The Hormone KL1: A Regulator of Breast Cancer Cell Metabolism.

BACKGROUND: Klotho is a transmembrane protein that can be shed and can act as a circulating hormone in three forms: soluble klotho (KL1 + KL2), KL1, and KL2. Klotho was discovered as a gene implicated in aging through inhibition of the IGF-I pathway. Our laboratory discovered the role of klotho as a tumor suppressor in breast cancer and other malignancies. Furthermore, we showed that the KL1 domain mediates this activity. Altered cancer cell metabolism is a hallmark of cancer and our lab demonstrated various effects of klotho on breast cancer cell metabolism. Thus, klotho inhibited glycolysis and activated adenosine monophosphate activating kinase (AMPK), an energy sensor pathway. Moreover, inhibition of AMPK reduced the tumor suppressor activity of klotho. OBJECTIVES: To assess the effect of KL1 on breast tumor cells metabolism, as KL1 possesses the tumor suppressor activity of klotho. METHODS: We used MCF-7 breast cancer cells treated with soluble or over-expressed KL1 and klotho. Glycolysis was assessed by measuring mRNA levels of key glycolytic enzymes using reverse transcription polymerase chain reaction and by measuring lactate and glucose levels in media. The AMPK pathway was studied by monitoring AMPK phosphorylation as well as its down-stream target, acetyl-CoA carboxylase, using western blotting. Wound healing assay was used to assess cell migration. RESULTS: KL1 treatment reduced glycolytic enzymes mRNA levels and the activity of hexokinase, similar to klotho treatment. Furthermore, KL1 reduced glucose uptake and decreased lactate production. KL1 elevated phosphorylated acetyl-CoA carboxylase and phosphorylated AMPK levels. Inhibition AMPK (using a mutant AMPK activator) stopped KL1 from inhibiting cell migration, suggesting AMPK underlies klotho's tumor suppressor activity. CONCLUSIONS: Our data indicate KL1 as a regulator of metabolic activity in breast cancer and suggest that metabolic alterations underlie KL1 tumor suppressor activities. Furthermore, as KL1 and klotho share a similar effect on cell metabolism, our results further support the central role KL1 domain plays in klotho's tumor suppressor activity.

Endoneurial macrophages induce perineural invasion of pancreatic cancer cells by secretion of GDNF and activation of RET tyrosine kinase receptor.

Perineural invasion of cancer cells (CPNI) is found in most patients with pancreatic adenocarcinomas (PDA), prostate, or head and neck cancers. These patients undergo palliative rather than curative treatment due to dissemination of cancer along nerves, well beyond the extent of any local invasion. Although CPNI is a common source of distant tumor spread and a cause of significant morbidity, its exact mechanism is undefined. Immunohistochemical analysis of specimens excised from patients with PDAs showed a significant increase in the number of endoneurial macrophages (EMΦ) that lie around nerves invaded by cancer compared with normal nerves. Video microscopy and time-lapse analysis revealed that EMΦs are recruited by the tumor cells in response to colony-stimulated factor-1 secreted by invading cancer cells. Conditioned medium (CM) of tumor-activated EMΦs (tEMΦ) induced a 5-fold increase in migration of PDA cells compared with controls. Compared with resting EMΦs, tEMΦs secreted higher levels of glial-derived neurotrophic factor (GDNF), inducing phosphorylation of RET and downstream activation of extracellular signal-regulated kinases (ERK) in PDA cells. Genetic and pharmacologic inhibition of the GDNF receptors GFRA1 and RET abrogated the migratory effect of EMΦ-CM and reduced ERK phosphorylation. In an in vivo CPNI model, CCR2-deficient mice that have reduced macrophage recruitment and activation showed minimal nerve invasion, whereas wild-type mice developed complete sciatic nerve paralysis due to massive CPNI. Taken together, our results identify a paracrine response between EMΦs and PDA cells that orchestrates the formation of cancer nerve invasion.

Synergistic antileukemic activity of carnosic acid-rich rosemary extract and the 19-nor Gemini vitamin D analogue in a mouse model of systemic acute myeloid leukemia.

OBJECTIVE: Differentiation therapy with the hormonal form of vitamin D, 1alpha,25-dihydroxyvitamin D(3) (1,25D(3)), is a promising approach to treatment of acute myeloid leukemia (AML); however, 1,25D(3) induces hypercalcemia at pharmacologically active doses. We investigated the in vitro and in vivoantileukemic efficacy of combined treatment with non-toxic doses of a low-calcemic 1,25D(3) analogue, 1,25-dihydroxy-21(3-hydroxy-3-methyl-butyl)-19-nor-cholecalciferol (19-nor-Gemini; Ro27-5646), and rosemary plant agents in a mouse model of AML. METHODS: Proliferation and differentiation of WEHI-3B D- (WEHI) murine myelomonocytic leukemia cellsin vitro were determined by standard assays. Reactive oxygen species, glutathione and protein expression levels were measured by flow cytometry, enzymatic assay and Western blotting, respectively. Systemic AML was developed by intravenous injection of WEHI cells in syngeneic Balb/c mice. RESULTS: 19-nor-Gemini had a higher potency than its parent compounds, Gemini (Ro27-2310) and 1,25D(3), in the induction of differentiation (EC(50) = 0.059 +/- 0.011, 0.275 +/- 0.093 and 0.652 +/- 0.085 nM, respectively) and growth arrest (IC(50) = 0.072 +/- 0.018, 0.165 +/- 0.061 and 0.895 +/- 0.144 nM, respectively) in WEHI cells in vitro, and lower in vivo toxicity. Combined treatment of leukemia-bearing mice with 19-nor-Gemini (injected intraperitoneally) and standardized rosemary extract (mixed with food) resulted in a synergistic increase in survival (from 42.2 +/- 2.5 days in untreated mice to 66.5 +/- 4.2 days, n = 3) and normalization of white blood cell and differential counts. This was consistent with strong cooperative antiproliferative and differentiation effects of low concentrations of 19-nor-Gemini or 1,25D(3) combined with rosemary extract or its major polyphenolic component, carnosic acid, as well as with the antioxidant action of rosemary agents and vitamin D derivatives in WEHI cell cultures. CONCLUSION: Combined effectiveness of 1,25D(3) analogues and rosemary agents against mouse AML warrants further exploration of this therapeutic approach in translational models of human leukemia.