Liver metastasis from colorectal cancer is a leading cause of cancer mortality. Myeloid cells play pivotal roles in the metastatic process, but their prometastatic functions in liver metastasis ...remain incompletely understood. To investigate their role, we simulated liver metastasis in C57BL/6 mice through intrasplenic inoculation of MC38 colon carcinoma cells. Among the heterogeneous myeloid infiltrate, we identified a distinct population of CD11b/Gr1mid cells different from other myeloid populations previously associated with liver metastasis. These cells increased in number dramatically during establishment of liver metastases and were recruited from bone marrow by tumor‐derived CCL2. Liver metastasis of Lewis lung carcinoma cells followed this pattern but this mechanism is not universal as liver colonization by B16F1 melanoma cells did not recruit similar subsets. Inhibition of CCL2 signaling and absence of its cognate receptor CCR2 reduced CD11b/Gr1mid recruitment and decreased tumor burden. Depletion of the CD11b/Gr1mid subset in a transgenic CD11b‐diphtheria toxin receptor mouse model markedly reduced tumor cell proliferation. There was no evidence for involvement of an adaptive immune response in the prometastatic effects of CD11b/Gr1mid cells. Additionally, an analogous myeloid subset was found in liver metastases of some colorectal cancer patients. Conclusion: Collectively, our findings highlight the importance of myeloid cells—in this case a selective CD11b/Gr1mid subset—in sustaining development of colorectal cancer liver metastasis and identify a potential target for antimetastatic therapy. (HEPATOLOGY 2013)
Myeloid cells are known to mediate metastatic progression. Here, we attempted to elucidate the mechanisms underlying these effects by identifying gene expression alterations in cancer cells forming ...hepatic metastases after myeloid cell depletion. Hepatic metastases are heavily infiltrated by CD11b+ myeloid cells. We established hepatic metastases in transgenic CD11b‐diphtheria toxin receptor mice by intrasplenic injection of MC38 colon and Lewis lung carcinoma cells before depleting myeloid cells with diphtheria toxin. Myeloid cell depletion inhibited metastatic growth with a marked diminishment of tumor vasculature. Expression of ANGPTL7 (angiopoietin‐like 7), a protein not previously linked to metastasis, was highly up‐regulated in cancer cells after myeloid cell depletion. This effect was duplicated in tissue culture, where coculture of cancer cells with tumor‐conditioned myeloid cells from liver metastases or myeloid cell conditioned media down‐regulated ANGPTL7 expression. Analogous to myeloid cell depletion, overexpression of ANGPTL7 in cancer cells significantly reduced hepatic metastasis formation and angiogenesis. We found that ANGPTL7 itself has strong antiangiogenic effects in vitro. Furthermore, analysis of The Cancer Genome Atlas colorectal and breast cancer data sets revealed striking ANGPTL7 underexpression in cancerous compared to normal tissues. Also, ANGPTL7 was down‐regulated in metastatic liver colonies of colorectal cancer patients compared to their adjacent liver tissue. Conclusion: Myeloid cells promote liver metastasis by down‐regulating ANGPTL7 expression in cancer cells; our findings implicate ANGPTL7 as a mediator of metastatic progression and a potential target for interference with liver metastases. (Hepatology 2015;62:521–533
Brain metastasis is a common complication of cancer patients and is associated with poor survival. Histological data from patients with brain metastases suggest that microglia are the major immune ...population activated around the metastatic foci. Microglia and macrophages have the ability to polarize to different phenotypes and to exert both tumorigenic and cytotoxic effects. However, the role of microglia/macrophages during the early stages of metastatic growth in the brain has not yet been determined. The aim of this study was to profile microglial/macrophage activation in a mouse model of breast cancer brain metastasis during the early stages of tumor growth, and to assess the role of the anti-inflammatory microglial/macrophage population, specifically, during this phase. Following intracerebral injection of 5 × 10
4T1-GFP mammary carcinoma cells into female BALB/c mice, robust microglial/macrophage activation around the 4T1 metastatic foci was evident throughout the time-course studied (28 days) and correlated positively with tumor volume (
= 0.67). Populations of classically (proinflammatory) and alternatively (anti-inflammatory) activated microglia/macrophages were identified immunohistochemically by expression of either induced nitric oxide synthase/cyclooxygenase 2 or mannose receptor 1/arginase 1, respectively. Temporally, levels of both pro- and anti-inflammatory cells were broadly stable across the time-course. Subsequently, selective depletion of the anti-inflammatory microglia/macrophage population by intracerebral injection of mannosylated clodronate liposomes significantly reduced metastatic tumor burden (
< 0.01). Moreover, increased levels of apoptosis were associated with tumors in clodronate liposome treated animals compared to controls (
< 0.05). These findings suggest that microglia/macrophages are important effectors of the inflammatory response in the early stages of brain metastasis, and that targeting the anti-inflammatory microglial/macrophage population may offer an effective new therapeutic avenue for patients with brain metastases.
Current strategies for early detection of breast and other cancers are limited in part because some lesions identified as potentially malignant do not develop into aggressive tumors. Acid pH has been ...suggested as a key characteristic of aggressive tumors that might distinguish aggressive lesions from more indolent pathology. We therefore investigated the novel class of molecules, pH low insertion peptides (pHLIPs), as markers of low pH in tumor allografts and of malignant lesions in a mouse model of spontaneous breast cancer, BALB/neu-T. pHLIP Variant 3 (Var3) conjugated with fluorescent Alexa546 was shown to insert into tumor spheroids in a sequence-specific manner. Its signal reflected pH in murine tumors. It was induced by carbonic anhydrase IX (CAIX) overexpression and inhibited by acetazolamide (AZA) administration. By using31P magnetic resonance spectroscopy (MRS), we demonstrated that pHLIP Var3 was retained in tumors of pH equal to or less than 6.7 but not in tissues of higher pH. In BALB/neu-T mice at different stages of the disease, the fluorescent signal from pHLIP Var3 marked cancerous lesions with a very low false-positive rate. However, only ∼60% of the smallest lesions retained a pHLIP Var3 signal, suggesting heterogeneity in pH. Taken together, these results show that pHLIP can identify regions of lower pH, allowing for its development as a theranostic tool for clinical applications.
Nanomedicines allow active targeting of cancer for diagnostic and therapeutic applications through incorporation of multiple functional components. Frequently, however, clinical translation is ...hindered by poor intratumoural delivery and distribution. The application of physical stimuli to promote tumour uptake is a viable route to overcome this limitation. In this study, ultrasound-mediated cavitation of microbubbles was investigated as a mean of enhancing the delivery of a liposome designed for chemo-radionuclide therapy targeted to EGFR overexpressing cancer.
Liposomes (
In-EGF-LP-Dox) were prepared by encapsulation of doxorubicin (Dox) and surface functionalisation with Indium-111 tagged epidermal growth factor. Human breast cancer cell lines with high and low EGFR expression (MDA-MB-468 and MCF7 respectively) were used to study selectivity of liposomal uptake, subcellular localisation of drug payload, cytotoxicity and DNA damage. Liposome extravasation following ultrasound-induced cavitation of microbubbles (SonoVue®) was studied using a tissue-mimicking phantom.
stability, pharmacokinetic profile and biodistribution were evaluated following intravenous administration of
In-labelled, EGF-functionalised liposomes to mice bearing subcutaneous MDA-MB-468 xenografts. Finally, the influence of ultrasound-mediated cavitation on the delivery of liposomes into tumours was studied.
Liposomes were loaded efficiently with Dox, surface decorated with
In-EGF and showed selective uptake in MDA-MB-468 cells compared to MCF7. Following binding to EGFR, Dox was released into the intracellular space and
In-EGF shuttled to the cell nucleus
DNA damage and cell kill were higher in MDA-MB-468 than MCF7 cells. Moreover, Dox and
In were shown to have an additive cytotoxic effect in MDA-MB-468 cells. US-mediated cavitation increased the extravasation of liposomes in an
gel phantom model.
, the application of ultrasound with microbubbles increased tumour uptake by 66% (p<0.05) despite poor vascularisation of MDA-MB-468 xenografts (as shown by DCE-MRI).
In-EGF-LP-Dox designed for concurrent chemo-radionuclide therapy showed specificity for and cytotoxicity towards EGFR-overexpressing cancer cells. Delivery to tumours was enhanced by the use of ultrasound-mediated cavitation indicating that this approach has the potential to deliver cytotoxic levels of therapeutic radionuclide to solid tumours.
There is a need to improve the treatment of prostate cancer (PCa) and reduce treatment side effects. Vascular-targeted photodynamic therapy (VTP) is a focal therapy for low-risk low-volume localised ...PCa, which rapidly disrupts targeted tumour vessels. There is interest in expanding the use of VTP to higher-risk disease. Tumour vasculature is characterised by vessel immaturity, increased permeability, aberrant branching and inefficient flow. FRT alters the tumour microenvironment and promotes transient 'vascular normalisation'. We hypothesised that multimodality therapy combining fractionated radiotherapy (FRT) and VTP could improve PCa tumour control compared against monotherapy with FRT or VTP.
We investigated whether sequential delivery of FRT followed by VTP 7 days later improves flank TRAMP-C1 PCa tumour allograft control compared to monotherapy with FRT or VTP.
FRT induced 'vascular normalisation' changes in PCa flank tumour allografts, improving vascular function as demonstrated using dynamic contrast-enhanced magnetic resonance imaging. FRT followed by VTP significantly delayed tumour growth in flank PCa allograft pre-clinical models, compared with monotherapy with FRT or VTP, and improved overall survival.
Combining FRT and VTP may be a promising multimodal approach in PCa therapy. This provides proof-of-concept for this multimodality treatment to inform early phase clinical trials.
Neuroblastoma has one of the lowest survival rates of all childhood cancers, despite the use of intensive treatment regimens. Preclinical models of neuroblastoma are essential for testing new ...multimodality protocols, including those that involve radiotherapy (RT). The aim of this study was to develop a robust method for RT planning and tumour response monitoring based on combined MRI and cone-beam CT (CBCT) imaging and to apply it to a widely studied mouse xenograft model of neuroblastoma, SK-N-SH.
As part of a tumour growth inhibition study, SK-N-SH xenografts were generated in BALB/c nu/nu mice. Mice (n = 8) were placed in a printed MR- and CT-compatible plastic cradle, imaged using a 4.7-T MRI scanner and then transferred to a small animal radiation research platform (SARRP) irradiator with on-board CBCT. MRI/CBCT co-registration was performed to enable RT planning using the soft-tissue contrast afforded by MRI prior to delivery of RT (5 Gy). Tumour response was assessed by serial MRI and calliper measurements.
SK-N-SH xenografts formed soft, deformable tumours that could not be differentiated from surrounding normal tissues using CBCT. MR images, which allowed clear delineation of tumours, were successfully co-registered with CBCT images, allowing conformal RT to be delivered. MRI measurements of tumour volume 4 days after RT correlated strongly with length of survival time.
MRI allowed precision RT of SK-N-SH tumours and provided an accurate means of measuring tumour response. Advances in knowledge: MRI-based RT planning of murine tumours is feasible using an SARRP irradiator.
To assess the efficacy of different schedules for combining external beam radiotherapy (EBRT) with molecular radiotherapy (MRT) using
I-mIBG in the management of neuroblastoma.
BALB/c nu/nu mice ...bearing SK-N-SH neuroblastoma xenografts were assigned to five treatment groups:
I-mIBG 24h after EBRT, EBRT 6days after
I-mIBG, EBRT alone,
I-mIBG alone and control (untreated). A total of 56 mice were assigned to 3 studies. Study 1: Vessel permeability was evaluated using dynamic contrast-enhanced (DCE)-MRI (n=3). Study 2: Tumour uptake of
I-mIBG in excised lesions was evaluated by γ-counting and autoradiography (n=28). Study 3: Tumour volume was assessed by longitudinal MR imaging and survival was analysed (n=25). Tumour dosimetry was performed using Monte Carlo simulations of absorbed fractions with the radiation transport code PENELOPE.
Given alone, both
I-mIBG and EBRT resulted in a seven-day delay in tumour regrowth. Following EBRT, vessel permeability was evaluated by DCE-MRI and showed an increase at 24h post irradiation that correlated with an increase in
I-mIBG tumour uptake, absorbed dose and overall survival in the case of combined treatment. Similarly, EBRT administered seven days after MRT to coincide with tumour regrowth, significantly decreased the tumour volume and increased overall survival.
This study demonstrates that combining EBRT and MRT has an enhanced therapeutic effect and emphasizes the importance of treatment scheduling according to pathophysiological criteria such as tumour vessel permeability and tumour growth kinetics.
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