HHcy has been shown to affect blood-brain barrier (BBB) integrity through upregulation of matrix metalloproteinases (MMPs plays a key role in tumor invasion and metastasis by degrading various protein components in the extracellular matrix (ECM) and destroying the histological barrier to tumor cell invasion), where BBB integrity is mediated by miR-29b through regulation of DNMT3B (DNA methyltransferases 3B) which regulates the levels of MMP9 (matrix metalloproteinases 9, which is the largest molecular weight enzyme in the matrix metalloproteinase family) [19]. Here, MMP9 is linked to neoplasm.