Atypical tumor promoters

In an alternate form of tumor promotion, referred to as atypical tumor promoters (ATPs), elimination of the nascent clones may be blocked by inhibiting apoptosis [19], by failure to eliminate nascent transformed cells, or by failure to control an active infection (or activation of a latent viral infection [20]) of a carcinogenic virus. Host defense mechanisms are primarily responsible for regulating extrinsic apoptosis, cytotoxicity, and control of viral infections. If an IMBP were to mediate tumor promotion, it would be acting through such a mechanism. 

There are a number of host defense effector mechanisms, both humoral and cellular, that, when inhibited, have the potential to mediate atypical tumor promotion. These are listed in Table 27.4. As shown in the table, essentially all the effector cells of the immune system, with the exception of granulocytes, have the potential to eliminate nascent transformed cells or influence the... 

TABLE 27.4 Host defense effectors where inhibition by biopharmaceutical may mediate atypical tumor promotion... 

Defense Mechanism Putative Mechanism of Atypical Tumor Promotion Reference... 

As mentioned above, the mechanisms by which IMBPs are likely to act as atypical tumor promoters are all centered on their desired, albeit exaggerated,... 

TABLE 27.7 In vitro model systems for identification and characterization of atypical tumor promoters and tumor progression... 

In vitro Systems Example for Conventional Tumor Promoters Reference Example for Atypical Tumor Promoters or Their Targets Reference... 

Figure 27.1 Decision matrix for evaluation and classification of the hazard of IMBP acting as atypical tumor promoters.

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