Importance of predictive biomarkers related to Pharmacogenetics in breast cancer and prostate: a systematic review

Pharmacogenetics allows to verify the genetic polymorphisms that influence the success of an oncological pharmacotherapy, therefore, the need for progression in the pharmacogenomic oncological field is evident. This study aims to describe the importance of predictive biomarkers related to pharmacogenetic breast and prostate cancer through a literature review. The search for original articles took place between February and November 2020 in databases such as Pubmed, Scielo, Medline and search directories such as Google Scholar. As for the inclusion criteria, the original articles in English, Portuguese and Spanish published between 2010 and 2020 were included. The search result found 102 articles on the subject, 36 excluded because they were review articles, 22 excluded after reading the abstract and 13 excluded because they did not align with the theme. 31 original articles were selected for which the authors prove the importance of validating independent studies on predictive values of biomarkers for breast and prostate cancer. The conclusion of the analyzed studies suggests that the use of biomarkers makes it possible to predict responses to clinical treatment, appropriate therapeutic conduct where they are associated with better treatment results.


Introduction
According to the National Cancer Institute (INCA), in 2020, 66,280 new cases of breast cancer and 65,840 new cases of prostate cancer are estimated in Brazil. These are the neoplasms with the highest incidence in men and women in the country, therefore, it is extremely important to optimize treatment, rationalizing and individualizing antineoplastic therapy with the aid of PGx tests identifying polymorphism in specific pharmacogenes (INCA, 2021).
Pharmacogenetics (PGx) is a genetic tool that emerged in the 1950s through several observations of inheritable enzyme deficiencies that caused toxicity to certain drugs. It is the science that provides the optimization of therapeutic management in terms of safety and effectiveness, based on the genetic characteristics of patients (Álvarez et al., 2019).
Pharmacogenetic tests allow to verify the genetic polymorphisms that influence the success of a pharmacotherapy.
Through the administration of personalized treatments, we can increase the number of positive responses and reduce the rate of occurrence of adverse reactions and toxicity (Fricke et al., 2018). The preference for the application of PGx tests in the area of oncology is due to its aggressiveness, rapid proliferation of cancer cells and the severity of symptoms. In the clinical context, PGx has shown great importance in the treatment of prostate and breast cancer. Which are the most prevalent cancers among men and women in Brazil (Schilling et al., 2017).
Thus, it is essential to set goals that allow this therapeutic approach to be included as an important portion of pharmacotherapy, being present in hospital and outpatient settings. Increasingly relevant, scientific information is able to allow the personalization of therapy, where PGx, pharmacodynamics and pharmacokinetics, needs to be assimilated and used by pharmacists in order to promote an increase in the patient's quality of life, through greater efficiency and drug safety (Santos, 2017). Therefore, the use of PGx tests allows cancer patients to experience an individualized treatment, with the correct, specific, safe drug, with the most appropriate and consequently more effective dosage and with a lower incidence of adverse effects during chemotherapy. It is also considered, the significant advance in the area of molecular oncology, or oncobiology, taking into account the adoption of PGx and pharmacogenomics, resulting in positive consequences in the enhancement and improvement of pharmacological treatment. The accessibility to these genetic tests is increasing, since the values are increasingly lower, making it possible to use them in clinical practice as a medullary tool in the fight against cancer (Santos et al., 2016).
Thus, the objective of the study was to describe the importance of pharmacogenetic tests in the treatment of breast and prostate cancer in clinical practice, through a systematic review, analyzing the main predictive biomarkers for these neoplasms.

Methodology
It was a study with an investigative approach constituted by a qualitative systematic review, carried out according to the checklist of the PRISMA protocol, with data collection from bibliographic searches in the period between February to November 2020.

Prostate Cancer
The search strategy identified 61 articles. Of this total, 28 were excluded because they were duplicated and / or the study model was based on a literature review, leaving 33 original articles. When reading the abstracts, 6 articles were excluded because they did not address the topic in question, leaving 27 articles read in full. After reading and analyzing the articles in full, 12 were excluded because they did not fit the research theme and finally, 15 were selected ( Figure 1).
The main information about the 15 studies used in our results can be found in Table 1.

Breast Cancer
The search strategy identified 41 articles. Of this total, 8 were excluded because they were duplicated and / or the study model was based on a literature review, leaving 33 original articles. When reading the abstracts, 16 articles were excluded because they did not address the topic in question, leaving 17 articles read in full. After reading and analyzing the articles in full, 1 was excluded for not adapting the research topic. Thus, 16 articles were selected ( Figure 1).
The main information about the 16 studies used in our results can be found in Table 2. ER, PgR, Ki67, p27 (Kip1) and histological grade as predictors of complete pathological response in patients with HER2-positive breast cancer receiving neoadjuvant chemotherapy using taxanes followed by fluorouracil, epirubicin and concomitant cyclophosphamide with trastuzumab Determine whether pCR was related to histological grade (HG) and to several biological factors, including p27 (Kip1). E Also assess the prognosis of the pCR and non-pCR groups, and the expected differences between those positive and negative for lymph node metastases after chemotherapy.

Prostate cancer
The tumor marker most used in the diagnosis and prognosis of prostate cancer is the prostate specific antigen (PSA), however, its contribution is limited because this marker is specific for the prostate and not only for malignancy, therefore, in cases of pathologies such as benign prostatic hyperplasia and prostatitis serum PSA levels may also be elevated (Almeida et al., 2007;Saxby et al., 2020). Therefore, validating new biomarkers that optimize the evaluation of the response to CaP treatment would benefit patients with individualized therapies. In this review we seek to explore relevant studies that focus on promising biomarkers in the clinical management of men diagnosed with PCa.
Patients with castration-resistant prostate cancer (CRPC) are directed to two main antiandrogen drugs (enzalutamide and abiraterone). This medication class meant an advance in the treatment of this neoplasia, in relation to the treatment with androgen deprivation therapy (TPA), improving the quality of life and the overall survival of these men. However, 20-40% of patients treated with these drugs do not benefit from their effects because they acquire primary resistance and almost all have secondary resistance. One study shows the association between resistance to enzalutamide and abiraterone, the detection in CTCs of messenger RNA variant 7 of the androgen receptor splice (AR-V7) and PSA results (Antonarakis et al., 2014). The authors show that 31 patients received treatment with enzalutamide and 31 with abiraterone and PSA measurements were obtained every 1 and 2 months. Thus, 39% and 19% of patients respectively had AR-V7 expressed as CTCs in blood samples, in addition, AR-V7 negative patients had lower PSA response rates and longer PSA progression-free survival and overall survival, the which means that this androgen receptor isoform encoded by the splice variant 7 may represent a predictive biomarker for treatment with antiandrogen drugs, since the expression of AR-V7 in these patients with CRPC does not indicate any form of resistance to taxane chemotherapy . In addition, a study conducted in Canada and the United States has shown that the use of the AR-V7 test can impact decision-making when choosing therapy. Patients with positive AR-V7 were those who had the greatest changes in therapeutic management, which led to clinical improvement due to the use of taxanes (Markowshi et al., 2017).
Another molecular group that is linked to drug resistance in the treatment of CaP are miRNAs. Small RNAs of approximately 22 nucleotides, which at the post-transcriptional level negatively regulate gene expression and when deregulated can serve as oncogenes or tumor suppressing agents. These RNAs can be detected in the serum and serve as predictive biomarkers in resistance to chemotherapy drugs such as docetaxel (Shi et al., 2010). In a study whose objective was to characterize the role of miR-181a in docetaxel-resistant prostate cancer, it measured the expression of miR-181a in C4-2B and

DU145 parental and docetaxel-resistant cells in TaxR (DU). It was concluded that the expression of miR-181a is elevated in
TaxR cells (8.6 times) and DU145-DTXR (7.4 times) compared to parental C4-2B and DU145 cells, respectively.
Overexpression of miRNA-181a significantly improved cell survival in the presence of docetaxel (ie, resisted this treatment) compared to the miR mimicking control in parental C4-2B cells. However, docetaxel-resistant TaxR cells were resensitized by miR-181 to that same drug. The same study also demonstrated cross-resistance to cabazitaxel and resensitization of miR-181a TaxRcomknockdown cells. Thus, these findings are significantly relevant and may contribute to a more appropriate choice of therapy for the patient that presents data that prove resistance to docetaxel (Armstrong et al., 2017).
Another promising proposal for the treatment of patients with CaP is the neuroendocrine biomarkers. Neuroendocrine differentiation (NED) is equivalent to the association of unfavorable prognosis and serum levels of chromogranin A (CgA) and neuron specific enolase (NSE), neuropeptides stored in neuroendocrine cells (Genitsch et al., 2017). Study aimed to assess the value of the markers (NED) to help select the best treatment sequence for abiraterone acetate (AA) and docetaxel-prednisone (DP) in men with mCRPC, showed through blood samples from 88 patients, the levels ofCgA and NSE measured before first line treatment. Patients with a high level of baseline NED markers proved to be more beneficial in receiving a sequence of DP-AA treatment instead of AA-DP. This group of men had an overall median survival of 21.7 months with DP-AA treatment and 19.9 months with AA-DP treatment, respectively. In addition, the same study found that a patient with mCRPC with elevated serum NED levels, has a response to chemotherapy with PD, decreased levels of NED. According to the authors, this fact is related to patients with high baseline NED levels that respond better to the DP-AA sequence instead of the AA-DP (Fan et al., 2019).
Almost 100% of patients with mCRPC have bone metastasis. These terminally ill men suffer from severe progressive pain, among other consequences of this distension. Bone metabolism occurs through the synthesis of new bone mediated by osteoblasts and bone resorption mediated by osteoclasts. This process is regulated by the balance between the two phenomena, however, in patients with mCRPC this homeostasis is not regulated and ends up being compromised by emphasizing the activity of osteoblasts and, therefore, favoring bone formation (Lara et al., 2014). A prospective multicenter study with the objective of evaluating the predictive capacity of serum bone markers in patients with mCRPC and the risk of mortality was developed between 2002 and 2005 with 52 patients. In the result, it was observed that 34 patients died and 18 were alive at the time of the last evaluation, where the concentrations of bone markers, mainly ICTP and PINP, were higher in the group of deceased compared to survivors (p <0.05) and that the combination of these markers is able to predict mortality in the next 24 months in the analysis performed where AUC values> 0.7 were presented, with sensitivities / specificities between 70% and 80%. Therefore, patients with advanced mCRPC can especially benefit from ICTP and PINP markers as predictors of survival both to be aware of their health status and for the physician to rethink the best additional therapeutic management (Jung et al., 2011).

Breast cancer
Breast cancer is a prevalent malignancy in the female population, as it is a complex disease, several factors interfere with the prognosis and the outcome of a specific therapeutic regimen. Each type of breast cancer has a different behavior, precisely because these neoplastic cells express hormone receptors (estrogen and / or progesterone) and HER2 protein, causing the cancer to vary its way of tumor progression (Manica et al., 2017). The present study was therefore conducted by analyzing the status of different predictive factors in breast carcinoma subtypes, elucidating the correlations of these factors, in order to identify significant relationships between the types of breast cancer. It is necessary to identify predictive biomarkers that assist in individualized therapy in view of the heterogeneities of breast neoplasms.
Studies have observed the relationship of dasurvivin, a member of the apoptosis protein inhibitor family, as an attractive target for treatment against various carcinogens. Survivin expression is constantly related to poor prognosis in a wide variety of cancer patients. To express the expression of survivin, ASOs (survivin oligonucleotide) were employed, which negatively regulates the expression of survivin in human cancer cells, in an attempt to create another therapeutic drug, showing that the function or inhibition of survivin by the oligonucleotide LY2181308 boosted apoptosis in cancer cells and inhibiting the growth of xenograft tumors in nude mice. Furthermore, LY2181308 has been shown to sensitize tumors to chemotherapeutic agents such as gemcitabine, paclitaxel and docetaxel. Due to its differential expression in normal tissues and its function in apoptosis, survivin is a promising target for cancer therapy (Carrasco et al., 2011).
Another promising study is miRNAs, which act as oncogenes and tumor suppressors in the development and metastasis of breast cancer. It is possible that the various roles that miRNAs play have the potential to provide valuable information in a clinical setting, demonstrating the potential to act as both screening tools for stratifying high-risk patients, while informing the decision-making process of treatment (Asia et al., 2018). The miR-143 marker was investigated through data from studies with patients with locally advanced triple negative breast cancer, discriminating the complete pathological response and the polymerase-free chain reaction, receiving neoadjuvant treatment based on fluorouracil-cisplatin / paclitaxel. MiR-143 has been shown to be a potential predictor of response to neoadjuvant therapy in triple negative breast cancer (García-Vázquez et al., 2019).
In another analysis, it highlights the tumor's circulating DNA (ctDNA), which is found in the bloodstream and refers to the DNA that comes from cancer cells and tumors. CtDNA are small pieces of DNA, usually comprising less than 200 nucleotide blocks in length. The study carried out by means of high-level sequencing of a personalized panel in blood samples, three somatically mutated genes were detected, PIK3CA, TP53 and KMT2C. This study was the first to explore the link between prognosis and ctDNA after neoadjuvant therapy in Chinese breast cancer patients. The incidence of KMT2C mutations was high in patients with breast cancer, especially among patients with triple-negative breast cancer (TNBC).
Kaplan-Meier survival and multivariate analyzes show that KMT2C ctDNA could be a predictor of breast cancer recurrence, while the association between KMT2C and efficiency of neoadjuvant therapy was negligible. The study highlights the ability of ctDNA analysis at different times to assess tumor progression and treatment effectiveness, such as predicting breast cancer recurrence (Hao et al., 2020).
The increasing use of the monoclonal antibody trastuzumaboth against the extracellular site of the human epidermal growth factor receptor type 2 (HER2). Its use caused a decrease in the progression of breast cancer in patients who underwent chemotherapy treatment alone or in combination with trastuzumab. Therapy involving anti-HER-2 is an ideal modality, and blocking HER-2 by means of trastuzumab is effective in cases of initial or metastatic breast cancer (Haddad, 2010).
As verified in a study of TRPM2 expression (potential cationic channel of transient receptor), it was observed that the low expression of TRPM2 is used to predict bad results and a greater possibility of recurrence in relation to ER-and HER2 + breast carcinoma. Therefore, TRPM2 is a biomarker for new therapies (Sumoza-Toledo et al., 2016).
Attested by means of a study, in which 678 cases of breast cancer tissue were selected by means of immunohistochemical staining of hormone receptors and growth of human hypodermic, that the increase of the nuclear expression of YAP (regulatory protein of the transcription of genes of cell proliferation and suppression of apoptotic genes) is related to decreased overall survival rate in breast cancer and overexpression of cytoplasmic YAP in HER-2 type breast cancer in which it was associated with shorter disease-free survival rate . That through this, there is an important difference in the expression of YAP and pYAP according to the molecular subtypes and tumor components. Nuclear and cytoplasmic expression of YAP appears to be a prognostic marker for patients with breast cancer (Kim et al., 2014).
It was also shown that hormone receptor (HR) negativity and the high Ki67 protein index are two independent factors to predict a higher complete pathological response (pCR) in breast cancer positive for axillary / HER2-positive lymph nodes. In particular in patients with HR-negative / high Ki67 index, the pCR rate reached 70.0%, suggesting that this patient population may obtain more benefits from neoadjuvant therapy containing paclitaxel, carboplatin and trastuzumab (Ding et al., 2017). We attest to the similarity of pCR biomarkers with the Ki67 marker, associated with cell proliferation and labeling index (LI) at baseline may be predictive of survival rates in patients with breast cancer with HER2 overexpression similar to luminal (Kurozumi, et al., 2015).
It was examined that the absence or low expression of the ADAM33 protein contributes to the increased aggressiveness and metastases of breast cancer. The present study has shown, in an unprecedented way, that ADAM33, in combination with currently available biomarkers, can be a new molecular marker to better determine the prognosis of breast cancer. The importance of ADAM33 in TNBC-negative triple carcinoma and basal-type carcinoma (BLBC) is clear and may improve our knowledge of the most aggressive breast cancer subtypes. In addition, LumA and LumB breast carcinomas showed a strong signal for ADAM33. Conferring that the absence of eobitus metastases was related to the high expression of ADAM33. These results suggest that ADAM33 may be a significant marker of good disease prognosis because breast carcinomas LumA and LumB are less aggressive compared to tumor subclasses HER2 +, TNBC and BLBC (Manica et al., 2017).
The chemokine receptor (CXCR4) is a receptor coupled to transmembrane G protein seven and stimulating tumor growth, angiogenesis and metastasis in various types of cancer. It is a class of biomarker with predictive potential associated with promoting resistance to tamoxifen via the AKT (Protein kinase B) pathway. In addition, the AMD3100 CXCR4 antagonist reversed tamoxifen resistance in breast cancer by inhibiting AKT phosphorylation. As mentioned, the combination of endocrine therapy and other component inhibitors that mediate endocrine resistance is one of the suggested methods for breast cancer resistant to endocrine therapy. The combination of tamoxifen and AMD3100, a specific CXCR4 antagonist, can increase the tumor suppressor effects and reduce the potential side effects arising from the dosage of the drug .

Conclusion
The results of this study demonstrate the biomarkers with substantial potential in the treatment of breast and prostate cancer. The management in which the results were presented, consider the use and assistance of biomarkers for chemotherapy / radiotherapy, in which they provide the prediction of responses to clinical treatment, and they are associated with better results.
The clinical application of these predictive biomarkers can enable numerous advantages, among them, better adherence to treatment because it becomes a therapy based on the genetic individuality of a given patient. Consequently, with a more specific therapy, less toxicity and possible side effects are observed, which reduces expenses with medications and additional hospitalizations.
However, there are no universally accepted predictive markers of response to cancer treatment, and the few that have been investigated in the neoadjuvant context are most often predetermined markers are present. The accession of new biomarkers can expand the therapeutic regimen options currently available to doctors. Therefore, it is necessary to expand experiences to characterize the real value of using each biomarker in cancer therapy, since, currently, studies demonstrate positive results with safe, efficient and cost effective therapies with the help of pharmacogenetics.