Expression and prognostic value of JAM-A in gliomas

Abstract

Gliomas are among the most lethal cancers, being highly resistant to both chemo- and radiotherapy. The expression of junctional adhesion molecule-A (JAM-A) was recently identified on the surface of stem cell-like brain tumor-initiating cells and suggested to function as a unique glioblastoma niche adhesion factor influencing the tumorigenic potential of brain tumor-initiating cells. We have recently identified high JAM-A expression to be associated with poor outcome in glioblastomas, and our aim was to further investigate the expression of JAM-A in gliomas focusing especially on the prognostic value in WHO grade II and III gliomas. JAM-A protein expression was evaluated by immunohistochemistry and advanced quantitative image analysis with continuous estimates of staining intensity. The JAM-A antibody stained tumor cell membranes and cytoplasm to various extent in different glioma subtypes, and the intensity was higher in glioblastomas than low-grade gliomas. We could not detect an association with overall survival in patients with grade II and III tumors. Double-immunofluorescence stainings in glioblastomas revealed co-expression of JAM-A with CD133, SOX2, nestin, and GFAP in tumor cells as well as some co-expression with the microglial/macrophage marker IBA-1. In conclusion, JAM-A expression was higher in glioblastomas compared to low-grade gliomas and co-localized with recognized stem cell markers suggesting an association of JAM-A with glioma aggressiveness. No significant association between JAM-A expression and overall survival was found in grade II and III gliomas. Further research is needed to determine the function and clinical impact of JAM-A in gliomas.

Keywords: Astrocytic brain tumors; Glioma; Junctional adhesion molecule-A; Prognosis; Tumor stem cell.

Fig. 1

Examples of JAM-A staining in normal brain and WHO grade II-IV gliomas, immunohistochemically stained with JAM-A antibody. a Subventricular zone (SVZ) with positive ependymal layer. b Weak neuronal staining was seen in cortex. c Few positive cells were observed in white matter. d Diffuse astrocytoma (DA) with moderate staining showing positive gemistocytes. e Oligodendroglioma (OD) with moderate staining intensity. f and g Anaplastic astrocytoma (AA) and anaplastic oligodendroglioma (AOD) with moderate staining intensity. h and i Glioblastoma (GBM) with giant cells showing moderate staining intensity, and glomeruloid vessels with staining of the endothelium as well as stained cells with tumor cell morphology. Scale bar 100 µm

Fig. 2

Association of JAM-A intensity with tumor type. Using immunohistochemical staining JAM-A+ tumor cells were identified. a and b When the original image was processed and the algorithm applied, nuclei of JAM-A+ cells were represented by green and perinuclear areas by light blue. The staining intensity was measured in the perinuclear area. c In the RSD glioma cohort, JAM-A intensity increased with tumor grade and was higher in gliomas compared to normal brain tissue. d No difference was seen among the different types of gliomas in the RSD glioma cohort. e and f In the OUH astrocytoma cohort, JAM-A intensity in DAs and AAs did not differ significantly from each other, and similar was found when subdividing the tumors based on IDH status. *p-value < 0.05, ***p-value < 0.001. The vertical lines indicate mean +/− standard error of the mean. AA anaplastic astrocytoma, AOD anaplastic oligodendroglioma, DA diffuse astrocytoma, GBM glioblastoma, mIDH mutated isocitrate dehydrogenase, NBT normal brain tissue, OD oligodendroglioma, OUH Odense University Hospital, RSD Region of Southern Denmark, wtIDH wildtype isocitrate dehydrogenase

Fig. 3

Association between JAM-A intensity and overall survival. Kaplan–Meier curves for patients with a WHO grade II and b grade III glioma in the RSD glioma cohort. Kaplan–Meier curves for patients with c DA and d AA in the RSD glioma cohort. Kaplan–Meier curves for patients with e DA and f AA in the OUH astrocytoma cohort. AA anaplastic astrocytoma, DA diffuse astrocytoma, OUH Odense University Hospital, RSD Region of Southern Denmark

Fig. 4

Co-expression of JAM-A in glioblastomas using immunofluorescence. a–d JAM-A/CD133 co-expression was seen, and e–h JAM-A/SOX2 co-expression was observed in some areas of the glioblastomas. i–l Most tumor cells did not express both JAM-A and nestin. m–p JAM-A+ cells rarely expressed GFAP. q–t The microglial/macrophage marker IBA-1 was expressed by a few JAM-A+ cells. Scale bar 50 µm