CXCL9 inhibits tumour growth and drives anti-PD-L1 therapy in ovarian cancer.

BACKGROUND: Response to immune checkpoint blockade (ICB) in ovarian cancer remains disappointing. Several studies have identified the chemokine CXCL9 as a robust prognosticator of improved survival in ovarian cancer and a characteristic of the immunoreactive subtype, which predicts ICB response. However, the function of CXCL9 in ovarian cancer has been poorly studied. METHODS: Impact of Cxcl9 overexpression in the murine ID8-Trp53-/- and ID8-Trp53-/-Brca2-/- ovarian cancer models on survival, cellular immune composition, PD-L1 expression and anti-PD-L1 therapy. CXCL9 expression analysis in ovarian cancer subtypes and correlation to reported ICB response. RESULTS: CXCL9 overexpression resulted in T-cell accumulation, delayed ascites formation and improved survival, which was dependent on adaptive immune function. In the ICB-resistant mouse model, the chemokine was sufficient to enable a successful anti-PD-L1 therapy. In contrast, these effects were abrogated in Brca2-deficient tumours, most likely due to an already high intrinsic chemokine expression. Finally, in ovarian cancer patients, the clear-cell subtype, known to respond best to ICB, displayed a significantly higher proportion of CXCL9high tumours than the other subtypes. CONCLUSIONS: CXCL9 is a driver of successful ICB in preclinical ovarian cancer. Besides being a feasible predictive biomarker, CXCL9-inducing agents thus represent attractive combination partners to improve ICB in this cancer entity.

Long-term maintenance of hematopoietic stem cells does not require contact with embryo-derived stromal cells in cocultures.

We recently established that two midgestation-derived stromal clones--UG26-1B6, urogenital ridge-derived, and EL08-1D2, embryonic liver-derived--support the maintenance of murine adult bone marrow and human cord blood hematopoietic repopulating stem cells (HSCs). In this study, we investigate whether direct HSC-stroma contact is required for this stem cell maintenance. Adult bone marrow ckit+ Ly-6C- side population (K6-SP) cells and stromal cells were cocultured under contact or noncontact conditions. These experiments showed that HSCs were maintained for at least 4 weeks in culture and that direct contact between HSCs and stromal cells was not required. To find out which factors might be involved in HSC maintenance, we compared the gene expression profile of EL08-1D2 and UG26-1B6 with four HSC-nonsupportive clones. We found that EL08-1D2 and UG26-1B6 both expressed 21 genes at a higher level, including the putative secreted factors fibroblast growth factor-7, insulin-like growth factor-binding proteins 3 and 4, pleiotrophin, pentaxin-related, and thrombospondin 2, whereas 11 genes, including GPX-3 and HSP27, were expressed at a lower level. In summary, we show for the first time long-term maintenance of adult bone marrow HSCs in stroma noncontact cultures and identify some secreted molecules that may be involved in this support.

Migration of iron oxide-labeled human hematopoietic progenitor cells in a mouse model: in vivo monitoring with 1.5-T MR imaging equipment.

PURPOSE: To evaluate the use of clinical 1.5-T magnetic resonance (MR) imaging equipment to depict the in vivo distribution of iron oxide-labeled human hematopoietic progenitor cells in athymic mice. MATERIALS AND METHODS: This study was approved by the ethical committee, and all women had given consent to donate umbilical cord blood for research. Twenty athymic female Balb/c mice underwent MR imaging before and 1, 4, 24, and 48 hours after intravenous injection of (1-3) x 10(7) human hematopoietic progenitor cells labeled with the superparamagnetic iron oxide particles ferumoxides through simple incubation (n = 10) or P7228 through lipofection (n = 10). Fifteen female Balb/c control mice were examined after intravenous injection of the pure contrast agents (n = 6 for both probes) or nonlabeled cells (n = 3). Signal intensities of liver, spleen, and bone marrow on MR images obtained before and after injection were measured and compared for significant differences by using the t test. MR imaging data were compared with the results of immunostaining against human CD31(+) cells and against the coating of the contrast agents; these results served as the standard of reference. RESULTS: Ferumoxides was internalized into more mature CD34(-) cells but not into CD34(+) stem cells, while P7228 liposomes were internalized into both CD34(-) and CD34(+) cells. After injection of iron oxide-labeled hematopoietic cells, a significant decrease in MR signal intensity was observed in liver and spleen at 1, 4, 24, and 48 hours after injection (P < .05) and in the bone marrow at 24 and 48 hours after injection (P < .05). The signal intensity decrease in bone marrow was significantly stronger after injection of iron oxide-labeled cells compared to controls that received injections of the pure contrast agent (P < .05). Results of histopathologic examination confirmed homing of iron oxide-labeled human progenitor cells in the murine recipient organs. CONCLUSION: The in vivo distribution of intravenously administered iron oxide-labeled hematopoietic progenitor cells can be monitored with 1.5-T MR imaging equipment.