer in castrated mice, they determined that a loss of mtDNA leads to androgen-independent cells. Higuchi used LNCaP cancer cells that are androgen dependent to create androgen-independent cells while retaining androgen receptors; these new androgen-independent cells are C4-2 cells. After extracting and amplifying the mtDNA from both LNCaP and C4-2, a southern blot analysis was performed to find the actual levels of mtDNA (Higuchi et al., 2006).
They found that LNCaP cells had 8 times more mtDNA than C4-2 cells. Also, the
LNCaP cells had 4-fold higher in oxygen consumption levels than C4-2 cells (see Fig.
3). These results suggest a direct correlation between the amount of mtDNA in the cell, and its dependency on androgen. Likewise, there is a link between the amount of oxygen consumed by the mitochondria of the cancer cell and its androgen dependency.
These results could help lead to an understanding of the mechanism that controls the loss of mtDNA in prostate cancer and its effect on androgen dependency (Higuchi et al.,
2006).
Wang et al. (2008) also examined the relationship between the progression of prostate cancer and androgen dependency of the cells, but they focused on the affects of transcription factors and microRNA. Transcription factors are proteins that control the transcription of DNA by binding to the DNA. Likewise, microRNAs “bind to the 3'-

Genetic Controls of Androgen and its Effect on Prostate Cancer Drew Mendoza 4 untranslated region (3'-UTR) of target transcripts to regulate gene expression by either inhibiting translation or promoting mRNA degradation” (Wang et al., 2008). In his experiment, Wang et al. (2008) used microarray data to observe the differences in total gene expression of both androgen-dependent and androgen-independent prostate cancer tissues. Using a matrix, the transcription factor binding sites and microRNAs were scored (their GEC). The GEC score are based on several factors that shows how much affect the transcription factor binding site or microRNA had on the difference in the gene expression between androgen-dependent and androgen-independent cells
(the higher the GEC, the higher the affect). Figures 4 and 5 show the 7 transcription factor binding sites and microRNAs with the highest GEC scores (2008). By understanding the transcription factor binding sites and microRNA that create differences, the mechanism that allows cells to change from androgen-dependent to androgen-independent may be found. Their results suggest that in androgenindependent cancer cells, the transcription factors and microRNAs are unable to work as well, as opposed to in androgen-dependent cells. Likewise, their experiment has established a model to be used for further transcription factor binding sites and microRNAs to be assessed according to their different affects on gene expression in prostate cancer (Wang et al.
2008).
All three of the papers discussed above described experiments that are vital to advances in a better treatment for prostate cancer. By having a better understanding of the effects of androgen on apoptosis and the effects of mtDNA, transcription factor binding sites, and microRNAs on androgen dependency, a better treatment for prostate cancer may be found. As of now, there is no effective treatment once cancer cells

Genetic Controls of Androgen and its Effect on Prostate Cancer Drew Mendoza 5 become androgen-independent. However, with this research and continued research to come, the mechanism that allows androgen independency may be discovered, and a treatment to prevent it may be developed.
References
Higuchi, M., Kudo, T., Suzuki S., Evans T. T., Sasaki R., Wada Y., Shirakawa T.,
Sawyer J. R., and Gotoh A. "Mitochondrial DNA determines androgen dependence in prostate cancer cell lines." Oncogene 25 (2006): 1437-445.
Lorenzo, Petra I., and Fahri Saatcioglu. "Inhibition of Apoptosis in Prostate Cancer Cells by Androgens Is Mediated through Downregulation of c-Jun N-terminal Kinase
Activation." Neoplasia 10 (2008): 418-28.
Wang, G., Wang, Y., Feng, W., Wang, X., Yang, J. Y, Zhao, Y., Wang, Y., and Liu, Y.
"Transcription factor and microRNA regulation in androgen dependent and -independent prostate cancer cells." BMC Genomics 9 (2008): 1471-2164.

Genetic Controls of Androgen and its Effect on Prostate Cancer
Figure 3:
“
The effect of androgen ablation on mtDNA and mitochondrial respiratory function.
...
( b ) Indicated amounts of DNA from
LNCaP and C4-2 were subjected to PCR and
PCR bands (16 kb) were shown as described in Materials and methods. ( c ) Total DNA (10
µg) from LNCaP, C4-2 and LN"0-8 was subjected to Southern blotting as described in
Materials and methods.
( d ) mtDNA from 3×10
6 cells from C4-2 was subjected to Southern blotting as described in Materials and methods.
( e ) Oxygen consumption in permeabilized
LNCaP and C4-2 was detected using succinate as a substrate as described in
Materials and methods.
”
(Higuchi 2006)
Drew Mendoza 6

Genetic Controls of Androgen and its Effect on Prostate Cancer Drew Mendoza 7
Figure 4 : “GEC scores...of top 7 selected position weight matrices” (Wang, 2008). Position weight matrices (PWMs) represent transcription factor binding sites.
Figure 5:
“ GEC scores...of top 7 selected microRNAs” (Wang, 2008).