The microenvironment surrounding tumor cells has received considerable attention as a critical factor for brain tumor growth.1 In particular, the availability of nutrients in the tumor microenvironment may be important.2Brain tumors, both primary and metastatic, may have cystic compartments. In 2 studies, the presence of a cystic compartment was associated with a better survival rate in patients with glioblastoma multiforme (GBM).3,4 In 2 other, more recent studies, this was not the case.5,6 Depending on its content, especially of nutrients, the cyst fluid itself could be an important determinant for the growth potential of the surrounding tumor cells. However, only few quantitative biochemical studies have been performed on the cyst fluid of cystic, malignant brain tumors.
Malignant tumors, including GBMs, have a preference for glucose and glutamine as energy substrates.2 The only report on glucose in cyst fluid from malignant brain tumors seems to be that by Stern from 1939,7 who found glucose at 3 to 4 mmol/L in 2 cystic astrocytomas. Wieser et al8 showed the presence of glutamine, together with most other amino acids, in cyst fluid of both benign and malignant cystic brain tumors. B vitamins are indispensable cofactors, or precursors thereof, that are involved in energy metabolism and in various other enzymatic reactions in both normal and malignant cells.9,10 Their presence in tumor cyst fluid has to our knowledge never been investigated.
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