Transformation of human embryonic kidney cells by human papovarirus BK

Abstract

Infection of secondary human embryonic kidney (HEK) cells with human papovavirus BK (BKV) resulted in cellular lysis and degeneration within 7 days. After 30 days, multilayered colonies of transformed cells were found and subcultured for analyses. These BK-HEK cells uniformly expressed the BKV T-antigen but were only 1% V-antigen positive. They produced infectious virus and were resistant to superinfection by BKV. They reached a saturation density of 1.3 x 10(5) cells per cm2 in medium with 5% fetal calf serum, were able to grow in medium containing 2% serum, and did not form colonies in soft agar or tumors in nude mice. Nonintegrated, superhelical BKV DNA was detected in the noncloned cells as expected because they were persistently infected and contained RNA transcripts complementary to both early and late regions of the BKV genome. Analysis of T-antigen-positive clonal isolates of these BK-HEK cells by the Southern technique revealed an absence of free viral DNA and the presencce of integrated BKV DNA sequences corresponding to the early region of the BKV genome. These studies demonstrate the stable transformation of human cells by BKV. However, the transformed human cells which retain and express part of the BKV genome do not fully manifest the growth properties of other papovarirus-transformed cells.

Episomal DNA of a BK virus variant in a human insulinoma

“…Seroconversion generally occurs during childhood, and in some instances a pathological condition has been correlated with the primary infection [Mantyjarvi et al, 1973;Van der Noorda and Vertheim-van Dillen, 1977;Goudsmit et al, 19811. Neoplastic transformation of hamster, mouse, rat, and rabbit cells was obtained by infection in vitro with BKV or BKV DNA [Major and Di Mayorca, 1973;Portolani et al, 1975;Van der Noorda, 1976;Tanaka et al, 1976;Takemoto and Martin, 1976;Mason and Takemoto, 1977;Portolani et al, 19781. Although monkey and human cells are permissive for BKV replication [Takemoto and Mullarkey, 19731 and lyse upon infection with virus or viral DNA, they have been transformed by BKV [Portolani et al, 1978;Purchio and Fareed, 1979;Takemoto et al, 1979;Grossi et al, 19821. BKV is highly oncogenic in hamsters and mice (see Howley [ 19801 and Padgett [ 19801 for reviews) displaying a remarkable tropism for particular tissues and organs.…”

Induction of senescence and control of tumorigenicity in BK virus transformed mouse cells by human chromosome 6

“…However, in most of these experiments, although the cells showed a morphologically transformed phenotype and an extended life span, they were not immortalized and did not produce tumors in nude mice (Portolani et al, 1978;Corallini et al, 1991). In cases where continuous cell lines were obtained, immortalization occurred at a very low frequency and after a long latency period (Purchio and Fareed, 1979;Takemoto et al, 1979;Grossi et al, 1982). T h e different susceptibility of rodent and human cells to BKV transformation may depend on cellular factors controlling the transformation process.…”

Transformation of Human Embryonic Kidney Cells by a Viable Deletion Mutant of BK Virus

“…The present study demonstrates that HEK cultures originating from different fetuses were transformed by a viable deletion mutant of BKV (pm-522) but not by a cloned wild-type BKV (wt-50 I). Previous attempts to transform HEK cells by using a plaque isolate of BKV or a BKV stock derived from Gardner strain either succeeded (7) or failed (6). These results taken together may imply that some variants of BKV can efficiently transform permissive HEK cells, wheras wild-type BKV cannot.…”

“…Although the existence of a few copies of integrated viral sequences in pmHEK cells was not ruled out, the large amount of free viral DNA present in each cell probably plays a prominent role in the production of T antigen required for maintenance of transformation. Three recent reports (3,7,10) have described transformation of perrmssive human cells by human papovavirus BK (BKV) (5). From human embryonic kidney (HEK) cells, Purchio and Fareed (7) obtained stable cell lines displaying transformed properties.…”

“…Three recent reports (3,7,10) have described transformation of perrmssive human cells by human papovavirus BK (BKV) (5). From human embryonic kidney (HEK) cells, Purchio and Fareed (7) obtained stable cell lines displaying transformed properties. These cells uniformly expressed tumor (T) antigen but capsid (V) antigen was detected in only a minority of the cells.…”