It is well known that artificial increase in expression of growth factors and their receptors can lead to tumorigenic transformation of cells. Additionally, multiple data on the increased expression of growth factors in many human and animal tumorigenic cells have been published. Nevertheless description of the functional role of endogenous growth factors in maintenance of tumorigenic phenotype remains obscure. Previously, we described a new model for studying neoplastic transformation and dormant metastasis. This model consists of cognate tumorigenic and nontumorigenic cell clones, the latter being obtained as a result of spontaneous reversion of tumorigenic ones. All revertant clones demonstrate the three well known features of normal cells: monolayer growth on a plastic, incapability to grow in soft agar with regular culture media with 10% FCS, and incapability to form tumors in syngeneic animals. Using RT-PCR, we measured expression ratios of main growth factors, commonly believed to be associated with malignization, in tumorigenic and revertant clones of our model. For some of these clones, we also measured an activity of growth factors in conditioned media. The data obtained argue that the levels of growth factor expression, measured by both the methods, are distributed between tumorigenic and revertant clones in a sporadic manner and do not correlate with cell tumorigenicity. Thus, our experimental observations enable us to consider the variability of growth factor expression as insignificant events in the reversion of tumorigenic cells to a nontumorigenic phenotype.