Regional Hyperthermia Enhances Mesenchymal Stem Cell Recruitment to Tumor Stroma: Implications for Mesenchymal Stem Cell-Based Tumor Therapy.

The tropism of mesenchymal stem cells (MSCs) for tumors forms the basis for their use as delivery vehicles for the tumor-specific transport of therapeutic genes, such as the theranostic sodium iodide symporter (NIS). Hyperthermia is used as an adjuvant for various tumor therapies and has been proposed to enhance leukocyte recruitment. Here, we describe the enhanced recruitment of adoptively applied NIS-expressing MSCs to tumors in response to regional hyperthermia. Hyperthermia (41°C, 1 h) of human hepatocellular carcinoma cells (HuH7) led to transiently increased production of immunomodulatory factors. MSCs showed enhanced chemotaxis to supernatants derived from heat-treated cells in a 3D live-cell tracking assay and was validated in vivo in subcutaneous HuH7 mouse xenografts. Cytomegalovirus (CMV)-NIS-MSCs were applied 6-48 h after or 24-48 h before hyperthermia treatment. Using 123I-scintigraphy, thermo-stimulation (41°C, 1 h) 24 h after CMV-NIS-MSC injection resulted in a significantly increased uptake of 123I in heat-treated tumors compared with controls. Immunohistochemical staining and real-time PCR confirmed tumor-selective, temperature-dependent MSC migration. Therapeutic efficacy was significantly enhanced by combining CMV-NIS-MSC-mediated 131I therapy with regional hyperthermia. We demonstrate here for the first time that hyperthermia can significantly boost tumoral MSC recruitment, thereby significantly enhancing therapeutic efficacy of MSC-mediated NIS gene therapy.

Effective control of tumor growth through spatial and temporal control of theranostic sodium iodide symporter (NIS) gene expression using a heat-inducible gene promoter in engineered mesenchymal stem cells.

Purpose: The tumor homing characteristics of mesenchymal stem cells (MSCs) make them attractive vehicles for the tumor-specific delivery of therapeutic agents, such as the sodium iodide symporter (NIS). NIS is a theranostic protein that allows non-invasive monitoring of the in vivo biodistribution of functional NIS expression by radioiodine imaging as well as the therapeutic application of 131I. To gain local and temporal control of transgene expression, and thereby improve tumor selectivity, we engineered MSCs to express the NIS gene under control of a heat-inducible HSP70B promoter (HSP70B-NIS-MSCs). Experimental Design: NIS induction in heat-treated HSP70B-NIS-MSCs was verified by 125I uptake assay, RT-PCR, Western blot and immunofluorescence staining. HSP70B-NIS-MSCs were then injected i.v. into mice carrying subcutaneous hepatocellular carcinoma HuH7 xenografts, and hyperthermia (1 h at 41°C) was locally applied to the tumor. 0 - 72 h later radioiodine uptake was assessed by 123I-scintigraphy. The most effective uptake regime was then selected for 131I therapy. Results: The HSP70B promoter showed low basal activity in vitro and was significantly induced in response to heat. In vivo, the highest tumoral iodine accumulation was seen 12 h after application of hyperthermia. HSP70B-NIS-MSC-mediated 131I therapy combined with hyperthermia resulted in a significantly reduced tumor growth with prolonged survival as compared to control groups. Conclusions: The heat-inducible HSP70B promoter allows hyperthermia-induced spatial and temporal control of MSC-mediated theranostic NIS gene radiotherapy with efficient tumor-selective and temperature-dependent accumulation of radioiodine in heat-treated tumors.

11C-Choline PET/CT in Recurrent Prostate Cancer: Retrospective Analysis in a Large U.S. Patient Series.

Our purpose was to evaluate the performance of 11C-choline PET/CT in detecting biochemically recurrent prostate cancer (PCa) in a large non-European cohort (in the context of emerging evidence for prostate-specific membrane antigen PET in this setting) and to map patterns of PCa recurrence. Methods: We retrospectively analyzed 11C-choline PET/CT scans from 287 patients who were enrolled in an imaging protocol based on rising prostate-specific antigen (PSA) levels (mean, 3.43 ng/mL; median, 0.94 ng/mL; range, 0.15-89.91 ng/mL) and suspected recurrent PCa. A total of 187 patients had undergone primary radical prostatectomy (RP) (79/187 had secondary radiotherapy), 30 had undergone primary radiotherapy, and 70 had a persistent PSA elevation after receiving initial treatment (69 after RP, 1 after radiotherapy). The level of suspicion for recurrence on 11C-choline PET/CT was scored (0, negative; 1, equivocal; 2, positive) by 2 readers. The correlation between 11C-choline PET/CT positivity and initial treatment, Gleason score, National Comprehensive Cancer Network stage, PSA level, PSA doubling time, PSA velocity, and time between initial treatment and PET imaging was evaluated. Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) criteria were used to map 11C-choline recurrence patterns. Results: Considering scores 1 and 2 as positives, consensus between the 2 readers deemed 66% of the 11C-choline PET/CT scans as positive. When sorted by PSA level, 45% of patients with a PSA of less than 0.5 ng/mL, 56% of patients with a PSA of 0.5-0.99 ng/mL, 70% of patients with a PSA of 1.0-1.99 ng/mL, and 90% of patients with a PSA of at least 2.0 ng/mL scored either 1 or 2 on 11C-choline PET/CT scans. When considering scores of 2 only, 11C-choline PET/CT positivity was 54% (28%, 46%, 62%, and 81%, respectively, for patients with PSA < 0.5 ng/mL, 0.5-0.99 ng/mL, 1.0-1.99 ng/mL, and ≥ 2.0 ng/mL). In multivariate analysis, only PSA level was significantly associated with scan positivity. Pattern analysis showed that pelvic lymph nodes were the most common site of recurrence, and 28% of patients had 11C-choline-positive suspected recurrences outside the initial treatment field. Conclusion:11C-choline PET/CT can detect PCa recurrence even among patients with low PSA levels when interpretation accounts for the clinical context, providing a certain pretest probability. Until prostate-specific membrane antigen agents are fully approved for PCa, choline PET/CT may provide clinical utility.

Diffusion-weighted MRI and ADC versus FET-PET and GdT1w-MRI for gross tumor volume (GTV) delineation in re-irradiation of recurrent glioblastoma.

BACKGROUND AND PURPOSE: GTV definition for re-irradiation treatment planning in recurrent glioblastoma (rGBM) is usually based on contrast-enhanced MRI (GdT1w-MRI) and, for an increased specificity, on amino acid PET. Diffusion-weighted (DWI) MRI and ADC maps can reveal regions of high cellularity as surrogate for active tumor. The objective of this study was to compare the localization and quality of diffusion restriction foci (GTV-ADClow) with FET-PET (GTV-PET) and GdT1w-MRI (GTV-GdT1w-MRI). MATERIAL AND METHODS: We prospectively evaluated 41 patients, who received a fractionated stereotactic re-irradiation for rGBM. GTV-PET was generated automatically (tumor-to-background ratio 1.7-1.8) and manually customized. GTV-ADClow was manually defined based on DWI data (3D diffusion gradients, b = 0, 1000 s/mm2) and parametric ADC maps. The localization of recurrence was correlated with initial GdT1w-MRI and PET data. RESULTS: In 30/41 patients, DWI-MRI showed areas with restricted diffusion (mean ADC-value 0.74 ±â€¯0.22 mm2/s). 66% of GTVs-ADClow were located outside the GdT1w-MRI volume and 76% outside increased FET uptake regions. Furthermore, GTVs-ADClow were only partially included in the high dose volume and received in mean 82% of the reference dose. An adjusted volume including GdT1w-MRI, PET-positive and restricted diffusion areas would imply a GTV increase of 48%. GTV-PET and GdT1w-MRI correlated better with the localization of re-recurrence in comparison to GTV-ADClow. CONCLUSION: Unexpectedly, GTV-ADClow overlapped only partially with FET-PET and GdT1w-MRI in rGBM. Moreover, GTV-ADClow correlated poorly with later rGBM-recurrences. Seeing as a restricted diffusion is known to correlate with hypercellularity, this imaging discrepancy could only be further explained in histopathological studies.

Retrospective analysis of 18F-FDG PET/CT for staging asymptomatic breast cancer patients younger than 40 years.

UNLABELLED: National Comprehensive Cancer Network guidelines consider (18)F-FDG PET/CT for only clinical stage III breast cancer patients. However, there is debate whether TNM staging should be the only factor in considering if PET/CT is warranted. Patient age may be an additional consideration, because young breast cancer patients often have more aggressive tumors with potential for earlier metastases. This study assessed PET/CT for staging of asymptomatic breast cancer patients younger than 40 y. METHODS: In this Institutional Review Board-approved retrospective study, our hospital information system was screened for breast cancer patients younger than 40 y who underwent staging PET/CT before any treatment. Patients with symptoms or conventional imaging findings suggestive of distant metastases or with prior malignancy were excluded. Initial stage was based on physical examination, mammography, ultrasound, and breast MR imaging. PET/CT was then evaluated to identify unsuspected extraaxillary regional nodal and distant metastases. RESULTS: One hundred thirty-four patients with initial breast cancer stage I to IIIC met inclusion criteria. PET/CT findings led to upstaging to stage III or IV in 28 patients (21%). Unsuspected extraaxillary regional nodes were found in 15 of 134 patients (11%) and distant metastases in 20 of 134 (15%), with 7 of 134 (5%) demonstrating both. PET/CT revealed stage IV disease in 1 of 20 (5%) patients with initial clinical stage I, 2 of 44 (5%) stage IIA, 8 of 47 (17%) stage IIB, 4 of 13 (31%) stage IIIA, 4 of 8 (50%) stage IIIB, and 1 of 2 (50%) stage IIIC. All 20 patients upstaged to stage IV were histologically confirmed. Four synchronous thyroid and 1 rectal malignancies were identified. CONCLUSION: PET/CT revealed distant metastases in 17% of asymptomatic stage IIB breast cancer patients younger than 40 y. Although guidelines of the National Comprehensive Cancer Network recommend against systemic staging in patients with stage II disease, our data suggest that PET/CT might be valuable in younger patients with stage IIB and III disease. Use of PET/CT in younger patients has the potential to reduce the morbidity and cost of unnecessary therapies in young breast cancer patients.

Targeted radiotherapy of prostate cancer with a gastrin-releasing peptide receptor antagonist is effective as monotherapy and in combination with rapamycin.

UNLABELLED: The gastrin-releasing peptide receptor (GRPr) is overexpressed in prostate cancer and is an attractive target for radionuclide therapy. In addition, inhibition of the protein kinase mammalian target of rapamycin (mTOR) has been shown to sensitize various cancer cells to the effects of radiotherapy. METHODS: To determine the effect of treatment with rapamycin and radiotherapy with a novel (177)Lu-labeled GRPr antagonist ((177)Lu-RM2, BAY 1017858) alone and in combination, in vitro and in vivo studies were performed using the human PC-3 prostate cancer cell line. PC-3 cell proliferation and (177)Lu-RM2 uptake after treatment with rapamycin were assessed in vitro. To determine the influence of rapamycin on (177)Lu-RM2 tumor uptake, in vivo small-animal PET studies with (68)Ga-RM2 were performed after treatment with rapamycin. To study the efficacy of (177)Lu-RM2 in vivo, mice with subcutaneous PC-3 tumors were treated with (177)Lu-RM2 alone or after pretreatment with rapamycin. RESULTS: Stable expression of GRPr was maintained after rapamycin treatment with doses up to 4 mg/kg in vivo. Monotherapy with (177)Lu-RM2 at higher doses (72 and 144 MBq) was effective in inducing complete tumor remission in 60% of treated mice. Treatment with 37 MBq of (177)Lu-RM2 and rapamycin in combination led to significantly longer survival than with either agent alone. No treatment-related toxicity was observed. CONCLUSION: Radiotherapy using a (177)Lu-labeled GRPr antagonist alone or in combination with rapamycin was efficacious in inhibiting in vivo tumor growth and may be a promising strategy for treatment of prostate cancer.