Flavonoids for CMV-Induced Salivary Gland Tumor Therapy

Objectives: To determine the effect of baicalein, an "anti-viral/anti-cell signaling" flavonoid extensively used in Chinese herbal medicine, on cytomegalovirus (CMV)-host interactions, viral efficacy, and tumor pathology.
Methods: Newborn ex vivo 3D submandibular gland (SGs) were cultured in the presence or absence of mouse CMV (mCMV) on day 0 for 24 hours and then in virus-free media for a total of 10-14 days. Baicalein +/- the antiviral acyclovir were added daily on days 6-14. SG phenotypes, viral distribution, and viral-induced changes in key genes and proteins were analyzed using H&E histology, quantitative RT-PCR, and immunolocalization. A minimum of 3 independent samples/group/experiment were analyzed.
Results: Baicalein treatment of virus-infected SGs induced a marked decrease in pathology, cell proliferation and viral infection, a substantial increase in cell death in virally-infected cells, and significant changes in gene and protein expression. Specifically, baicalein inhibits the Shh and Fgf8/Fgfr3 pathways, normally upregulated by CMV infection. Baicalein also upregulates Cox2/Areg signaling, normally downregulated by CMV infection. Acyclovir treatment significantly reduces viral load, inhibits the Fgfr8/Fgfr3, Shh pathways, and the Cox2/Areg pathways; however, apoptosis is not seen. With combination treatment, morphology, viral load, and direction of changes in gene expression were similar to that seen with baicalein treatment alone.
Conclusions: Baicalein is an effective anti-CMV treatment, targeting the CMV-infected cells and not uninfected cells. By contrast, although acyclovir reduces viral load, it only slightly improves tumor pathology. Combined baicalein and acyclovir treatment reduces morphological and molecular phenotypes similar to those seen with baicalein alone. Our results indicate that the multi-targeting agent baicalein is effective in reducing viral load, tumor size, and pathology. What remains to be discovered is the molecular mechanism of flavonoid inhibition of viral infection and tissue pathology.