Tumor angiogenesis factor (TAF) and its importance in determining a strategy for
cancer chemotherapy are discussed. It is suggested that inhibition of
RNA synthesis or increased
RNA catabolism might interfere with the metabolism of solid
tumor cells more so than in normal cells, and thus hinder angiogenesis and pursuant
tumor growth by preventing the synthesis of the
RNA component of TAF. An attempt is made to indicate potential models for anti-angiogenesis agents of this type. The drugs offered as initial prototypes for investigations along these lines are
actinomycin D (which likely has
antimetabolite and anti-angiogenesis activities),
polyriboinosinic-polyribocytidylic acid (which likely has adjuvant and anti-angiogenesis activities) and
ribonuclease (which in theory might be a purely
anti-angiogenetic agent). It is noted that these models may turn out to be less than ideal as therapeutic agents due to problems of toxicity, metabolism, potency, or distribution, but nonetheless might serve to yield insights into the design of new
cancer chemotherapeutic drugs. In addition, some evidence is cited suggesting that
actinomycin D may be more effective against certain
tumors when employed in lower, chronic dosages rather than its present use in "loading" dosages.The concept of anti-angiogenesis agents as fundamentally "tumoristatic"
therapies is discussed, and the likelihood that such agents might be effectively "tumoricidal" in immunocompetent hosts is mentioned. The main promise of an anti-angiogenetic strategy is efficacy against presently intractable slowly growing human
cancers when used in combination with other treatment modalities. In summary, a strategy of
cancer chemotherapy predicated upon interference with
RNA synthesis or increase in
RNA catabolism is offered as a potential mechanism for establishing anti-angiogenesis, and as a promising alternative and adjunct to present methods.