Intracarotid recombinant human tumor necrosis factor-alpha reduces cerebral blood flow and methionine uptake in rat brain tumors

Reduced [14C]-methionine uptake and fecundity in Schistosoma mansoni females treated with recombinant tumor necrosis factor α in vitro

Recombinant human TNFα (rhTNFα) has previously been shown to reduce fecundity in Schistosoma mansoni adult females maintained in vitro without males, and adversely affect the uptake of [14C]-tyrosine, an amino acid required for schistosome vitellogenesis. Here we report on the effect of rhTNFα on [14C]-methionine uptake in both separated and paired females, and the effect of three different preparations of rTNFα on schistosome oviposition in vitro. In the absence of rhTNFa, separated females incorporated only 30% of the [14C]-methionine incorporated by paired females in a dose and time-dependent manner, suggesting low metabolic activity of females in the absence of males. Separated females and worm-pairs were treated with increasing doses of rhTNFα for 2 or 4 hr and then incubated in RPMI 1640 containing 10% fetal calf serum (FCS) and 5 µCi ml-1[14C]-methionine for 1 hr. Separated females treated with rhTNFa for 4 hr incorporated less methionine than those treated for 2 hr. In contrast, paired females treated with rhTNFa incorporated significantly smaller amounts of [14C]-methionine in a TNFa dose-dependent but time-independent manner [2 hr (P = 0.001) or 4 hr (P = 0.027) One-Way ANOVA]. Worm-pairs maintained in RPMI 1640 containing 10% FCS and 100 ng ml-1 of any of the three rTNFa preparations laid significantly fewer eggs than the worms cultured without rTNFα(P = 0.001; Kruskal-Wallis Test). We also observed that among rTNFα-treated worm-pairs, females were sluggish and tended to separate from their male partners. These observations suggest that TNFa inhibits [14C]-methionine uptake and reduces fecundity in females paired with males. Since paired females incorporate substantially greater amounts of [14C]-methionine, the role of males in stimulating metabolic activity in females is affirmed. Reduced amino acid uptake, and possibly other nutrients, may contribute to the diminished fecundity observed in TNFa-treated females.

Amino acid PET tracers are reliable markers of treatment responses to single-agent or combination therapies including temozolomide, interferon-β, and/or bevacizumab for glioblastoma

INTRODUCTION

We examined whether the amino acid PET tracers, trans-1-amino-3-(18)F-fluorocyclobutanecarboxylic acid (anti-(18)F-FACBC) and (11)C-methyl-l-methionine ((11)C-Met), are suitable for detecting early responses to combination therapies including temozolomide (TMZ), interferon-β (IFN), and bevacizumab (Bev) in glioblastoma.

METHODS

Human glioblastoma U87MG (U87) cells were incubated with low dose TMZ to induce chemoresistance. Both trans-1-amino-3-fluoro-1-(14)C-cyclobutanecarboxylic acid (anti-(14)C-FACBC) and (3)H-methyl-l-methionine ((3)H-Met) uptake were quantified using triple-label accumulation assays to examine the relationship between tracer uptake and proliferation ((3)H-thymidine (TdR) accumulation) in vitro. U87 and U87R (TMZ-resistant subculture) cells were inoculated into the right and left basal ganglia, respectively, of F344/N-rnu rats. The efficacy of single-agent (TMZ, Bev) and combination therapy (TMZ/IFN, TMZ/Bev, TMZ/IFN/Bev) was examined in orthotopic gliomas using MRI, Evans blue extravasation, anti-(14)C-FACBC, and (3)H-Met autoradiography, and MIB-1 immunostaining.

RESULTS

TMZ treatment decreased (3)H-TdR accumulation and the volume distribution of anti-(14)C-FACBC and (3)H-Met in U87 but not U87R cells. TMZ/IFN combination therapy significantly decreased these parameters in U87R cells; however, Bev had no additional effect in vitro. In vivo, U87R-derived gliomas were observed as equivocal tumors on MRI and T2-high intensity lesions. Bev treatment, either alone or in combination, markedly decreased U87 enhancing lesions. By contrast, autoradiographic images using anti-(14)C-FACBC and (3)H-Met clearly delineated tumor extent, which spread widely beyond T2-high intensity lesions and enhancing lesions. TMZ therapy significantly decreased tracer accumulation and proliferation of U87- but not U87R-derived tumors. TMZ/IFN combination treatment significantly decreased these parameters in U87R tumors, which were further reduced (in both tumor types) by Bev addition. Tracer uptake correlated with the MIB-1 proliferation index. However, MRI was unsuitable for tumor delineation and assessment of Bev treatment response.

CONCLUSIONS

Triple-agent therapy (TMZ/IFN/Bev) was effective against even TMZ-resistant glioblastomas. PET with amino acid tracers provides useful information on the early response of glioblastomas to single-agent and combination therapy.

Trans-1-amino-3-18F-fluorocyclobutanecarboxylic acid (anti-18F-FACBC) is a feasible alternative to 11C-methyl-L-methionine and magnetic resonance imaging for monitoring treatment response in gliomas

INTRODUCTION

Amino acid PET tracers are promising for visualizing gliomas and evaluating radiochemotherapeutic effects. We compared the glioma detection and early response assessment utility between trans-1-amino-3-fluoro-1-(14)C-cyclobutanecarboxylic acid (anti-(14)C-FACBC) and (3)H-methyl-l-methionine ((3)H-Met) by simultaneously analyzing their uptake by rat gliomas treated with and without temozolomide (TMZ) in vitro and in vivo.

METHODS

C6 rat gliomas were incubated with low-dose TMZ to induce chemoresistance. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated a significantly greater surviving fraction in the TMZ-resistant subline (C6R) than in drug-naive cells (C6). The anti-(14)C-FACBC and (3)H-Met uptakes were quantified using a triple-label accumulation assay to examine the relationship between tracer uptake and proliferation ((3)H-thymidine (TdR) accumulation rate) in tumor cells. C6 and C6R cells were inoculated into the right and left basal ganglia, respectively, of rats. Efficacy of TMZ against the orthotopic gliomas was analyzed by MRI, Evans blue extravasation, anti-(14)C-FACBC and (3)H-Met autoradiography, and MIB-5 proliferation index.

RESULTS

The (3)H-TdR accumulation rate and amino acid tracer (anti-(14)C-FACBC and (3)H-Met) uptake significantly decreased 48 and 72 h, respectively, after TMZ treatment in C6 but not C6R cells. Anti-(14)C-FACBC uptake correlated significantly with (3)H-Met uptake and the (3)H-TdR accumulation rate. In the intracerebral glioma model, anti-(14)C-FACBC and (3)H-Met autoradiography clearly delineated the tumor extent, which spread well beyond the high-T2-intensity and enhancing lesions visible on MRI and Evans blue extravasation. TMZ significantly decreased anti-(14)C-FACBC and (3)H-Met uptake and the MIB-5 index of C6 but not C6R tumors. TMZ inhibited tracer uptake and tumor proliferation before morphological changes on MRI.

CONCLUSIONS

Anti-(14)C-FACBC, like (3)H-Met, was more sensitive than post-contrast T1-weighted MRI for detecting tumor extent and early tumor response to TMZ treatment. Anti-(18)F-FACBC should be a sensitive and precise imaging biomarker for tumor extent visualization and response assessment in glioma patients.

(99m)Tc-MIBI imaging for prediction of therapeutic effects of second-generation MDR1 inhibitors in malignant brain tumors

The aim of this study was to explore whether (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) is suitable to elucidate multidrug resistance and prediction of potentiation of antitumor agents by second-generation MDR1 inhibitors (PSC833, MS-209) in malignant brain tumors in rat. Malignant tumor cells (RG2 and C6 gliomas, Walker 256 carcinoma) were incubated with low dose vincristine (VCR) to induce multidrug resistance. MTT assay demonstrated a significant increase of surviving fractions in VCR-resistant sublines compared to those of drug-naive cells. Reverse transcriptase polymerase chain reaction revealed higher expression of MDR1 mRNA in VCR-resistant cells than drug-naive cells in each line. Volume distribution (V(d)) of (99m)Tc-MIBI was negatively correlated with MDR1 mRNA expression among drug-naive and VCR-resistant cells. MDR1 inhibitors decreased surviving fractions and increased V(d) of (99m)Tc-MIBI significantly in VCR-resistant sublines, whereas MDR1 mRNA expression was unchanged. These findings indicate that (99m)Tc-MIBI efflux was functionally suppressed by MDR1 inhibitors. Autoradiographic images of (99m)Tc-MIBI revealed higher uptake in drug-naive cells at basal ganglia compared with VCR-resistant cells at the opposite basal ganglia of rats. Oral administration of the second-generation MDR1 inhibitors significantly increased (99m)Tc-MIBI accumulation of both tumors. Therapeutic effects of VCR with or without the MDR1 inhibitors were also evaluated autoradiographically using (14)C-methyl-L-methionine ((14)C-Met) and MIB-5 index. (14)C-Met uptake and MIB-5 index of both tumors treated with VCR following the MDR1 inhibitor treatment significantly decreased compared with tumors treated with VCR alone. Analysis of (99m)Tc-MIBI accumulation is considered informative for detecting MDR1-mediated drug resistance and for monitoring the therapeutic effects of MDR1 inhibitors in malignant brain tumors.