International Journal of Molecular Sciences Review Withaferin-A—A Natural Anticancer Agent with Pleitropic Mechanisms of Action In-Chul Lee 1 and Bu Young Choi 2,* 1 Department of Cosmetic science, Seowon University, Cheongju, Chungbuk 361-742, Korea; [email protected] 2 Department of Pharmaceutical Science & Engineering, Seowon University, Cheongju, Chungbuk 361-742, Korea * Correspondence: [email protected]; Tel.: +82-43-299-8411 Academic Editor: Ge Zhang Received: 18 January 2016; Accepted: 17 February 2016; Published: 4 March 2016 Abstract: Cancer, being the second leading cause of mortality, exists as a formidable health challenge. In spite of our enormous efforts, the emerging complexities in the molecular nature of disease progression limit the real success in finding an effective cancer cure. It is now conceivable that cancer is, in fact, a progressive illness, and the morbidity and mortality from cancer can be reduced by interfering with various oncogenic signaling pathways. A wide variety of structurally diverse classes of bioactive phytochemicals have been shown to exert anticancer effects in a large number of preclinical studies. Multiple lines of evidence suggest that withaferin-A can prevent the development of cancers of various histotypes. Accumulating data from different rodent models and cell culture experiments have revealed that withaferin-A suppresses experimentally induced carcinogenesis, largely by virtue of its potent anti-oxidative, anti-inflammatory, anti-proliferative and apoptosis-inducing properties. Moreover, withaferin-A sensitizes resistant cancer cells to existing chemotherapeutic agents. The purpose of this review is to highlight the mechanistic aspects underlying anticancer effects of withaferin-A. Keywords: withaferin-A; phytochemical; cancer; chemoprevention; chemotherapy 1. Introduction Despite the development of a wide variety of anticancer drugs, the global incidence of various cancers, and the mortality thereof, is still on the rise. The number of cancer-related deaths is presumed to increase by two-fold in the next 50 years [1]. The increasing trend of chemotherapy resistance and frequent relapse of certain tumors make it more complicated to eradicate cancer by using conventional chemotherapeutic agents. Thus, there is always a need for developing new anticancer therapies to combat this dreadful disease. Plants have always been at the fore-front of new drug discovery. A large number of plant constituents, commonly known as phytochemicals, have gained the status of clinically used modern medicines, while many others have served as potential lead compounds for designing novel therapeutics [2]. In fact, plants are natural chemical factories for synthesizing chemicals with structural diversity, such as steroids, terpenoids, flavonoids, alkaloids, etc. Many of these plant secondary metabolites are biologically active, and can interact directly or indirectly with various cellular components, especially proteins and lipids, thereby reversing the altered functions of cancer cells [2,3]. Since the growth and development of tumors are triggered by oxidative stress and chronic inflammation, phytochemicals with antioxidative and anti-inflammatory properties are thought to play important roles in the prevention and/or treatment of cancer. Until now, numerous Int. J. Mol. Sci. 2016, 17, 290; doi:10.3390/ijms17030290 www.mdpi.com/journal/ijms Int. J. Mol. Sci. 2016, 17, 290 2 of 22 Int. J. Mol. Sci. 2016, 17, 290 2 of 21 phytochemicals have been examined for their potential anticancer properties by using a diverse array of preclinicalA large experimentalnumber of laboratory-based models. studies have demonstrated the anticancer effects of a medicinalA large plant, number Withania of laboratory-based somnifera (L.) Dual studies (Solanaceae), have demonstrated commonly theknown anticancer as Ashwagandha, effects of a medicinalIndian ginseng plant, orWithania Indian winter somnifera cherry(L.) Dual [4]. Different (Solanaceae), parts commonly of the plant known have long as Ashwagandha, been used in a Indian wide ginsengvariety of or Ayurvedic Indian winter formulations. cherry [ 4However,]. Different systematic parts of scientific the plant research have long on the been plant used begun in a in wide the variety1950s [5]. of AyurvedicThe anticancer formulations. property However,of W. sominefra systematic was first scientific addressed research by onDevi the and plant colleagues begun in the[6], 1950swho [showed5]. The anticancerthat intraper propertyitoneal of W.(i.p.) sominefra administrationwas first addressedof alcoholic byDevi root and extract colleagues of the [6 ],plant who showedcompletely that regressed intraperitoneal the growth (i.p.) administrationof sarcoma-180 of alcoholiccells inoculated root extract in nude of the mice. plant Subsequent completely regressedstudies have the growthdemonstrated of sarcoma-180 that the cells hydroalcoh inoculatedolic inroot nude extract mice. of Subsequent the plant studies attenuated have demonstrated20-methylcholathrene that the (20MC)-induced hydroalcoholic rootdevelopment extract of theof plantfibrosarcoma attenuated in 20-methylcholathreneBalb/C mice when (20MC)-inducedadministered intraperitoneally development of [7] fibrosarcoma or by gavage in Balb/C[8]. Davis mice and when Kuttan administered [9] have further intraperitoneally reported the [7] orinhibitory by gavage effect [8]. of Davis W. somnifera and Kuttan extract [9] haveon chemically further reported induced the mouse inhibitory skin effecttumor of development.W. somnifera extractAccording on to chemically a recent study, induced daily mouse administration skin tumor of development. root extract of According the plant markedly to a recent reduced study, dailymethylnitrosourea-induced administration of root rat extract mammary of the tumorige plant markedlynesis [10]. reduced These methylnitrosourea-induced anticancer properties of ratAshwagandha mammary tumorigenesisare attributable [10 to]. withanolides, These anticancer a cl propertiesass of bioactive of Ashwagandha constituents are isolated attributable from toW. withanolides,sominifera. Withaferin-A a class of (4β bioactive,5β,6β,22R constituents)-4,27-Dihydroxy-5,6-22,26-diepox isolated from W. sominiferayergosta-2,24-diene-1,26-di. Withaferin-A (4one,β,5 structureβ,6β,22R )-4,27-Dihydroxy-5,6-22,26-diepoxyergosta-2,24-diene-1,26-dishown in Figure 1), is the first antitumor withanolide that was one, isolated structure from shownleaves inof Figurethe plant1), back is the in first 1967 antitumor [8]. withanolide that was isolated from leaves of the plant back in 1967 [ 8]. Figure 1. Structure of withaferin-A. Pretreatment of Syrian golden hamstershamsters with withaferin-Awithaferin-A significantlysignificantly reduced 7,12-dimethylbenz(αα)anthracene)anthracene (DMBA)-induced (DMBA)-induced frequenc frequencyy of micronucleated polychromaticpolychromatic erythrocytes and chromosomal aberrations, indicating the antigenotoxic effect effect of of withaferin-A [11]. [11]. A greatgreat dealdeal ofof researchresearch hashas beenbeen conductedconducted toto elucidateelucidate thethe molecularmolecular mechanismsmechanisms underlyingunderlying anticancer effects of withaferin-A. This mini-reviewmini-review addresses the biochemical basis of antitumor potential of withaferin-A. 2. Effects Effects of of Withaferin-A Withaferin-A on on Multiorgan Multiorgan Carcinogenesis—Evidence Carcinogenesis—Evidence from Animal Model Studies Systematic researchresearch on on the the evaluation evaluation of anticancerof anticancer activities activities of withaferin-A of withaferin-A was started was aroundstarted thearound 1970s the [12 1970s]. Since [12]. then, Since a large then, number a large of studiesnumber have of demonstratedstudies have demonstrated the ability of withaferin-A the ability toof suppresswithaferin-A the in to vivo suppressgrowth the of in various vivo growth human of cancer various cells’ human xenograft cancer tumors cells’ xenograft as well as experimentallytumors as well inducedas experimentally carcinogenesis induced in different carcinogenesis rodent models in different [4]. Here, rodent we discuss models the [4]. chemopreventive Here, we discuss effects the of withaferin-Achemopreventive on organ-specific effects of withaferin-A carcinogenesis on organ-specificin vivo. carcinogenesis in vivo. 2.1. Sarcoma and Ascites Tumor 2.1. Sarcoma and Ascites Tumor In a pioneering study, Shohat and colleagues reported that i.p. administration of withaferin-A In a pioneering study, Shohat and colleagues reported that i.p. administration of withaferin-A reduced the growth of Ehrlich ascites tumor with an LD50 value of 400 mg/kg in Swiss albino mice [12] reduced the growth of Ehrlich ascites tumor with an LD50 value of 400 mg/kg in Swiss albino mice [12] and prolonged the survival of mouse sarcoma (S-180) and ascites tumor-bearing mice [13]. Electron and prolonged the survival of mouse sarcoma (S-180) and ascites tumor-bearing mice [13]. Electron microscopic analysis of implanted tumors revealed that treatment with withaferin-A altered the microscopic analysis of implanted tumors revealed that treatment with withaferin-A altered the spindle microtubule organization, suggesting a probable mechanism of tumor growth inhibition by the compound. Subsequent studies have reported that withaferin-A exerted inhibitory effects on the Int. J. Mol. Sci. 2016, 17, 290 3 of 22 spindle microtubule organization, suggesting a probable mechanism of tumor growth inhibition