Table 2.

Distribution of the Expression of VEGF, flt-1, flk-1, tie-1, and tie-2 mRNA in Normal Brain, Low-Grade Lesions and High-Grade Tumors of GFAP-v-src Transgenic Mice, and in GFAP-v-src × p53^+/− and GFAP-v-src × Rb^+/− Double Transgenic Mice

Sample	VEGF	flt-1	flk-1	tie-1	tie-2
1	−	+	−	−	−
2	++	++*	+	+	+
3	++	++*	+	−	−
4	++	+	+	−	−
5	++	++*	+	+	−
6	+	n.d.	−	n.d.	n.d.
7	++	+*	++	−	−
8	++	+	−	−	−
9	n.d.	++	+	n.d.	+
10	++	+*	+	−	+
11	++	+*	+	−	−
12	++	+++	++	+	−
13	+++	+++	+++	++	+
14	++	+++	+++	++	++
15	+++	++	n.d.	+	−
16	++	n.d.	++	++	+
17	+++	+	+	+	+
18	++	+++	++	+	−
19	+++	++	+++	−	+
20	++	+	+	+	+

v-src and VEGF were expressed in neoplastic astrocytes, whereas flt-1, flk-1, tie-1, and tie-2 were expressed only in endothelial cells. Surprisingly, we found that some low-grade gliomas expressed flt-1 also in neoplastic astrocytes (*).

Semiquantitative evaluation of expression: −, no expression detectable; +, weak expression, at the threshold of detectability; ++, clearly detectable expression; +++, strong expression; n.d., not determined.