**3. Antitumor effects of Ivermectin-mechanisms of action and** *in vitro* **data**

Ivermectin has demonstrated antitumor effects in different types of cancers. Among mechanisms of action reported, ivermectin interacts and affects the function of 1) mitochondrial I complex, the multidrug resistance protein (MDR), 2) RNA helicases, 3) the WNT-TCF pathway, 4) chloride channel receptor, 5) immunogenic cell death via ATP- and HMGB1, 6) PAK-1, 7,8) epigenetic signature and sel-renewal of stem cells [10]. Preclinical testing have demonstrated inhibition of cell growth, induction of apoptosis in different cancer cell lines and antitumor effects in murine models (**Figure 1**) [11–19]. The *in vitro* antitumor effects are observed at a median concentration of 5 μM (0.01–100 μM), which is clinically attainable according to the pharmacokinetic data in humans shown in **Table 1**. We present a review of the laboratory results of ivermectin on various cancer cell lines below.

#### **3.1 Ovarian cancer**

Ivermectin blocks the oncogenic kinase PAK1 in human ovarian cancer and in NF2-deficient Schwannoma cell lines to suppress their PAK1-dependent growth in cell culture at a half maximal inhibitory concentration (IC50) between 5 and

*Ivermectin: Potential Repurposing of a Versatile Antiparasitic as a Novel Anticancer DOI: http://dx.doi.org/10.5772/intechopen.99813*

#### **Figure 1.**

*Cancer targets of ivermectin. 1. Decreasing the function of the mitochondrial complex I, Ivermectin, limits the electronic movement in the oxidative phosphorylation pathway that stimulates oxygen consumption rate to generate ATP for the cell. Low ATP levels are related to a failure in the P-glycoprotein pump to extrude chemotherapy drugs. Concomitantly there is a reduction in the phosphorylation levels of Akt, impacting the mitochondrial biogenesis process. Furthermore, alterations in the mitochondrial machinery are related to increased levels of reactive oxygen species that damage DNA. 2. Ivermectin limits the function of the RNA helicases NS3 and DDX23, both of which are related to ribosome biogenesis and post-transcriptional modifications, as well as with mRNA degradation. DDX23 acts as a promoter of miR-21, which is a wellrecognized stimulator of tumor progression. 3. The WNT-TCF pathway, involved in cancer progression and metastases, is inhibited by Ivermectin. Indeed, this compound represses AXIN2, LGR5, and ASCL2, all of them WNT-TCF targets. At the same time, it promotes the repressor of the WNT signaling FILIP1L. Both effects inhibit the ability of WNT-TCF to downregulate the tumor suppressor APC and limit the translocation of β–catenin to the nucleus for epithelial to mesenchymal transition in metastatic events. 4. Ivermectin acts as an ionophore by the up-regulation of chloride channels to generate apoptosis and osmotic cell death. 5. Ivermectin induces immunogenic cell death by stimulating an ATP- and HMGB1-enriched microenvironment, which promotes inflammation. This drug also increases ATP sensitivity and calcium signals in P2X membranal receptors, particularly P2X4 and P2X7, to induce ATP-dependent immune responses. 6. Ivermectin promotes the poly-ubiquitination of the kinase PAK1, which directs it to degradation in the proteasome. Defective PAK1, in turn, inhibits the Akt/mTOR pathway. At the same time, Ivermectin stimulates the expression of Beclin1 and Atg5, both related to induction of autophagy. Particularly, Beclin1 increases the expression of the positive autophagy regulators Atg14L and Vps34 and reduces the negative regulator of apoptosis Bcl-2. Together, this generates autophagy and apoptosis. 7,8. Ivermectin modifies the epigenetic signature and the self-renewal activity in the malignant cell due to its ability to mimic the SIN3-interaction that binds to the PAH2 motif of the ca.*


**Table 1.**

*Adverse effects caused by Ivermectin.*

20 μM [14]. PAK1 is involved in various signaling pathways that play an essential role in cytoskeletal dynamics, cell adhesion, migration, proliferation, apoptosis, and mitosis. It is required for the growth of approximately 70% of neoplasms [20]. Additionally, cancer stem-like cells derived from SKOV-3 cell line treated with 5 μM ivermectin showed a significant decrease in cell viability and clonogenic capacity. Also, the expression levels of Nanog, Sox2, and Oct4 are reduced after treatment with ivermectin 5 μM [11].

### **3.2 Breast cancer**

Ivermectin inhibits the ATK/mTOR pathway in breast cancer cell lines by promoting ubiquitination of PAK1. Ivermectin disrupts the binding of PAK1 protein with AKT, and in turn hinders the phosphorylation and activation of AKT; resulting in AKT/mTOR pathway inactivation. These effects of ivermectin are observed at concentrations above 10 μM [15]. Additionally, ivermectin preferentially inhibits the viability of cancer stem-like cells enriched populations (CD44+/ CD24−) in the range of 0.2–8 μM via reducing the expression of maintenance of the pluripotency and self-renewal markers Nanog, Oct4, and Sox2 at both mRNA and protein levels [11]. Separately, a study demonstrated that 1 μM ivermectin treatment inhibits the function of SIN3 [16], which is part of a complex that positively regulates Nanog and Sox2, leading to a decrease in mammospheres number [21]. Furthermore, ivermectin was reported to induce E-cadherin and Estrogen Receptor 1 expression and the restoration of tamoxifen sensitivity in a triple-negative breast cancer model. According to these observations, ivermectin has potential antitumor effects in triple-negative breast cancer [16]. Another study demonstrated a synergy between ivermectin with docetaxel or cyclophosphamide in estrogen receptor-negative breast cancer cells and a synergistic effect with tamoxifen in estrogen receptorpositive breast cancer cell lines [22].

#### **3.3 Liver cancer**

In human combined hepatocellular-cholangiocarcinomas and intrahepatic cholangiocarcinomas (cHC-CCs and ICCs), there is robust YAP1 activation. YAP1 is a transcriptional regulator of genes involved in cell proliferation and suppression of apoptotic genes, and itis inhibited in the Hippo signaling pathway which allows tumor suppression. Nuclear translocation of YAP1/TAZ also increases transcription of TGF-βs [23]. Thus, it is possible that coordinated targeting of YAP1/TAZ and TGF-β signaling may be a treatment for cHC-CCs and ICCs displaying dysregulated Hippo signaling and meanwhile drug screening revealed ivermectin to inhibit YAP1 activation [23].

*Ivermectin: Potential Repurposing of a Versatile Antiparasitic as a Novel Anticancer DOI: http://dx.doi.org/10.5772/intechopen.99813*
