Ovarian cancer (OvCa) is the fifth most common cause of death from all cancers among women in United Sates and the leading cause of death from gynecological malignancies. While most OvCa patients initially respond to surgical debulking and chemotherapy, 75% of patients later succumb to the disease. Thus, there is an urgent need to test novel therapeutic agents to counteract the high mortality rate associated with OvCa. In this context, we have developed and engineered Nanoceria (NCe), nanoparticles of cerium oxide, possessing anti-oxidant properties, to be used as a therapeutic agent in OvCa. We show for the first time that NCe significantly inhibited production of reactive oxygen species (ROS) in A2780 cells, attenuated growth factor (SDF1, HB-EGF, VEGF₁₆₅ and HGF) mediated cell migration and invasion of SKOV3 cells, without affecting the cell proliferation. NCe treatment also inhibited VEGF₁₆₅ induced proliferation, capillary tube formation, activation of VEGFR2 and MMP2 in human umbilical vascular endothelial cells (HUVEC). NCe (0.1 mg/kg body weigh) treatment of A2780 ovarian cancer cells injected intra-peritoneally in nude mice showed significant reduction (p<0.002) in tumor growth accompanied by decreased tumor cell proliferation as evident from reduced tumor size and Ki67 staining. Accumulation of NCe was found in tumors isolated from treated group using transmission electron microscopy (TEM) and inductively coupled plasma mass spectroscopy (ICP-MS). Reduction of the tumor mass was accompanied by attenuation of angiogenesis, as observed by reduced CD31 staining and specific apoptosis of vascular endothelial cells. Collectively, these results indicate that cerium oxide based NCe is a novel nanoparticle that can potentially be used as an anti-angiogenic therapeutic agent in ovarian cancer.

Earlier investigations have revealed that tumor cells undergo metabolic reprogramming and mainly derive their cellular energy from aerobic glycolysis rather than oxidative phosphorylation even in the presence of oxygen. However, recent studies have shown that certain cancer cells display increased oxidative phosphorylation or high metabolically active phenotype. Cellular bioenergetic profiling of 13 established and 12 patient derived ovarian cancer cell lines revealed significant bioenergetics diversity. The bioenergetics phenotype of ovarian cancer cell lines correlated with functional phenotypes of doubling time and oxidative stress. Interestingly, chemosensitive cancer cell lines (A2780 and PEO1) displayed a glycolytic phenotype while their chemoresistant counterparts (C200 and PEO4) exhibited a high metabolically active phenotype with the ability to switch between oxidative phosphorylation or glycolysis. The chemosensitive cancer cells could not survive glucose deprivation, while the chemoresistant cells displayed adaptability. In the patient derived ovarian cancer cells, a similar correlation was observed between a high metabolically active phenotype and chemoresistance. Thus, ovarian cancer cells seem to display heterogeneity in using glycolysis or oxidative phosphorylation as an energy source. The flexibility in using different energy pathways may indicate a survival adaptation to achieve a higher ‘cellular fitness’ that may be also associated with chemoresistance.

Tumor-associated macrophages (TAMs) affect cancer progression and therapy. Ovarian carcinoma often metastasizes to the peritoneal cavity. Here, we found 2 peritoneal macrophage subsets in mice bearing ID8 ovarian cancer based on T cell immunoglobulin and mucin domain containing 4 (Tim-4) expression. Tim-4 ⁺ TAMs were embryonically originated and locally sustained while Tim-4 ^– TAMs were replenished from circulating monocytes. Tim-4 ⁺ TAMs, but not Tim-4 ^– TAMs, promoted tumor growth in vivo. Relative to Tim-4 ^– TAMs, Tim-4 ⁺ TAMs manifested high oxidative phosphorylation and adapted mitophagy to alleviate oxidative stress. High levels of arginase-1 in Tim-4 ⁺ TAMs contributed to potent mitophagy activities via weakened mTORC1 activation due to low arginine resultant from arginase-1–mediated metabolism. Furthermore, genetic deficiency of autophagy element FAK family-interacting protein of 200 kDa resulted in Tim-4 ⁺ TAM loss via ROS-mediated apoptosis and elevated T cell immunity and ID8 tumor inhibition in vivo. Moreover, human ovarian cancer–associated macrophages positive for complement receptor of the immunoglobulin superfamily (CRIg) were transcriptionally, metabolically, and functionally similar to murine Tim-4 ⁺ TAMs. Thus, targeting CRIg ⁺ (Tim-4 ⁺ ) TAMs may potentially treat patients with ovarian cancer with peritoneal metastasis.

Nanomedicine is a very promising field and nanomedical drugs have recently been used as therapeutic agents against cancer. In a previous study, we showed that Nanoceria (NCe), nanoparticles of cerium oxide, significantly inhibited production of reactive oxygen species, cell migration and invasion of ovarian cancer cells in vitro, without affecting cell proliferation and significantly reduced tumor growth in an ovarian cancer xenograft nude model. Increased expression of folate receptor-α, an isoform of membrane-bound folate receptors, has been described in ovarian cancer. To enable NCe to specifically target ovarian cancer cells, we conjugated nanoceria to folic acid (NCe-FA). Our aim was to investigate the pre-clinical efficacy of NCe-FA alone and in combination with Cisplatin. Ovarian cancer cell lines were treated with NCe or NCe-FA. Cell viability was assessed by MTT and colony forming units. In vivo studies were carried in A2780 generated mouse xenografts treated with 0.1 mg/Kg NCe, 0.1 mg/Kg; NCe-FA and cisplatinum, 4 mg/Kg by intra-peritoneal injections. Tumor weights and burden scores were determined. Immunohistochemistry and toxicity assays were used to evaluate treatment effects. We show that folic acid conjugation of NCe increased the cellular NCe internalization and inhibited cell proliferation. Mice treated with NCe-FA had a lower tumor burden compared to NCe, without any vital organ toxicity. Combination of NCe-FA with cisplatinum decreased the tumor burden more significantly. Moreover, NCe-FA was also effective in reducing proliferation and angiogenesis in the xenograft mouse model. Thus, specific targeting of ovarian cancer cells by NCe-FA holds great potential as an effective therapeutic alone or in combination with standard chemotherapy.

Metastasis is an intricate process by which a small number of cancer cells from the primary tumor site undergo numerous alterations, which enables them to form secondary tumors at another and often multiple sites in the host. Transition of a cancer cell from epithelial to mesenchymal phenotype is thought to be the first step in the progression of metastasis. Recently, the recognition of cancer stem cells has added to the perplexity in understanding metastasis, as studies suggest cancer stem cells to be the originators of metastasis. All current and investigative drugs have been unable to prevent or reverse metastasis, as a result of which most metastatic cancers are incurable. A potential drug that can be considered is metformin, an oral hypoglycemic drug. In this review we discuss the potential of metformin in targeting both epithelial to mesenchymal transition and cancer stem cells in combating cancer metastases.

Omental adipocytes promote ovarian cancer by secretion of adipokines, cytokines and growth factors, and acting as fuel depots. We investigated if metformin modulates the ovarian cancer promoting effects of adipocytes. Effect of conditioned media obtained from differentiated mouse 3T3L1 preadipoctes on the proliferation and migration of a mouse ovarian surface epithelium cancer cell line (ID8) was estimated. Conditioned media from differentiated adipocytes increased the proliferation and migration of ID8 cells, which was attenuated by metformin. Metformin inhibited adipogenesis by inhibition of key adipogenesis regulating transcription factors (CEBPα, CEBPß, and SREBP1), and induced AMPK. A targeted Cancer Pathway Finder RT-PCR (real-time polymerase chain reaction) based gene array revealed 20 up-regulated and 2 down-regulated genes in ID8 cells exposed to adipocyte conditioned media, which were altered by metformin. Adipocyte conditioned media also induced bio-energetic changes in the ID8 cells by pushing them into a highly metabolically active state; these effects were reversed by metformin. Collectively, metformin treatment inhibited the adipocyte mediated ovarian cancer cell proliferation, migration, expression of cancer associated genes and bio-energetic changes. Suggesting, that metformin could be a therapeutic option for ovarian cancer at an early stage, as it not only targets ovarian cancer, but also modulates the environmental milieu.