SIPA1L1 and Anaplastic (Malignant) Meningioma: On the other hand, SIPA1L1 has also been described as a potential tumor suppressor (Gao et al., 1999) since it is located on a region in chromosome 14 which has been reported to exhibit a loss of heterozygosity in malignant meningiomas (Menon et al., 1997).