Ecotropic C-type retrovirus of B16 melanoma and malignant transformation of normal melanocytes

Li, Mengfeng; Xu, Fan; Müller, Jacqueline; Hearing, Vincent J.; Gorelik, Elieser

doi:10.1002/(sici)1097-0215(19980504)76:3<430::aid-ijc23>3.0.co;2-d

Cited by 24 publications

(21 citation statements)

References 21 publications

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“…The biological significance of MelARV remains to be further clarified. We previously demonstrated that in vitro infection of a normal melanocyte line with MelARV could induce malignant transformation (27). However, this transformation was a relatively rare event, and in most cases infection of melanocytes resulted in expression of MAA but without malignant transformation.…”

Section: Discussionmentioning

confidence: 99%

“…Melan-A melanocytes that were transformed by v-ras Ha transfection (40) were termed Mel-ras. Meli-A1 and Meli-BL melanomas were obtained by infection of the Melan-A line and Melan-BL lines with MelARV (27). All melanomas were maintained in complete RPMI 1640 medium.…”

Section: Methodsmentioning

confidence: 99%

“…In two cases, melanocytes showed morphological changes and were able to grow in vitro in the absence of TPA and after inoculation into mice, formation of the progressively growing highly pigmented tumors was observed. These MelARV-transformed melanomas were termed Meli-A and Meli-BL, respectively (27).…”

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confidence: 99%

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Sequence and Insertion Sites of Murine Melanoma-Associated Retrovirus

Huang

Zhu

et al. 1999

J Virol

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We previously showed that B16 melanoma cells produce ecotropic melanoma-associated retrovirus (MelARV) which encodes a melanoma-associated antigen recognized by MM2-9B6 monoclonal antibody. The biological significance of MelARV in melanoma formation remains unknown. We found that infection of normal melanocytes with MelARV resulted in malignant transformation. It is likely that MelARV emerged from the defective Emv-2 provirus, a single copy of ecotropic provirus existing in the genome of C57BL/6 mice. In the present study, we cloned and sequenced the full-length MelARV genome and its insertion sites and we completed sequencing of the Emv-2 provirus. Our data show that MelARV has a typical full-length retroviral genome with high homology (98.54%) to Emv-2, indicating a close relationship between both viruses. MelARV probably emerged as a result of recombination between Emv-2 and an endogenous nonecotropic provirus. Some observed differences in the gag and polregions of MelARV might account for the restoration of productivity and infectivity of a novel retrovirus that somatically emerged during melanoma formation. MelARV does not contain any oncogene and therefore might induce transformation by insertional mutagenesis. We sequenced two insertion sites of MelARV. The first insertion site represents the 3′ coding region of the c-maf proto-oncogene at 67.0 centimorgans (cM) on chromosome 8. The c-mafproto-oncogene encodes a basic leucine zipper protein homologous to c-fos and c-jun. Insertion of MelARV in BL6 melanoma cells resulted in the up-regulation of c-maf. It is noteworthy that the Emv-2 provirus is also inserted into a noncoding region at 61.0 cM on the same chromosome 8. The second insertion site is the 3′ noncoding region of the DNA polymerase gamma (PolG) gene on chromosome 7. The expression of PolG was not affected by the MelARV insertion. Further investigation of the biological significance of MelARV in melanoma formation is being undertaken.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Sequence and Insertion Sites of Murine Melanoma-Associated Retrovirus

Huang

Zhu

et al. 1999

J Virol

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“…Two infected melanocyte lines were transformed and formed highly pigmented tumors in mice (Li et al, 1998). Analysis of the retrovirus insertion sites revealed that in BL6 and in novel retrovirus-induced melanomas proto-oncogene c-maf is a common insertion site (Li et al, 1998). These data suggest that C-type melanoma-associated retroviruses might play a role in melanoma formation, probably by insertion and activation of the proto-oncogene expression.…”

Section: Introductionmentioning

confidence: 88%

“…Recently we tested the potential role of the melanoma-associated retroviruses in malignant transformation by infection of the cultured melanocyte lines of C57BL/6 mice with MelARV isolated from the supernatant of cultured BL6 melanoma. Two infected melanocyte lines were transformed and formed highly pigmented tumors in mice (Li et al, 1998). Analysis of the retrovirus insertion sites revealed that in BL6 and in novel retrovirus-induced melanomas proto-oncogene c-maf is a common insertion site (Li et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Loss of Retrovirus Production in JB/RH Melanoma Cells Transfected with H-2Kband TAP-1 Genes

Müller³

et al. 1999

Virology

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JB/RH1 melanoma cells, as well as other melanomas of C57BL/6 mice (B16 and JB/MS), express a common melanoma-associated antigen (MAA) encoded by an ecotropic melanoma-associated retrovirus (MelARV). JB/RH1 cells do not express the H-2Kb molecules due to down-regulation of the H-2Kb and TAP-1 genes. When JB/RH1 cells were transfected with the H-2Kb and cotransfected with the TAP-1 gene, it resulted in the appearance of H-2Kb molecules and an increase in their immunogenicity, albeit they lost expression of retrovirus-encoded MAA recognized by MM2-9B6 mAb. Loss of MAA was found to result from a complete and stable elimination of ecotropic MelARV production in the H-2Kb/TAP-1-transfected JB/RH1 cells. Northern blot analysis showed no differences in ecotropic retroviral messages in MelARV-producing and -nonproducing melanoma cells, suggesting that loss of MelARV production was not due to down-regulation of MelARV transcription. Southern blot analysis revealed several rearrangements in the proviral DNA of H-2Kb-positive JB/RH1 melanoma cells. Sequence analysis of the ecotropic proviral DNA from these cells showed numerous nucleotide substitutions, some of which resulted in the appearance of a novel intraviral PstI restriction site and the loss of a HindIII restriction site in the pol region. PCR amplification of the proviral DNAs indicates that an ecotropic provirus found in the H-2Kb-positive cells is novel and does not preexist in the parental H-2Kb-negative melanoma cells. Conversely, the ecotropic provirus of the parental JB/RH1 cells was not amplifable from the H-2Kb-positive cells. Our data indicate that stable loss of retroviral production in the H-2Kb/TAP-1-transfected melanoma cells is probably due to the induction of recombination between a productive ecotropic MelARV and a defective nonecotropic provirus leading to the generation of a defective ecotropic provirus and the loss of MelARV production and expression of the retrovirus-encoded MAA.

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High level antibody response to retrovirus-associated but not to melanocyte lineage-specific antigens in mice protected against B16 melanoma

et al. 1999

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Mice vaccinated with Mycobacterium tuberculosis Ag38 gene‐transduced B16 melanoma cells showed significant protection from intravenous challenge with parental B16 melanoma cells. No cytotoxic T‐cell activity was found against melanoma cells, although the endogenous presence of the mycobacterial gene induced a preferential Th1 response. After immunization, a low serological response against melanoma cells was detected, while a high titer of antibodies directed to parental B16 cells, mainly of IgG2a isotype, was found in protected mice after challenge. These antibodies exhibited complement‐dependent cytotoxicity against melanoma cells in vitro, while in vivo, used in passive immunization, they induced a decrease in a number of experimental B16 lung metastases. Most of the antibodies were directed against endogenous murine leukemia viruses. No reactivity against melanocyte lineage‐specific antigens was observed. In particular, no reactivity was found in sera from protected mice against tyrosinase‐related protein 2 (TRP‐2), either stably expressed in a non‐melanoma cell line or obtained by in vitro transcription‐translation, or against tyrosinase, TRP‐1 and gp100 antigens immunoprecipitated from B16 cells. Thus, in the B16 murine model, the presence of dominant viral antigens induces a very strong humoral response that might be protective and may inhibit or mask the presence of minor clonotypes. Int. J. Cancer 83:107–112, 1999. © 1999 Wiley‐Liss, Inc.

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Ecotropic C-type retrovirus of B16 melanoma and malignant transformation of normal melanocytes

Cited by 24 publications

References 21 publications

Sequence and Insertion Sites of Murine Melanoma-Associated Retrovirus

Sequence and Insertion Sites of Murine Melanoma-Associated Retrovirus

Loss of Retrovirus Production in JB/RH Melanoma Cells Transfected with H-2Kband TAP-1 Genes

High level antibody response to retrovirus-associated but not to melanocyte lineage-specific antigens in mice protected against B16 melanoma

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