Prostate cancer (PCa) is a global issue with increasing rise in morbidity and mortality. PCa treatment has been a global challenge for many years because drugs designed to combat this disease might show low efficacy as a result of low solubility. Limitations of chemo-drugs for treating PCa give birth to the use of nanomedicine which helps to improve drug delivery systems. Nanoemulsions are particles that are pharmaceutically formulated and comprised within the range of a nanometer (10-200nm). Nanoemulsions are thermodynamically stable and made up of safe gradient agents. This chapter elucidates the physiological, biological, and molecular barriers affecting drug delivery in PCa. The authors discussed the importance of nanoemulsions as potential drug delivery mechanisms in PCa therapy. This chapter focuses on reviewing different ways by which nanoemulsion can bring solution to water-solubility problems and also target specific cancer cells. Limitations of nanoemulsions in the drug delivery field were also highlighted.
TopIntroduction
Prostate is an accessory gland associated with the male sexual system in mammals (Roehrborn, 2006; Luke and Coffey, 1994). The prostate helps in the production of fluid that helps in sperm functioning (Luke and Coffey, 1994). In humans, it surrounds men urethra; it is differentiated into different glandular regions such as the peripheral zone and the transition zone. Peripheral zone encircles the proximal prostate urethra where 70-85% of adenocarcinoma occurs (Noguchi et al., 2000) while the transition zone surrounds the distal prostate urethra and benign hyperplasia lesions occurs in this area. In a normal condition, the prostate grows and mature during puberty as the androgen levels increases. Its growth is primarily regulated by testosterone (Prins and Lindgren, 2014).
Globally, Prostate cancer (PCa) is the most common non-cutaneous cancer with an estimation of one million, six hundred thousand cases and three hundred and sixty-six thousand deaths in a year (Torre et al., 2015). PCa is characterized by aberrant dividing cells in the prostate gland which leads to abnormal growth of the prostate gland. Prostate malignant transformation follows a multiple process, starting from prostatic intraepithelial neoplasia (PIN) to localized prostate cancer and followed by the advanced prostate adenocarcinoma in which with the primary invasion leads to metastatic prostate cancer. Following histological patterns of prostate cancer, the Gleason grading system (Gleason and Mellinger, 1974) has been used to identify prostate cancer stages and it has been refined over the years (Epstein et al., 2014; 2016). Death from PCa normally occurs as a result of metastasis when the cancer cells spread to other part of the body. Regions in which the cancer cell can spread include the pelvic, lymph nodes, bladder, rectum, brain and bone.
Presently, there are no preventive measures for prostate cancer, however, nutrition and lifestyle changes have been suggested as ways of prevention but research studies are still ongoing and scientific recommendations are not available at the moment. Pomegranate, green tea, broccoli, crocetin, flaxseed, soy extracts, vegan diets and physical exercise have been proposed to lower the risk of PCa development. Majority of the studies associated with prevention and inhibition of PCa have been done in animal models but it is challenging how these results can be interpreted and applied in human PCa (Schatten, 2018).
Hormone responsiveness is an important characteristic of prostate cancer (Huggins and Hodges, 1941). Huggins and Hodges reported that castration led to decrease in tumor in patient with prostate cancer (Huggins and Hodges, 1941). Androgen deprivation therapy (ADT) which involves the use of agents that obstruct the androgen pathway is used in the treatment of prostate cancer. However, there can be resistant to ADT which can result in primary castration-resistant prostate cancer (CRPC) or the metastatic type (mCRPC) (Zou et al., 2017). The use of drugs (Pharmacotherapy) in PCa depends on the stage of the disease. In one perspective, early detection and use of drugs is encouraged (Armstrong and Gao, 2015; Malarvizhi et al., 2014). In another perspective, drugs are used after surgical removal and radiation (Maeda, 2012). The use of drugs in treating prostate cancer is challenging as a result of little vascularization as the disease progresses (Maeda, 2012). Some of the chemo drugs (chemotherapy) for treating prostate cancer include docetaxel (taxotere), cabazitaxel (jevtana), mitoxantrone (novantrone) and estramustine (emcyt). These drugs are associated with limited efficacy and the associated risk or side effects on patients outweigh the efficacy (Armstrong and Gao, 2015). Armstrong and Gao (2015) reported the association between the metabolism of cancer tissue and drug resistance, this causes a challenge in the effectiveness in the use of drugs. In order to solve the problem of drug resistance, there is need to subsequently increase the dose of the drug which in turn leads to systemic accumulation of the drug and toxicity Therefore, there is an urgent need to improve drug therapy and drug delivery system by increasing specificity with less systemic toxicity.