Methyljasmonate, An Inhibitor of Glycolytic Energy Production, Displays Pre-Clinical Activity against Multiple Myeloma Cells.

In contrast to most normal cells, cancer cells typically produce energy predominantly by glycolysis as demonstrated by O. Warburg more than 50 years ago. Methyljasmonate (MJ), a hormone produced by plants in response to biotic & abiotic stresses such as herbivory and wounding, has been shown to prevent the interaction of hexokinase (Hxk) and voltage dependent anion channels (VDACs), thereby significantly impacting the onset of glycolytic energy production. This may explain promising preclinical results observed with MJ against a variety of cancer cells, including myeloid leukemia and B-cell lymphoma cell lines.

We tested the potential of MJ against Multiple Myeloma (MM) cells. We first evaluated the response of 16 different MM cell lines to 24 h of exposure to MJ concentrations of 0.5 – 3.5 mM using MTT assays. 15/16 of the MM cell lines tested displayed an IC50 of < 1.5 mM. In contrast, HS-5 stroma cells and peripheral blood mononuclear cells (PBMCs) did not respond to that MJ concentration, and even at a concentration of 2.5 mM MJ showed a maximal reduction of cell viability of 40%. Similarly to MM cell lines, purified CD138+ primary tumor cells of 3 MM patients displayed an IC50 of < 1.5 mM, suggesting that the differential sensitivity of MM vs. normal cells to MJ is not restricted to cell lines, but is also observed with primary tumor cells. Importantly, neither co-culture with HS-5 stroma nor IL-6 protected MM cells against MJ. Cell death commitment assays revealed that 1h exposure of 1.5 mM MJ induced cell death. Annexin V/PI FACS analysis of MJ-exposed MM cells showed that the cell death is mainly driven by apoptosis, evidenced by cleavage of caspases 3, 8 and 9 as well as of PARP. However, pre-incubation of MM cells with specific caspase inhibitors such as 10 mM of AC-DEVD-CHO, Z-IETD-fmk, Z-LEHD-fmk or 50 mM of Z-VAD only minimally protects the cancer cells from MJ exposure. Therefore, the impact of the MJ is not solely due to caspase triggered proteolytic cascades.

Measurements of cellular ATP content by cell titer glow (CTG; Promega, Madison, WI) assay showed rapid depletion of ATP triggered by MJ action in sensitive MM cell lines. Additionally, we observed that 1 h exposure to 2 mM MJ modulated signaling pathways including IRS1/PI3K/AKT, MEK1/2, as well as Stat3 and JNK. FACS-based cell cycle analysis after propidium iodide staining did not show cell cycle arrest, but rather a rapid transition of cells to G0/G1 No correlation of sensitivity of MM cell lines and the number of mitochondria per cancer cell, as determined by Mitotracker Green (Invitrogen, Carlsbad, CA) -based flow analysis, was observed. We next examined if MJ exhibits either significant antagonism or synergy with established or novel anti-MM agents, including Bortezomib, Lenalidomide, Doxorubicin, Rapamycin or Dexamethasone, but discovered neither. However, MJ displayed synergy when combined with 2-Deoxyglucose. Finally, MJ was tested in vivo in scid/nod mice irradiated with 150 rads, injected with 1× 10⁶ MM1S cells, and then, treated at 500 mg/kg by IP administration on a 5 days on / 2 days off schedule starting two weeks after tumor cell injection, There was an overall survival advantage of MJ-treated animals over the respective controls, with all treated mice (n=10) still alive but 6/10 control mice dead after 27 d.

Based on its rapidity of anti-MM action, favorable safety profile in preclinical models, distinct pattern of molecular sequelae, and compatibility with established anti-MM agents, MJ represents a promising investigational anti-MM agent.

Laubach:Novartis: Consultancy, Honoraria. Richardson:Millennium: (Speakers Bureau up to 7/1/09), Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: (Speakers Bureau up to 7/1/09), Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Anderson:Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Mitsiades:Novartis Pharmaceuticals: Consultancy, Honoraria; Milllennium: Consultancy, Honoraria; Bristol-Myers Squibb : Consultancy, Honoraria; Merck &Co.: Consultancy, Honoraria; Kosan Pharmaceuticals : Consultancy, Honoraria; Pharmion: Consultancy, Honoraria; PharmaMar: Patents & Royalties; Amgen: Research Funding; AVEO Pharma: Research Funding; EMD Serono: Research Funding; Sunesis Pharmaceuticals: Research Funding.