Autophagy inhibition and DNA repair in prostate cancer cells

Prostate cancer is a type of cancer that develops in the male reproductive system, and most prostate cancer can be slow growing. However, there are still aggressive type of prostate cancers, because the cancer cells can spread from the prostate of a patient to all other part of the body particularly the lymph nodes and bones. Initially, prostate cancer may reveal no symptom, however, in a later stage, it can cause pain, erectile dysfunction, urinating difficulty, problems in having sexual intercourse and sometimes death. Prostate cancer is common among the older men especially men reaching age of 50 and above, however, the rate of prostate cancer varies across the world. Its widespread is more frequently in Europe and the United States than in the South and East Asia. Globally, "prostate cancer is the 6th leading cause of cancer-related death in men." (Siegel, 2011, p 212). However, the prostate cancer is more common in the advanced countries than underdeveloped world. It is now the first cause of death among men in the UK and second in the United States. However, factors such as diet and genetics have been identified as the causes of prostate cancer; however, light pollution has also been identified as the cause of prostate cancer. One of the methods to establish a prostate cancer cell line is LNCaP, which is established from a human lymph node. (Schwickart Huan. Lill, et al.(2010). The study establishes research aims to enhance a greater understanding of prostate cancer.

Research Aims

1-To understand the mechanism how autophagy inhibition targets directly the ubiquitination of γH2AX.

2-Test whether shATG7 knockdown induced LNCap cells could influence γH2AX level following radio sensitivity by suppressing DNA repair.

3-To determine the interacting partner of USP14 in autophagy deficient cells.

The study reviews the related study to enhance a greater understanding of the research aims.

Review of Related Studies

"Autophagy is a self degradation process that can mediate cell death as well as survival. Autophagy induced during starvation, growth factor deprivation, hypoxia, endoplasmic reticulum (ER) stress, and microbial infection can prevent cell death" (Singh, Sharma, Mir, et al. 2014, p 13).

Kroemer, Marino, Levine, (2009) also point out that autophagy is evolved from unicellular that is capable of surviving on nutrient stress. Moreover, autophagy involves lysosomal degradation of cytosolic components. However, autophagy can be integrated in other cellular through mutual control. Autophagy can also be associated to cell death with excessive mitophagy, which lead to a loss to caspase activation as well as lysosomal membrane permeabilization.

Lock, Roy, Kenific (2010) argue that the protumorigenic functions and autophagy are attributed to the increase of cancer cell. The authors demonstrate that there is an unexpected connection between glucose and autophagy, which facilitates transformation of adhesion-independent driven by a strong oncogenic. The authors also test the effect ATG knockdown. The shATG7-2 was suspended with the absence of pepstatin A (E/P) and E64d. The results reveal the mean of ± SEM, which reveals three or more independent experiments.

Singh, (2011) point out that survival signaling and cell death are critical for the cellular response against ionizing chemotherapy and radiation in PCa (prostate cancer). Typically, Apo2L/TRAIL, and IR are widely used for the therapeutics for prostate cancer, however, resistance cellular that have been developed over time may hinder the effectiveness of therapeutics. Singh (2011) demonstrates an investigation on a response of IR (ionizing radiation) and Apo2L/TRAIL in PCa cell lines. Essentially, PC3 cells are more to cell-mediated death of Apo2L/TRAIL compared to LNCaP-derived C4-2.

However, Subramaniam et al. (2013) argue that USP14, deubiquitinating enzyme in association with the proteasome is critical to mediate ubiquitin trimming as well as ensuring ubiquitin trimming. However, ageing is associated with decline in proteasomal proteolysis, and the USP14 has a contributory role in the decline proteasomal proteolysis. The authors argue that proteasome-associated USP14 in association with the enzymatic activity is significant higher in T cell of people aged 50 and above. Thus, increase in USP14 could enhance chemically inhibiting proteasome. The authors also investigate whether the USP14 activity could regulate proteasomal proteolysis. Typically, T cells of young people shows increase degradation of I-B?, however, the T cells of elderly people are unaffected by IU1 pretreatment. The results reveal that a decrease of proteolysis of proteasomal substrates among elderly people could make elderly people to be suspectible to prostate cancer.

Essentially, the prostate cancer is common among elderly people because Proteasome associated with enzyme USP14 increase significantly with increase in age. With increase in overall cellular levels of USP14, increase in USP14 activity in the T-cells of aged people is attributed to low level of proteasomal proteolytic activity. However, Todi, & Das (2012) point out that increasingly large family of the deubiquitinases and enzymes play a critical role in health and disease, Typically, Ubiquitin is pathway to many disease, and a growing number of deubiquitinases have been linked to cancer either as tumor or oncogenes suppressor. Thus, it is very evident to focus on the deubiquitinases therapy. The proteasome-associated DUB is a specific inhibitors specific to USP14. Typically, "USP14 was also shown to rescue proteins targeted for degradation by deubiquitinating them at the proteasome. Consequently, cells that do not express USP14 show enhanced clearance of several disease-related proteins, including one that can cause familial Alzheimer's disease." (Todi, & Das, 2012, P 1). Sippl, et al. (2014) argues that USP14 is proteasome destined to proteasomal degradation.

Yang.Chee, Huang. et al. (2011) in their own case argue that autophagy delivers dual roles in cancer: "acting as both a tumor suppressor by preventing the accumulation of damaged proteins and organelles and as a mechanism of cell survival that can promote the growth of established tumors." (p 1533). Essentially, autophagy inhibitors can enhance death of tumor cell induced by anticancer drug. Inhibition of autophagy is sensitizing to cells resistance. Moreover, autophagy inhibitor enhance antibody against EGFR. The autophagy also reduces tumor burden in a colon cancer.

Moreover, the autophagy also plays a critical role for cancer prevention and tumor suppression, which is strategy for cancer prevention. Typically, autophagy assists cells to survive using energy production that will lead to tumor growth as well as therapeutic resistance. Essentially, autophagy is the evolutionary and homeostatic assistance in degrading cellular protein and organelles, which maintaining cellular biosynthesis during metabolic stress. Moreover, autophagy is very important in all cells, which assists in removal of damaged long-lived organelles and protein. Thus, autophagy could play a critical role in preventing tumor and a mechanism for tumor suppression.

Li, et al. (2014) argue that DDR (DNA) damaged response plays a critical role in regulation and repair of protein. Essentially, a deubiquitinating enzyme is critical in eliminating of ubiquitin signal. The depletion of sensitive cells can cause disappearance of γH2AX foci following the Bleocin treatment. More importantly, DNA damage if not repair can lead to cell death as well as chromosomal instability that could eventually lead to a premature aging. Sippl, Collura, Colland, (2011) in their own case point out that Ubiquitin-specific proteases are associated to deubiquitinating enzymes used to remove ubiquitin protein substrates. Essentially, DNA alteration in different types of cancer as well as prostate cancer makes the ubiquitin to be attractive for cancer recovery.

Method

The study will use experimental method to achieve the following research aims:

To understand the mechanism how autophagy inhibition targets directly the ubiquitination of γH2AX.

Test whether shATG7 knockdown induced LNCap cells could influence γH2AX level following radio sensitivity by suppressing DNA repair.

To determine the interacting partner of USP14 in autophagy deficient cells.

In carrying out the experimental method, the researcher will use objective observation strategy that will be verified by other scientists. The study will make an objective statement, which include:

Autophagy inhibition targets directly the ubiquitination of γH2AX.

shATG7 knockdown induced LNCap cells and influence γH2AX level following radio sensitivity by suppressing DNA repair.

Interacting partner of USP14 in autophagy deficient cells.

These observations will be based on scientific method to make objective observations. The research will be based on the specific scientific events already happened and will be verified through scientific method.

Hypothesis

The study will also use the hypothesis to achieve the research aims. Major reasons for using hypothesis are to make tentative predictions for the experiment. The hypotheses will consist of research and null hypotheses presented as follows:

H1: Mechanism of autophagy inhibition targets directly the ubiquitination of γH2AX is to carry out the autophagic analysis using genetic and pharmacological TEM (transmission electron microscopy) and chloroquine approaches.

H0: Mechanism of autophagy inhibition targets directly the ubiquitination of γH2AX is not to carry out the autophagic analysis using genetic and pharmacological TEM (transmission electron microscopy) and chloroquine approaches.

H1: Testing of shATG7 knockdown induced LNCap cells could influence γH2AX level following radio sensitivity by suppressing DNA repair.

H0: Testing of shATG7 knockdown cannot induce LNCap cells could influence γH2AX level following radio sensitivity by suppressing DNA repair.

H1: Interacting partner of USP14 in autophagy deficient cells could lead to prostate cancer recovery

H0: Interacting partner of USP14 in autophagy deficient cells could not lead to prostate cancer recovery.

Moreover, the study will use genetic and pharmacology approach to carry out the experiment. Typically, the autophagy pharmacological inhibition is to use TR induced cell death to detect its effect on PC3 cells. To detect the presence of autophagic, it is critical to use TEM (transmission electron microscopy) which is the widely used technique to monitor the presence of autophagy. The genetic inhibition will involve reducing the shATG7 while increasing shLAMP2-expressing cells. The extent of knockdown will be estimated to be > 50% for ATG7 in C4-2 cells and PC3 cells.

The proposal will use the following materials to carry out the experiment:

Ethical Considerations

The researcher will secure approval from appropriate authorities before carrying the research. The study will also protect all the information of all the human subjects that will be used for the experiment to achieve 100% privacy.

Conclusion

The paper carries out the research proposal on prostate cancer. In both developed and developing countries, prostate cancer is one of the leading causes of death among older men aged 50-year and above. The study reviews previous studies to enhance a greater understanding on the prostate cancer. Moreover, the study will use experimental research to complete the proposal, and the quantitative statistical technique will be used to carry out data analysis using correlation techniques. The research method and data analysis will assist in achieving the following research aims:

1-To understand the mechanism how autophagy inhibition targets directly the ubiquitination of γH2AX.

2-Test whether shATG7 knockdown induced LNCap cells could influence γH2AX level following radio sensitivity by suppressing DNA repair.

3-To determine the interacting partner of USP14 in autophagy deficient cells.

This study will provide several contributions:

First, the study will assist in understanding mechanism of prostate cancer, which will assist in arriving at the solution for the management of prostate cancer.

Moreover, the research outcome will assist in understanding interaction of USP14 in the autophagy deficient cells.

More importantly, the study will assist in understanding the shATG7 knockdown and its influence on γH2AX level following radio sensitivity by suppressing DNA repair.

The study will contribute to the body of knowledge of academic and medical communities.

Reference

Kroemer, G.L, Marino G, Levine, B. (2009). Autophagy and the integrated stress response. Cell Death Differ. 16(1):21-30.

Li, N.S.L. Hsieh, W.L. Rapic-Otrin, C. et al. (2014). Ubiquitin-Specific Protease 5 Is Required for the Efficient Repair of DNA Double-Strand Breaks: e84899. PLoS One. 14;9(1).

Lock., R. Roy., S. Kenific., C.M. (2010). Autophagy facilitates glycolysis during Ras-mediated oncogenic transformation. Mol. Biol. Cell. 22(2): 165-178.

Siegel., R, (2011). Cancer statistics, 2011: the impact of eliminating socioeconomic and racial disparities on premature cancer deaths. CA Cancer J. Clin, 61 (4): 212 -- 236.

Sippl, W. Collura, V. Colland, F.(2011). Ubiquitin-specific proteases as cancer drug targets. Health and Wellness Resources Center.

Singh, K. (2011). Molecular Basis of Autophagy-Mediated Resistance to Radiation and Apo2L/TRAIL Therapy in Prostate Cancer Cells. U.S. Army Medical Research and Materiel Command, Maryland.

Singh, K. Sharma, S. Mir, M.C. et al. (2014). Autophagic flux determines cell death and survival in response to Apo2L/TRAIL (dulanermin). Mol Cancer: 13: 70.

Subramaniam, P. Michela, P. Dennis, S.H. et al. (2013). Compensatory increase in USP14 activity accompanies impaired proteasomal proteolysis during aging. Pub Med Central.

Schwickart M. Huang X. Lill, J.R. et al.(2010) Deubiquitinase USP9X stabilizes MCL1 and promotes tumour cell survival. Nature, 463:103-107.

Yang, Z.J.Chee, C.E. Huang, S. et al. (2011). The Role of Autophagy in Cancer: Therapeutic Implications. Mol Cancer Ther; 10:1533-1541.