Fig. 6: FPS-ZM1 radiosensitizes experimental and human brain metastases.

a, Schema of experimental design. H2030-BrM cells were inoculated IC into nude mice, and 2 weeks later, mice received 10 doses of 3 Gy WBRT plus 500 mg kg⁻¹ per day FPS-ZM1 or vehicle until the end of the experiment. Intracranial tumor growth was monitored weekly with BLI. b, Representative bioluminescence images in vivo and ex vivo (brains) of control and experimental arms at endpoint, 5 weeks after IC injection. BLI scale bars correspond to in vivo (top) and ex vivo (bottom). Colors bar show BLI intensity in p s⁻¹ cm⁻² sr⁻¹). c, Quantification of in vivo photon flux values from the head of mice inoculated with H2030-BrM cells that received WBRT plus vehicle or FPS-ZM1, as depicted in a. BLI was performed at three different time points during the course of treatment (weeks 1, 3 and 5). Values are shown in box-and-whisker plots, where every dot represents a different brain and the line in the box corresponds to the median. The boxes go from the upper to the lower quartiles, and the whiskers go from the minimum to the maximum value (n = 18, vehicle + γ-IR; n = 21, FPS-ZM1 + γ-IR). P value was calculated using two-tailed Mann–Whitney test. d, Schema of experimental design. Surgically resected human brain metastases from patients who relapsed after receiving previous local treatments, including WBRT, were used to measure S100A9 levels by immunofluorescence (IF) and establish PDOCs, which were treated with FPS-ZM1 (10 µM) with or without irradiation and the therapeutic benefit evaluated 3 days later by 5-bromodeoxyuridine (BrdU) incorporation in cancer cells. e, Quantification of BrdU⁺ cancer cells in PDOCs from patient 2 treated with FPS-ZM1 and/or irradiation. Values are shown in box-and-whisker plots, where every dot represents an independent culture and the line in the box corresponds to the median. The boxes go from the upper to the lower quartiles, and the whiskers go from the minimum to the maximum value (n = 6, DMSO; n = 6, FPS-ZM1, n = 6, γ-IR; n = 6, FPS-ZM1 + γ-IR). P values were calculated using a two-tailed t-test. f, Heatmap depicting the quantification of BrdU⁺ cancer cells in PDOCs derived from seven patients with relapsed brain metastases, which have S100A9 high levels. Each row represents an individual patient, and each column represents different treatment conditions. Color-coded values are percentages of BrdU⁺ cancer cells normalized to the DMSO condition of each patient. P value was calculated using a two-tailed t-test. g, Schema of experimental design. Tumor-naive C57BL/6 mice received 10 doses of 3 Gy WBRT plus 500 mg kg⁻¹ per day FPS-ZM1 or vehicle for 3 weeks. One month later, mice underwent health assessment, imaging and behavioral testing. h, Quantification of the time spent to escape the water to the platform (escape latency) from different groups of mice. Values are shown in a temporal scale, where each dot represents the mean value for each group in a given day of the test and the error bars represent s.e.m. (n = 6, control; n = 13, vehicle + γ-IR, n = 20, FPS-ZM1 + γ-IR). Calculation of P values is detailed in Supplementary Table 24. i, Representative ex vivo ultrahigh-field MRI images of brains from mice treated with either WBRT + vehicle or WBRT + FPS-ZM1 are shown. Greyscale shows the values from the long T2 component by ex vivo ultrahigh-field MRI. j, Quantification of whole-brain myelin water fraction by ex vivo ultrahigh-field MRI in brains from experiment depicted in i. Values are shown in box-and-whisker plots, where every dot represents a brain and the line in the box corresponds to the median. The boxes go from the upper to the lower quartiles, and the whiskers go from the minimum to the maximum value (n = 5, each experimental condition). P value was calculated using a two-tailed t-test.