Introduction: Honokiol, a small-molecule polyphenol isolated from magnolia species, is widely known for its therapeutic potential as an antiinflammatory, antithrombosis, and antioxidant agent, and more recently, for its protective function in the pathogenesis of carcinogenesis. In the present study, we sought to examine the effectiveness of honokiol in inhibiting migration and invasion of breast cancer cells and to elucidate the underlying molecular mechanisms. Methods: Clonogenicity and three-dimensional colony-formation assays were used to examine breast cancer cell growth with honokiol treatment. The effect of honokiol on invasion and migration of breast cancer cells was evaluated by using Matrigel invasion, scratch-migration, spheroid-migration, and electric cell-substrate impedance sensing (ECIS)-based migration assays. Western blot and immunofluorescence analysis were used to examine activation of the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) axis. Isogenic LKB1-knockdown breast cancer cell line pairs were developed. Functional importance of AMPK activation and LKB1 overexpression in the biologic effects of honokiol was examined by using AMPK-null and AMPK-wild type (WT) immortalized mouse embryonic fibroblasts (MEFs) and isogenic LKB1-knockdown cell line pairs. Finally, mouse xenografts, immunohistochemical and Western blot analysis of tumors were used. Results: Analysis of the underlying molecular mechanisms revealed that honokiol treatment increases AMP-activated protein kinase (AMPK) phosphorylation and activity, as evidenced by increased phosphorylation of the downstream target of AMPK, acetyl-coenzyme A carboxylase (ACC) and inhibition of phosphorylation of p70S6kinase (pS6K) and eukaryotic translation initiation factor 4E binding protein 1 (4EBP1). By using AMPK-null and AMPK-WT (MEFs), we found that AMPK is required for honokiol-mediated modulation of pACC-pS6K. Intriguingly, we discovered that honokiol treatment increased the expression and cytoplasmic translocation of tumor-suppressor LKB1 in breast cancer cells. LKB1 knockdown inhibited honokiol-mediated activation of AMPK and, more important, inhibition of migration and invasion of breast cancer cells. Furthermore, honokiol treatment resulted in inhibition of breast tumorigenesis in vivo. Analysis of tumors showed significant increases in the levels of cytoplasmic LKB1 and phospho-AMPK in honokiol-treated tumors. Conclusions: Taken together, these data provide the first in vitro and in vivo evidence of the integral role of the LKB1-AMPK axis in honokiol-mediated inhibition of the invasion and migration of breast cancer cells. In conclusion, honokiol treatment could potentially be a rational therapeutic strategy for breast carcinoma.

Hepatocellular carcinoma (HCC) incidence, as well as related mortality, has been steadily increasing in the USA and across the globe, partly due to the lack of effective therapeutic options for advanced HCC. Though sorafenib is considered standard-of-care for advanced HCC, it only improves median survival by a few months when compared to placebo. Sorafenib is also associated with several unpleasant side effects that often lead to early abatement of therapy. Here, we investigate whether a combination regimen including low-dose sorafenib and a non-toxic dose of anti-diabetic drug metformin can achieve effective inhibition of HCC. Indeed, combining metformin with low-dose sorafenib inhibited growth, proliferation, migration, and invasion potential of HCC cells. We observed a 5.3- and 1.9-fold increase in sub-G1 population in the combination treatment compared to sorafenib alone. We found that the combination of metformin enhanced the efficacy of sorafenib and inhibited the MAPK/ERK/Stat3 axis. Our in vivo studies corroborated the in vitro findings, and mice harboring HepG2-derived tumors showed effective tumor reduction upon treatment with low-dose sorafenib and metformin combination. This work sheds light on a therapeutic strategy aiming to augment sorafenib efficacy or dose-de-escalation that may prove beneficial in circumventing sorafenib resistance as well as minimizing related side effects.

Obese women with hormone receptor-positive breast cancer exhibit poor response to therapy and inferior outcomes. However, the underlying molecular mechanisms by which obesity/hyperleptinemia may reduce the efficacy of hormonal therapy remain elusive. Obese mice with hyperleptinemia exhibit increased tumor progression and respond poorly to tamoxifen compared to non-obese mice. Exogenous leptin abrogates tamoxifen-mediated growth inhibition and potentiates breast tumor growth even in the presence of tamoxifen. Mechanistically, leptin induces nuclear translocation of phosphorylated-ER and increases the expression of ER-responsive genes, while reducing tamoxifen-mediated gene repression by abrogating tamoxifen-induced recruitment of corepressors NCoR, SMRT, and Mi2 and potentiating coactivator binding. Furthermore, in silico analysis revealed that coactivator Med1 potentially associates with 48 (out of 74) obesity-signature genes. Interestingly, leptin upregulates Med1 expression by decreasing miR-205, and increases its functional activation via phosphorylation, which is mediated by activation of Her2 and EGFR. It is important to note that Med1 silencing abrogates the negative effects of leptin on tamoxifen efficacy. In addition, honokiol or adiponectin treatment effectively inhibits leptin-induced Med1 expression and improves tamoxifen efficacy in hyperleptinemic state. These studies uncover the mechanistic insights how obese/hyperleptinemic state may contribute to poor response to tamoxifen implicating leptin-miR205-Med1 and leptin-Her2-EGFR-Med1 axes, and present bioactive compound honokiol and adipocytokine adiponectin as agents that can block leptin’s negative effect on tamoxifen.

Jaboticaba peel (Myrciaria jaboticaba) is a source of bioactive compounds. We investigated the anticancer activity of ethyl acetate extract (JE1) and hydroethanolic extract (JE2) of Jaboticaba peel against breast cancer. Both JE1 and JE2 inhibited clonogenic potential of MDA-MB-231 cells while JE1 was particularly effective in MCF7 cells. Anchorage-independent growth and cell viability was also inhibited by JE1 and JE2. In addition to growth inhibition, JE1 and JE2 could also inhibit migration and invasion of cells. Interestingly, JE1 and JE2 show selective inhibition towards certain breast cancer cells and biological processes. Mechanistic evaluations showed that JE1 induced PARP cleavage, BAX and BIP indicating apoptotic induction. An elevation of phosphorylated ERK was observed in MCF7 cells in response to JE1 and JE2 along with increased IRE-α and CHOP expression indicating increased endoplasmic stress. Therefore, Jaboticaba peel extracts could be potentially considered for further development for breast cancer inhibition.

Optic neuropathies cause irreversible vision loss. Transplantation of pluripotent stem cell (PSC)–derived retinal ganglion cells (RGCs) offers one potential therapeutic avenue to restore vision in patients suffering from optic neuropathies if the donor neurons survive long term in the recipient eye and develop synaptic connections in the retinal inner plexiform layer (IPL) and subcortical visual centers, which has been difficult to achieve. Previous work in mouse retinal explant cultures has shown that enzymatic digestion of the retinal internal limiting membrane (ILM) promotes migration of transplanted RGCs into the recipient retina. Here, we examined donor RGC survival and engraftment in immunosuppressed mice, rats, and rhesus macaques and in postmortem human retinal explant cultures. Using three separate human PSC lines and three independent methods of ILM disruption (including enzymatic, developmental, and mechanical approaches), we demonstrated that the ILM is a barrier to retinal engraftment of intravitreally delivered human PSC-derived RGCs. Across models, ILM disruption was associated with greater donor RGC survival over 2 to 8 weeks and enabled migration of donor neuronal somata into the endogenous RGC layer, where they elaborated dendrites into the IPL and extended axons that followed the course of the endogenous retinal nerve fiber layer into the optic nerve head, findings that were negligible with intact ILM. Further, ILM disruption enabled donor RGCs to synaptically integrate into IPL circuits, conferring light responsivity in rodents. These findings have important implications for enabling neuronal replacement therapies to restore vision in patients with optic neuropathy.