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Stonington, ME, United States

Ma X.,University of Maryland, Baltimore | Kundu N.,University of Maryland, Baltimore | Collin P.D.,Coastside Bio Resources | Goloubeva O.,University of Maryland, Baltimore | And 2 more authors.
Breast Cancer Research and Treatment | Year: 2012

Frondoside A, derived from the sea cucumber Cucumaria frondosa has demonstrable anticancer activity in several models, however, the ability of Frondoside A to affect tumor metastasis has not been reported. Using a syngeneic murine model of metastatic breast cancer, we now show that Frondoside A has potent antimetastatic activity. Frondoside A given i.p. to mice bearing mammary gland-implanted mammary tumors, inhibits spontaneous tumor metastasis to the lungs. The elevated Cyclooxygenase-2 activity in many malignancies promotes tumor growth and metastasis by producing high levels of PGE2 which acts on the prostaglandin E receptors, chiefly EP4 and EP2. We examined the ability of Frondoside A to modulate the functions of these EP receptors. We now show that Frondoside A antagonizes the prostaglandin E receptors EP2 and EP4. 3H-PGE 2 binding to recombinant EP2 or EP4-expressing cells was inhibited by Frondoside A at low μM concentrations. Likewise, EP4 or EP2-linked activation of intracellular cAMP as well as EP4-mediated ERK1/2 activation were also inhibited by Frondoside A. Consistent with the antimetastatic activity observed in vivo, migration of tumor cells in vitro in response to EP4 or EP2 agonists was also inhibited by Frondoside A. These studies identify a new function for an agent with known antitumor activity, and show that the antimetastatic activity may be due in part to a novel mechanism of action. These studies add to the growing body of evidence that Frondoside A may be a promising new agent with potential to treat cancer and may also represent a potential new modality to antagonize EP4. © Springer Science+Business Media, LLC. 2011.

Holt D.M.,University of Maryland, Baltimore | Ma X.,University of Maryland, Baltimore | Kundu N.,University of Maryland, Baltimore | Collin P.D.,Coastside Bio Resources | And 2 more authors.
Journal of Immunotherapy | Year: 2012

Breast malignancies often have high levels of COX-2. The COX-2 product prostaglandin E 2 (PGE 2) contributes to the high metastatic capacity of breast tumors. Our published data indicate that inhibiting either PGE 2 production or PGE 2-mediated signaling through the PGE 2 receptor EP4 (1 of 4 EP expressed on the malignant cell) reduces metastasis by a mechanism that requires natural killer (NK) cells. Tumor-derived PGE 2 and exogenous PGE 2 are known to have direct inhibitory effects on NK cell functions, but less is known regarding which EP receptors mediate these effects. We now show that several NK functions (lysis, migration, cytokine production) are compromised in tumor-bearing mice and that tumor-produced PGE 2 interferes with NK cell functions. PGE 2 inhibits the potential of NK cells to migrate, exert cytotoxic effects, and secrete interferon γ. The ability of PGE 2 to inhibit NK cells from tumor-bearing mice is by acting on EP2 and EP4 receptors. NK cells from tumor-bearing mice were more sensitive to inhibition by EP4 and EP2 agonists compared with endogenous NK cells from healthy mice. PGE 2 was inhibitory to most NK functions of either normal or tumor-bearing mice. In contrast, there was a trend for enhanced tumor necrosis factor α production in response to PGE 2 by NK cells from tumor-bearing mice. We also report that a recently described EP4 antagonist, frondoside A, inhibits breast tumor metastasis in an NK-dependent manner and protects interferon γ production by NK cells from PGE 2-mediated suppression. Taken together these data show that NK functions are depressed in tumor-bearing hosts relative to normal NK cells and that PGE 2 suppresses NK functions by acting on EP2 and EP4 receptors. Copyright © 2012 by Lippincott Williams & Wilkins.

Attoub S.,United Arab Emirates University | Arafat K.,United Arab Emirates University | Gelaude A.,Ghent University | Al Sultan M.A.,United Arab Emirates University | And 5 more authors.
PLoS ONE | Year: 2013

A major challenge for oncologists and pharmacologists is to develop less toxic drugs that will improve the survival of lung cancer patients. Frondoside A is a triterpenoid glycoside isolated from the sea cucumber, Cucumaria frondosa and was shown to be a highly safe compound. We investigated the impact of Frondoside A on survival, migration and invasion in vitro, and on tumor growth, metastasis and angiogenesis in vivo alone and in combination with cisplatin. Frondoside A caused concentration-dependent reduction in viability of LNM35, A549, NCI-H460-Luc2, MDA-MB-435, MCF-7, and HepG2 over 24 hours through a caspase 3/7-dependent cell death pathway. The IC50 concentrations (producing half-maximal inhibition) at 24 h were between 1.7 and 2.5 μM of Frondoside A. In addition, Frondoside A induced a time- and concentration-dependent inhibition of cell migration, invasion and angiogenesis in vitro. Frondoside A (0.01 and 1 mg/kg/day i.p. for 25 days) significantly decreased the growth, the angiogenesis and lymph node metastasis of LNM35 tumor xenografts in athymic mice, without obvious toxic side-effects. Frondoside A (0.1-0.5 μM) also significantly prevented basal and bFGF induced angiogenesis in the CAM angiogenesis assay. Moreover, Frondoside A enhanced the inhibition of lung tumor growth induced by the chemotherapeutic agent cisplatin. These findings identify Frondoside A as a promising novel therapeutic agent for lung cancer. © 2013 Attoub et al.

Kundu N.,University of Maryland, Baltimore | Ma X.,University of Maryland, Baltimore | Kochel T.,University of Maryland, Baltimore | Goloubeva O.,University of Maryland, Baltimore | And 7 more authors.
Breast Cancer Research and Treatment | Year: 2014

The cyclooxygenase pathway is strongly implicated in breast cancer progression but the role of this pathway in the biology of breast cancer stem/progenitor cells has not been defined. Recent attention has focused on targeting the cyclooxygenase 2 (COX-2) pathway downstream of the COX-2 enzyme by blocking the activities of individual prostaglandin E (EP) receptors. Prostaglandin E receptor 4 (EP4) is widely expressed in primary invasive ductal carcinomas of the breast and antagonizing this receptor with small molecule inhibitors or shRNA directed to EP4 inhibits metastatic potential in both syngeneic and xenograft models. Breast cancer stem/progenitor cells are defined as a subpopulation of cells that drive tumor growth, metastasis, treatment resistance, and relapse. Mammosphere-forming breast cancer cells of human (MDA-MB-231, SKBR3) or murine (66.1, 410.4) origin of basal-type, Her-2 phenotype and/or with heightened metastatic capacity upregulate expression of both EP4 and COX-2 and are more tumorigenic compared to the bulk population. In contrast, luminal-type or non-metastatic counterparts (MCF7, 410, 67) do not increase COX-2 and EP4 expression in mammosphere culture. Treatment of mammosphere-forming cells with EP4 inhibitors (RQ-15986, AH23848, Frondoside A) or EP4 gene silencing, but not with a COX inhibitor (Indomethacin) reduces both mammosphere-forming capacity and the expression of phenotypic markers (CD44 hi/CD24low, aldehyde dehydrogenase) of breast cancer stem cells. Finally, an orally delivered EP4 antagonist (RQ-08) reduces the tumor-initiating capacity and markedly inhibits both the size of tumors arising from transplantation of mammosphere-forming cells and phenotypic markers of stem cells in vivo. These studies support the continued investigation of EP4 as a potential therapeutic target and provide new insight regarding the role of EP4 in supporting a breast cancer stem cell/tumor-initiating phenotype. © 2013 The Author(s).

Coastside Bio Resources | Date: 2009-11-17

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