**9. Conclusion**

*Antioxidants*

ment [45]**.**

apoptosis regulator) [14].

result in cell death [42]. In addition to Nrf2, the transcription factor p53 has also been shown to suppress ROS accumulation via directly regulating the expression of a variety of antioxidant genes including SOD2, GPX1, and CAT [14, 39] and through the induction of the metabolic TIGAR gene (TP53-inducible glycolysis and

fruits in general protect against a number of cancers [43].

**7. Advantages of using antioxidants as an anticancer approach**

Oxidative stress can happen due to reduction in enzymatic antioxidant activities. Moreover, it can occur due to ionizing, radiation, chemotherapy, aging, shear stress, cytokines, and growth factor receptor interactions [14]. Antioxidants and oxidative stress interact with the initiation, promotion, and progression of cancer [41]. Actually, the cell-damaging effects of free radicals can be balanced by antioxidants. Furthermore, as the fruits and vegetables are good sources of antioxidants, people who eat them more than others have a lower risk for various diseases such as heart and neurological diseases, and there is evidence that some types of vegetables and

In addition to the standard anticancer treatment options such as chemotherapy, radiotherapy, and surgery, several natural products due to their antioxidant activities have been identified to have a potential for cancer prevention [44] and treat-

In radiotherapy and chemotherapy, ROS and free radicals partly cause various adverse effects [46]. ROS generation causes various tissue or organ injuries; for example, doxorubicin and other anthracycline antibiotics are known to lead to cardiotoxicity [47]; cisplatin and other platinums lead to nephrotoxicity, ototoxicity, and peripheral neuropathy [48]; bleomycin leads to lung injury [49]; and alkylating agents cause DNA damage of drug-treated cells [50]. Tissue or organ injuries may also induce carcinogenesis [51]. Many previous studies reported that using antioxidants with these gold standard methods can significantly decrease these cellular damages. For instance, in one study that is reported by Askua et al., among the 49 studies, 46 examined the reduction of adverse effects by antioxidant supplementation; in 34 trials, possible reductions in chemotoxicities or radiotoxicities using antioxidant supplementation were reported; and only 1 RCT, using vitamin A, reported that supplementation possibly increased chemoinduced toxicities. The remaining 11 studies reported no significantly difference in toxicities between control and supplementation groups [51]. Further, the results of the Shanghai Breast Cancer Survival Study showed that consumption of multivitamins or vitamins such as C and E within 6 months of breast cancer diagnosis correlated with 18% decreased mortality and 22% decreased recurrence rate [52]. In addition, the Life After Cancer Epidemiology (LACE) cohort study results on effects of vitamins E and C and combination of carotenoid supplementation in breast cancer showed that vitamins E and C intake before and after breast cancer diagnosis was related to 22% reduced risk of all-cause mortality, 32% decreased breast cancer mortality, and

We are approaching a new era wherein ROS biology and their effects in the physiopathology of cancer may be dissected with unprecedented detail, bringing potential therapeutic benefits derived from selective manipulations of cancer redox balance to be uncovered, paving the way to novel and exciting investigations in the

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20% decreased recurrence risk [53].

**8. Future therapeutic perspectives**

ROS/RNS protection in cancer is an important issue that attracts many scientists in recent years to discover the mechanism of action of various antioxidants. The idea that fruit and vegetable consumption alone is associated with a decreased risk of cancer is yet to be determined. This chapter shows that antioxidants, as previously reported, contribute to prevent and treat many types of cancer, but their anticancer effects are not absolute and depend on the time, amount, and conditions of their administration to treat different cancers. It is important that physicians make an integrated decision, based on the following consideration: (1) the background and state of the patient, (2) the antioxidant dosage and types, and (3) type of cancer and antitumor therapy. In addition, it is necessary to examine the safety and viability of antioxidants in pathological conditions and cancer therapy and that trials be performed with a single regimen, single type of cancer, and single antioxidant.

*Antioxidants*
