XBP1 and meningioma: Thus, XBP1 upregulation may be attributed to its role as a key component of the ER stress pathway,37 which is activated to resolve protein folding errors and restore the stability of the intracellular environmen.38 Moreover, XBP1 upregulation may affect immune cell function in the meningioma microenvironment, including the activation status of macrophages and NK cells, as well as their ability to recognize and clear tumour cells.