HAROLD P. RUSCH 



invasion and metastasis. The experiments of Algire (1), 

 Coman (15), and others provide stimulating leads. Further 

 work in this direction may lead to definitive experiments that 

 will permit us to understand how the invading cell evokes a 

 favorable vascular response and overcomes the forces that pre- 

 vent normal, growing tissues from overstepping the boundaries 

 that are compatible with the best interest of the host. 



Finally, since neoplasms in human beings usually retain 

 certain specialized features of the mature cell, the response of 

 such tumors to therapy must depend to a considerable extent on 

 the proportion of the retained characteristics. Therefore, no 

 chemotherapy screening program should depend entirely on 

 animal tumors which have suffered a considerable loss of 

 special functions through repeated transplantation. 



Conclusion 



It should be emphasized that the attack on the cancer 

 problem is a fine example of a research effort in which the 

 various branches of biological science cooperate in a common 

 cause and in which the old departmental classifications no 

 longer apply in a strict sense. The modern investigator of 

 malignant growth frequently brings to bear not only the dis- 

 ciplines of physiology and biochemistry but also the specialities of 

 genetics, embryology, bacteriology, pathology, virology, and 

 many others, which stimulate and nurture one another. 



The concept of carcinogenesis presented in this report was 

 based on facts which have emerged from numerous seemingly 

 unrelated investigations in these various fields. Such concepts 

 are worth while only if they engender additional advances, since 

 each advance is dependent on some prior gain made elsewhere, 

 and each advance, from the preliminary spadework to the 

 completed harvest, stimulates and catalyzes new advances. 



The report published in 1938 ended with a statement which 

 is still applicable today, "In any program for cancer research, 

 patience and the adoption of a long-time point of view are 

 absolutely essential." 



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