CXCL12 (SDF-1)/CXCR4 pathway in tumor. the CXCR4 inhibitor integrated the highest of both effects. The growth of the primary tumor was reduced to a similar extent as with chemotherapy only and metastasis formation was reduced to a similar extent as with CXCR4 inhibitor only. In conclusion, we demonstrate with this orthotopic mouse model the addition of a CXCR4 inhibitor to chemotherapy significantly reduces metastasis formation. Thus, it might improve the overall therapy response and consequently the outcome of SCLC individuals. . Whether the CXCL12-CXCR4 axis plays a role in metastasis formation and development of chemoresistance in individuals and thus may represent a good target in SCLC therapy remains unknown. In an orthotopic xenograft mouse model we investigated the effect of the CXCR4 inhibition on these processes. Our findings underscore the potential of CXCR4 inhibitors as antimetastatic providers in Cimetropium Bromide SCLC, only or in combination with standard therapy. RESULTS CXCL12-CXCR4 axis induces migration of SCLC cells we applied AMD3100 in the previously founded orthotopic mouse model. Intrathoracic injection of human being chemoresistant SCLC cells (H69-Luc-GFP) with this mouse model results in highly proliferative and invasive main tumors with a high capacity to metastasize. MRI scan was applied to monitor the increase in tumor quantities over time and to detect metastases. As formation of main tumors having a volume of 5-25 mm3 required two weeks, treatment with the CXCR4 inhibitor started at day time 14 after tumor inoculation. Due to the short biological half-life, AMD3100 (2.5 mg/kg) was administered intraperitoneally twice each day for five weeks. AMD3100 reduced the growth of already founded main tumors, but a complete regression of tumors was not accomplished. Five weeks after the start of treatment the mean tumor volume was significantly reduced by 61% in comparison to the control group (P=0.0167; Number ?Number2A).2A). Reduced tumor growth was confirmed using BLI (Number ?(Figure2B).2B). The treatment effectiveness was additionally analyzed by measuring metabolic activity of tumor cells in the terminal point of the experiment. To analyze glucose and amino acid uptake via PET scan we used two radiotracers FDG and FET, respectively. Although AMD3100 treatment potently reduced tumor growth, it did not show any effects on metabolic activity of tumor cells (Number ?(Figure2C).2C). Tumor cells in both organizations had an equal uptake of FDG and FET indicating the absence Cimetropium Bromide of cytotoxic effects of the treatment. Crucially, treatment with CXCR4 antagonists suppressed metastasis formation. The number of mice developing metastases was reduced by 43% (Number ?(Figure2D).2D). Seven out of 10 control mice developed metastases versus 3 out of 11 mice treated with AMD3100. In the control group a total amount of 13 metastases and in the treated group only 5 metastases were detected (Table ?(Table1).1). Immunhistochemical analysis of 13 main tumors and their metastases displayed no changes in manifestation of CXCR4 and CXCL12 upon AMD3100 treatment (Number ?(Number5).5). Related results were accomplished with main tumors developed from human being NCI-H446 cells (data not demonstrated). As in contrast to NCI-H69 cells using these cells there was no metastasis formation we did all the following experiments with NCI-H69 cells. Cimetropium Bromide Open in a separate windowpane Number CIP1 2 AMD3100 reduces the growth of the primary tumor and metastasis formationA. Tumor-bearing mice were treated twice each day with PBS vehicle control or 2.5 mg/kg AMD3100, starting at day 14 after tumor inoculation (control group n=7; treated group n=6). Treatment continued for five weeks. One representative effect out of three Cimetropium Bromide self-employed experiments is demonstrated. The related MR images are illustrated on the right panel. B. Treatment with AMD3100 reduces the progression of vital tumor cells in the terminal point. Right panel: representative BL images of control and AMD3100-treated mice at indicated time points. C. PET scan analysis displayed no difference in Cimetropium Bromide metabolic activity of tumor cells in the control (n=3) and AMD3100-treated group (n=3). D. AMD3100 treatment suppresses formation of metastases. Data are demonstrated as percentage of mice which developed spontaneous metastases (treated group n=11 and settings n=10). Table 1 Distribution of spontaneous metastases in different CXCL12-expressing organs (control group n=10; treated group n=11) thead th align=”center” valign=”middle” colspan=”2″ rowspan=”1″ control /th th align=”center” valign=”middle” colspan=”2″ rowspan=”1″ AMD3100 /th /thead Adrenal gland1?Adrenal gland1Liver9?Liver2Ovary1?Peritoneum2Peritoneum1Testis1 Open in a separate window Open in a separate window Number 5.