Hematopoietic stem and progenitor cell migration after hypofractionated radiation therapy in a murine model

Obesity Promotes Marrow-Derived Myeloid Cell Accumulation While Exercise Reduces Proliferative Signaling in Colon Cancer

PURPOSE

Obesity increases colon cancer risk that has been previously linked to marrow-derived myeloid cells. We previously demonstrated that exercise training (EX) prevents colon cancer initiation, potentially through reduced myelopoiesis. However, it remains unknown whether early myeloid cell accumulation and inflammation in the colon precedes carcinogenesis with high-fat diet (HFD)-induced obesity, and if EX can attenuate these effects. We hypothesized that obesity would promote colon carcinogenesis that was preceded by myeloid cell accumulation and inflammation that would be attenuated by EX.

METHODS

C57BL/6 mice were randomized to a HFD or control (CON) diet for 8 weeks. The HFD mice switched to CON diet and all mice were given intraperitoneal injections of azoxymethane (AOM) to induce colon cancer and randomized into EX or sedentary (SED) conditions.

RESULTS

HFD mice developed more aberrant crypt foci (ACF), a marker for early carcinogenesis, compared with CON ( P < 0.01), and EX developed fewer ACF compared with SED ( P < 0.0001). Marrow-derived ( P < 0.001) CD206 + macrophages were elevated in HFD compared with CON at study week 16 ( P < 0.01). Marrow-derived CD206 - macrophages ( P < 0.05) and marrow-derived ( P < 0.05) CD206 + macrophages were more abundant in HFD compared with CON at study week 42. EX did not alter colon immune cell populations. β-catenin protein was higher in HFD compared with CON at study week 42 ( P < 0.05), and STAT3 protein content was lower at study week 28 with EX compared with SED ( P < 0.05).

CONCLUSIONS

The results suggest that obesity promotes colon ACF formation, potentially through early inflammatory myeloid cell accumulation. Despite attenuating ACF, EX did not alter myeloid cell accumulation in the colon, suggesting that EX inhibits ACF formation through alternative mechanisms which may include reduced β-catenin and STAT3 signaling.

Intratumoural haematopoietic stem and progenitor cell differentiation into M2 macrophages facilitates the regrowth of solid tumours after radiation therapy

BACKGROUND

Bone-marrow-derived haematopoietic stem and progenitor cells (HSPCs) are a prominent part of the highly complex tumour microenvironment (TME) where they localise within tumours and maintain haematopoietic potency. Understanding the role HSPCs play in tumour growth and response to radiation therapy (RT) may lead to improved patient treatments and outcomes.

METHODS

We used a mouse model of non-small cell lung carcinoma where tumours were exposed to RT regimens alone or in combination with GW2580, a pharmacological inhibitor of colony stimulating factor (CSF)-1 receptor. RT-PCR, western blotting and immunohistochemistry were used to quantify expression levels of factors that affect HSPC differentiation. DsRed+ HSPC intratumoural activity was tracked using flow cytometry and confocal microscopy.

RESULTS

We demonstrated that CSF-1 is enhanced in the TME following exposure to RT. CSF-1 signaling induced intratumoural HSPC differentiation into M2 polarised tumour-associated macrophages (TAMs), aiding in post-RT tumour survival and regrowth. In contrast, hyperfractionated/pulsed radiation therapy (PRT) and GW2580 ablated this process resulting in improved tumour killing and mouse survival.

CONCLUSIONS

Tumours coopt intratumoural HSPC fate determination via CSF-1 signaling to overcome the effects of RT. Thus, limiting intratumoural HSPC activity represents an attractive strategy for improving the clinical treatment of solid tumours.

MiRNA-142-3p increases radiosensitivity in human umbilical cord blood mononuclear cells by inhibiting the expression of CD133

This study is to explore the molecular regulation mechanism of CD133 which is associated with malignancy and poor prognosis of blood system diseases. CD133+HUCB-MNC (human umbilical cord blood mononuclear cells) and CD133-HUCB-MNC were isolated and amplificated from umbilical cord blood, and then were exposed to different doses of radiation and subjected to a clonogenic assay. CCK-8 kit was used to detect cell viability, Annexin V-FITC/PI cell apoptosis detection kit was used for the detection of apoptotic cells and the BrdU assay was performed by flow cytometry. The expression of protein was analyzed by western blots. The profile of miRNA expression in response to radiation was examined and validated by RT-PCR. miR-142-3p inhibited the expression of CD133 in umbilical cord blood mononuclear cells to increase radiosensitivity. CD133+HUCB-MNC cells were more radioresistant compared with CD133-HUCB-MNC cells. CD133+HUCB-MNC cells showed higher p-AKT and p-ERK levels after radiation. And miR-142-3p acted on 3'UTR of CD133 mRNA to inhibit CD133 expression. Moreover, miRNA-142-3p mimic increased radiosensitivity in CD133+HUCB-MNC cells. Our results elucidated a novel regulation pathway in hematopoietic stem cells and suggested a potential therapeutic approach for blood system diseases therapy.

Validating the pivotal role of the immune system in low-dose radiation-induced tumor inhibition in Lewis lung cancer-bearing mice

Although low-dose radiation (LDR) possesses the two distinct functions of inducing hormesis and adaptive responses, which result in immune enhancement and tumor inhibition, its clinical applications have not yet been elucidated. The major obstacle that hinders the application of LDR in the clinical setting is that the mechanisms underlying induction of tumor inhibition are unclear, and the risks associated with LDR are still unknown. Thus, to overcome this obstacle and elucidate the mechanisms mediating the antitumor effects of LDR, in this study, we established an in vivo lung cancer model to investigate the participation of the immune system in LDR-induced tumor inhibition and validated the pivotal role of the immune system by impairing immunity with high-dose radiation (HDR) of 1 Gy. Additionally, the LDR-induced adaptive response of the immune system was also observed by sequential HDR treatment in this mouse model. We found that LDR-activated T cells and natural killer cells and increased the cytotoxicity of splenocytes and the infiltration of T cells in the tumor tissues. In contrast, when immune function was impaired by HDR pretreatment, LDR could not induce tumor inhibition. However, when LDR was administered before HDR, the immunity could be protected from impairment, and tumor growth could be inhibited to some extent, indicating the induction of the immune adaptive response by LDR. Therefore, we demonstrated that immune enhancement played a key role in LDR-induced tumor inhibition. These findings emphasized the importance of the immune response in tumor radiotherapy and may help promote the application of LDR as a novel approach in clinical practice.

Bone Marrow Cell Trafficking Analyzed by 89Zr-oxine Positron Emission Tomography in a Murine Transplantation Model

Purpose: The success of hematopoietic stem cell transplantation (HSCT) depends on donor cell homing to the bone marrow. However, there is no reliable method of noninvasively monitoring the kinetics and distribution of transferred cells. Using zirconium-89 (89Zr)-oxine cell labeling combined with PET imaging, we sought to visualize and quantify donor cell homing in a mouse bone marrow transplantation model.Experimental Design: The effect of 89Zr-oxine labeling on bone marrow cell viability and differentiation was evaluated in vitro89Zr-labeled bone marrow cells (2 × 107 cells, 16.6 kBq/106 cells) were transferred intravenously, and serial microPET images were obtained (n = 5). The effect of a CXCR4 inhibitor, plerixafor (5 mg/kg) and G-CSF (2.5 μg) on bone marrow homing and mobilization were examined (n = 4). Engraftment of the transferred 89Zr-labeled cells was evaluated (n = 3).Results:89Zr-oxine-labeled bone marrow cells showed delayed proliferation, but differentiated normally. Transferred bone marrow cells rapidly migrated to the bone marrow, spleen, and liver (n = 5). Approximately 36% of donor cells homed to the bone marrow within 4 hours, irrespective of prior bone marrow ablation. Inhibition of CXCR4 by plerixafor alone or with G-CSF significantly blocked the bone marrow homing (P < 0.0001, vs. nontreated, at 2 hours), confirming a crucial role of the CXCR4-CXCL12 system. Mobilization of approximately 0.64% of pretransplanted bone marrow cells induced a 3.8-fold increase of circulating bone marrow cells. 89Zr-labeled donor cells engrafted as well as nonlabeled cells.Conclusions:89Zr-oxine PET imaging reveals rapid bone marrow homing of transferred bone marrow cells without impairment of their stem cell functions, and thus, could provide useful information for optimizing HSCT. Clin Cancer Res; 23(11); 2759-68. ©2016 AACR.