A molecular basis for the synergy between 17-allylamino-17-demethoxy geldanamycin with Capecitabine and Irinotecan in human colorectal cancer cells through VEFG and MMP-9 gene expression

Anti-proliferative, anti-metastatic and anti-angiogenic effects of 17-allylamino-17-demethoxy
geldanamycin (17-AAG) were studied alone and in combination with Capecitabine (Cap)
and/or Irinotecan (IR) on HT-29 human colorectal carcinoma cells. Expression of MMP-9
(matrix metalloproteinase-9) and VEGF (vascular endothelial growth factor) mRNA was
analyzed by real-time PCR method. The study was further followed by wound scratch assay
for migration assessment. Nitric oxide content, MDA generation and total anti-oxidant
capacity were also assessed. Results showed significant differences between mono- and
double therapy (p ˂ 0.05). Combination of 17-AAG with IR or Cap resulted in synergistic
effect (Combination Index <1). Among double combination groups only Cap/17-AAG
showed significant differences in MMP-9 and VEGF genes expression and wound healing
assay. Moreover, a significant decrease of wound area in our triple combination group was
obtained, indicating the antagonistic effect. IR/17-AAG and IR/Cap double combination
groups resulted in down-regulation of MMP-9 and VEGF mRNA expression, respectively.
Significant generation of MDA and decrease in TAC values have been observed in all our
tested groups, however, the IR/17-AAG combination was the only group that could elevate
NO concentration, significantly. Our findings demonstrated potent anti-angiogenesis and
anti-metastatic effects for 17-AAG when it is provided in double combination especially with
Cap, suggesting a new protocol in colorectal cancer combination therapy. These findings
may indicate that down-regulation of VEGF and MMP-9 genes is directly related to
angiogenesis and metastasis.