*2.1.7. HCC and bile duct carcinoma (cholangiocarcinoma)*

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy, which is the sixth most common type of cancer worldwide. Sorafenib, a known multikinase inhibitor, can extend the survival rate of patients with advanced HCC. ATO was reported to synergize with sorafenib to inhibit the proliferation and promote the apoptosis of HCC cells by diminishing the sorafenib-induced activation of Akt and/or its downstream factors, including glycogen synthase kinase-3β, mTOR, ribosomal protein S6 kinase, and eukaryotic translation initiation factor 4E-binding protein 1 [28]. ATO was also reported to potentiate the anticancer effect of genistein [29], 3′-azido-3′-deoxythymidine (AZT) [30], oridonin [31], MDM2 inhibitor nutlin-3 [32], metformin [33–34], survivin mutant (T34A) [35], shikonin [36], and andrographolide [37] in HCC cells.

#### *2.1.8. Lung cancer*

are the most standard therapies for OSCC. Since ATO/CDDP-induced apoptosis was almost completely abrogated by NAC, ROS generation may be closely associated with the tumor suppression effect (**Figure 1A**) [12]. Recent publications also implicated the therapeutic application of arsenic in the treatment for OSCC. Wang et al. reported that nicotinamide phosphoribosyltransferase (NAMPT) increases in patients with OSCC and a NAMPT inhibitor FK866 and ATO cooperatively induced apoptosis and depletes intracellular nicotinamide adenine dinucleotide levels in OSCC cell lines [13]. Tsai et al. showed that the combined ATO-dithiothreitol (DTT) treatment increases proapoptotic molecules Bax and Bak and decreases Bcl-2 and p53, which

The rate of the mortality from ovarian cancer is highest among malignant tumors of the female genital organs. As indicated in other types of cancer, ATO was reported to exert synergistic cytotoxic effects against ovarian cancer cells when it was combined with CDDP, one of the standard chemotherapeutics for ovarian cancer, and/or mTOR inhibitor RAD001 [15, 16]. Ong et al. reported that both buthionine sulfoximine and ascorbic acid differentially enhance ATO-mediated cell killing by mediating GSH depletion and the oxidative stress-related pathway, respectively [17].

Radiotherapy has been generally used for the treatment of patients with cervical cancer, which is the most common cancer among females worldwide, as a monotherapy and combined therapy with chemotherapeutics, such as platinum-based drugs. The combined ATO-radiation treatment was expectably reported to exert a beneficial antitumoral effect on cervical cancer cells in vitro and/or in vivo [18, 19]. Wei et al. reported that ATO decreases radiation-accelerated lung metastases probably via suppression of radiation-induced MMP-9 expression [18]. Kang et al. reported that ATO enhances the translocation of Bax protein to mitochondria and the phosphorylation level of Bcl-2, which were accompanied by activation of MAPKs including p38 and JNK [19]. Since NAC clearly inhibits the ATO-mediated cell killing as well as MAPK activation, ROS generation may play an important role in ATO-radiation-induced apoptosis. In

O6

effect on cervical cancer cells. Kim et al. reported that the combined TAO and radachlorin/photodynamic therapy cooperatively suppress the proliferation of mouse TC-1 cells both in vitro and in vivo, where tumor suppressor p53 and the inducible p21 protein increased especially in combined treated tumor cells [20]. TAO was also reported to synergistically suppress tumor growth of human cervical carcinoma cell line CaSki when it was combined with CDDP [21]. The combined TAO-CDDP therapy dramatically increased the number of apoptotic cells, as similarly observed in other types of cancer cells when ATO was combined with CDDP [12, 15].

Breast cancer is one of the leading causes of cancer-related deaths among women worldwide. In breast cancer cells, ATO was reported to reduce the expression of DNA methyltransferase-1 (DNMT1) and to induce the expression of estrogen receptor α (ERα), whose expression has been epidemiologically recognized to increase disease-free survival and indicate an overall

) was shown to potentially exert an anticancer

leads to a significant cell death of oral cancer cells but not the non-tumor cells [14].

*2.1.4. Ovarian cancer*

38 Current Understanding of Apoptosis - Programmed Cell Death

*2.1.5. Cervical cancer*

*2.1.6. Breast cancer*

addition to ATO, tetraarsenic oxide (TAO, As<sup>4</sup>

Lung cancer is the most common type of cancer worldwide. As indicated in colon cancer, there are several reports regarding the synergistic induction of apoptosis by an NSAID sulindac and ATO in human lung cancer cell lines [38, 39]. Combined ATO-sulindac treatment induced apoptosis of human non-small cell lung cancer (NSCLC) cell line A549 by mediating the mitochondrial pathway and the NF-κB pathway [38] and by mediating p53-induced downregulation of survivin [39]. It has also been reported that combined ATO-sulindac treatment induces synergistic augmentation of cytotoxicity in both human NSCLC cell lines NCI-H157 and NCI-H1299 by mediating ROS-induced MAPK phosphorylation and via c-Jun NH<sup>2</sup> -terminal kinase-dependent Bcl-xL phosphorylation, respectively [40, 41]. Indomethacin, a nonselective cyclooxygenase inhibitor (a structural isoform of sulindac), was also shown to enhance the ATO-induced cytotoxic effect in A549 cells by mediating activation of ERK and/or p38 MAPKs [42]. Han et al. reported that buthionine sulfoximine (BSO), a glutathione synthesis inhibitor, enhances ATOinduced apoptosis in A549 cells, in which the apoptosis was related to the increased level of intracellular ROS (**Figure 1A**) [43]. In addition, combined ATO-CDDP treatment induced apoptosis and synergistically suppressed the proliferation of human NSCLC cell lines A549 and H460, with CI values 0.5 and 0.6, respectively, where CI <1 defines synergism [44]. Lam et al. indicated that combined treatment with ATO and a selective fibroblast growth factor receptor (FGFR) inhibitor PD173074 cooperatively suppresses tumor proliferation both in vitro and in vivo in the lung squamous cell carcinoma (SCC) cell line SK-MES-1, in which ATO-PD173074 decreased FGFR1, Akt, Src, c-Raf, and Erk, at least in part by mediating proteasomal degradation [45]. Gu et al. reported that ROS-mediated ER stress and mitochondrial dysfunction were involved in the apoptosis induced by resveratrol and ATO in A549 cells [46].

ATO-radiation combination treatment enhanced autophagic effects in U118-MG cells through increased mitotic arrest and regulation of PI3K/Akt and ERK1/2 signaling pathways [53]. Similar observations were reported in human fibrosarcoma and osteosarcoma, where the combined

Arsenic-Based Anticancer-Combined Therapy: Novel Mechanism Inducing Apoptosis of Cancer…

oxygenase-1 (HO-1) is known to be increased in arsenic-treated cells [56]. Liu et al. reported that HO-1 inhibition or Nrf2 knockdown significantly potentiated ATO-induced cytotoxic effects on glioma cells [57]. This result suggests that ATO-induced gene expression including the Nrf2 signaling pathway may be partly involved in the resistance of cancer cells to ATO. Dizaji et al. reported that combined treatment with ATO and silibinin, a natural polyphenolic flavonoid, synergistically induces apoptosis and inhibits invasiveness in the human GBM cell line U87MG, in which the expression of cathepsin B, uPA, MMP-2, MMP-9, membrane type 1-MMP, survivin, Bcl-2, and CA9 decreased after treatment [58]. Gülden et al. reported that combined treatment with ATO and silibinin reduces the viability of A-172 by mediating intracellular arsenic accumulation [59]. As described in lung cancer, BSO depleted cellular glutathione and acted synergistically with ATO in rat C6 astroglioma cells [60]. Karsy et al. investigated the effect of ATO and ATRA on neurosphere formation of U87MG possessing wild-type (wt) p53 and/ or codon-specific p53 mutant (R273H) [61]. They found that ATO and ATRA treatment could induce apoptosis of both U87-p53 (wt) and U87-p53 (R273H) and could potently suppress CSC properties in vitro [61]. It is well known that c-Myc is also required for the maintenance of CSCs of various cancers including GBM [62]. Yoshimura et al. showed that ATO and c-Myc inhibitor 10058-F4 coordinately enhanced differentiation of GBM CSCs and regressed GBM CSC tumor growth in vivo [63]. Primon et al. reported the involvement of cathepsin L (CatL) in the ATOinduced apoptotic effect [64, 65]. They found that knockdown of CatL enhances ATO-mediated in vitro cytotoxicity and apoptosis in both the GBM cell line U87MG [58] and pilocytic astrocy-

Baumgartner et al. reported that ATO-mediated apoptosis is markedly enhanced by using the polyunsaturated fatty acid docosahexaenoic acid (DHA) in 12 different ATO-resistant solid tumor cell lines including breast, ovarian, colon, prostate, cervical, and pancreatic cancer, while there was no cytotoxicity in normal skin fibroblasts, human microvascular endothelial cells, and peripheral blood mononuclear cells derived from healthy donors [66]. Lin et al. reported that combined ATRA and ATO treatment synergistically inhibits the proliferation and induces apoptosis in human hepatoma, breast cancer, and lung cancer cells in vitro [67]. Kryeziu et al. found that combined treatment with ATO and erlotinib, a selective EGFR inhibitor, acts synergistically through accumulation of DNA damage by inhibiting EGFR-mediated DNA double-strand break repair in mesothelioma, HCC, colorectal carcinoma, osteosarcoma,

Patients with newly diagnosed APL, also known as a AML M3 subtype with APL-specific chromosomal translocation t(15;17) (q22;q21) and PML/RARα chimeric fusion protein, are mostly

/M phase [54, 55]. ATO is a ROS inducer, and heme

http://dx.doi.org/10.5772/intechopen.74824

41

treatment arrested their cell cycle at the G2

toma cell line MPA58 [65].

*2.1.13. Other combinations*

thyroid carcinoma, and cervix carcinoma in vitro [68].

**2.2. Hematological malignancies**

*2.2.1. Acute promyelocytic leukemia (APL)*
