The instant invention provides methods for treating a solid tumor in a subject comprising modulating nitric oxide production in the tumor to normalize tumor vasculature and administering an anti-tumor therapy to the subject. The invention further provides methods of treating a solid tumor in a subject comprising selectively increasing cyclic guanosine monophosphate (cGMP) or cGMP dependent protein kinase G production in the tumor vasculature to an amount effective to normalize tumor vasculature and administering an anti-tumor therapy to the subject.