The present invention relates to a mesothelin binding protein for use in the treatment of brain cancer in a patient, wherein said mesothelin binding protein comprises an epitope binding domain which specifically binds to an epitope containing amino acid sequence that is similar or identical to a section of the amino acid sequence of mammalian mesothelin precursor, in particular human mesothelin precursor (SEQ ID NO: 1). The invention further relates to a CAR T-cell, and expanded T-cell or a cancer vaccine comprising a mesothelin binding protein for use in brain cancer therapy. Finally, the invention relates to a method for diagnosing a patient suspected of a brain tumor.
