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Modeling cytomegalovirus infection in mouse tumor models.

Price RL, Chiocca EA - Front Oncol (2015)

Bottom Line: These findings are controversial as several groups have also reported inability to replicate these results.These models recapitulate for the most part intratumoral CMV expression as seen in human tumors.Additionally, we discovered that CMV infection in Trp53(-/+) mice promotes pleomorphic rhabdomyosarcomas.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurological Surgery, Washington University , St. Louis, MO , USA.

ABSTRACT
The hypothesis that cytomegalovirus (CMV) modulates cancer is evolving. Originally discovered in glioblastoma in 2002, the number of cancers, where intratumoral CMV antigen is detected, has increased in recent years suggesting that CMV actively affects the pathobiology of certain tumors. These findings are controversial as several groups have also reported inability to replicate these results. Regardless, several clinical trials for glioblastoma are underway or have been completed that target intratumoral CMV with anti-viral drugs or immunotherapy. Therefore, a better understanding of the possible pathobiology of CMV in cancer needs to be ascertained. We have developed genetic, syngeneic, and orthotopic malignant glioma mouse models to study the role of CMV in cancer development and progression. These models recapitulate for the most part intratumoral CMV expression as seen in human tumors. Additionally, we discovered that CMV infection in Trp53(-/+) mice promotes pleomorphic rhabdomyosarcomas. These mouse models are not only a vehicle for studying pathobiology of the viral-tumor interaction but also a platform for developing and testing cancer therapeutics.

No MeSH data available.


Related in: MedlinePlus

MCMV analysis of mouse tumors. (A) PCR for MCMV DNA in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (B) RT-PCR for MCMV-IE1 in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (C) RT-PCR product fidelity was validated by sequencing the amplified MCMV-IE1. (D) MCMV-IE1 immunohistochemistry in MCMV- and Mock-infected tumor. Scale bars = 50 μm. Reprinted by permission from the American Association for Cancer Research: Price et al. (17).
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Figure 3: MCMV analysis of mouse tumors. (A) PCR for MCMV DNA in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (B) RT-PCR for MCMV-IE1 in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (C) RT-PCR product fidelity was validated by sequencing the amplified MCMV-IE1. (D) MCMV-IE1 immunohistochemistry in MCMV- and Mock-infected tumor. Scale bars = 50 μm. Reprinted by permission from the American Association for Cancer Research: Price et al. (17).

Mentions: In addition to malignant gliomas, we are interested in studying the role of CMV in other tumors. Many human tumor types are deficient in the p53 tumor suppressor. Trp53−/+ mice were derived from Mut3 mice. Published data show that Trp53−/+ mice develop variable tumors at a late age. Tumors from these mice range from lymphomas to fibrosarcomas, and only rarely result in RMS (<10% of the time) (41). We infected these mice neonatally with MCMV, similarly to our malignant glioma studies, or at 4 weeks of age (106 p.f.u.s) to simulate early adult MCMV infection. Since Trp53−/+ mice start developing tumors at a late age (>9 months), we terminated experiments at 9 months of age to detect MCMV-specific effects on tumor development. We hypothesized that MCMV would lead to an earlier tumor onset. Neonatal MCMV infection was associated with a statistically significant increase in tumor occurrence compared to mock-infected mice. In fact, only 1 mock-infected out of 27 mice developed a tumor during our study. In contrast, 42.8% (12/28) of neonatally MCMV-infected Trp53−/+ mice developed tumors at significantly earlier time points when compared to mock-infected mice. Interestingly, 84.6% (10/12) of these tumors were pleomorphic RMS. This data suggest that, not only does MCMV accelerate tumor formation in mice with heterozygous Trp53 mutation but preferentially leads to formation of pleomorphic RMS as opposed to other types of cancer. Mice infected as adults did not show increased tumor incidence indicating that adult infection does not promote tumor formation. Analysis of these tumors demonstrated that MCMV genetic material was present in tumors as was observed in human tumors. MCMV-infected mice revealed the presence of viral DNA (Figure 3A) in all tumors tested, but not in the mock-infected Trp53−/+ mouse. Additionally, early gene MCMV-IE1 transcripts were present in most tumors, whereas a gene transcribed later in the replication cycle, MCMV-GB, was not detected (Figure 3B and not shown). We do not know why this late gene was not transcribed, but this suggests that full viral replication is not occurring. Instead, the virus is only transcribing certain early transcripts. Sequencing of the transcription product from RT-PCR reactions of MCMV-IE1 RNA revealed that the transcripts sequenced from the tumor matches the stock virus injected into the mice (Figure 3C). Furthermore, MCMV-infected tumors expressed IE1 protein (Figure 3D). Strong intratumoral IHC staining corroborates the human data. Taken together, these data show transcriptionally active MCMV within RMS tumors, which could modulate the tumor. These data suggest a role of CMV in RMS development. Our data show for the first time that CMV infection combined with Trp53 heterozygosity promotes pleomorphic RMS. Furthermore, the idea that CMV can promote tumorigenesis in an organism with genetic aberrations, such as loss of a tumor suppressor, may help to explain the difficulty of epidemiologically linking CMV infection with relatively rare cancers.


Modeling cytomegalovirus infection in mouse tumor models.

Price RL, Chiocca EA - Front Oncol (2015)

MCMV analysis of mouse tumors. (A) PCR for MCMV DNA in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (B) RT-PCR for MCMV-IE1 in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (C) RT-PCR product fidelity was validated by sequencing the amplified MCMV-IE1. (D) MCMV-IE1 immunohistochemistry in MCMV- and Mock-infected tumor. Scale bars = 50 μm. Reprinted by permission from the American Association for Cancer Research: Price et al. (17).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4362273&req=5

Figure 3: MCMV analysis of mouse tumors. (A) PCR for MCMV DNA in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (B) RT-PCR for MCMV-IE1 in tumors from MCMV (n = 4) and mock-infected (n = 1) mice. (C) RT-PCR product fidelity was validated by sequencing the amplified MCMV-IE1. (D) MCMV-IE1 immunohistochemistry in MCMV- and Mock-infected tumor. Scale bars = 50 μm. Reprinted by permission from the American Association for Cancer Research: Price et al. (17).
Mentions: In addition to malignant gliomas, we are interested in studying the role of CMV in other tumors. Many human tumor types are deficient in the p53 tumor suppressor. Trp53−/+ mice were derived from Mut3 mice. Published data show that Trp53−/+ mice develop variable tumors at a late age. Tumors from these mice range from lymphomas to fibrosarcomas, and only rarely result in RMS (<10% of the time) (41). We infected these mice neonatally with MCMV, similarly to our malignant glioma studies, or at 4 weeks of age (106 p.f.u.s) to simulate early adult MCMV infection. Since Trp53−/+ mice start developing tumors at a late age (>9 months), we terminated experiments at 9 months of age to detect MCMV-specific effects on tumor development. We hypothesized that MCMV would lead to an earlier tumor onset. Neonatal MCMV infection was associated with a statistically significant increase in tumor occurrence compared to mock-infected mice. In fact, only 1 mock-infected out of 27 mice developed a tumor during our study. In contrast, 42.8% (12/28) of neonatally MCMV-infected Trp53−/+ mice developed tumors at significantly earlier time points when compared to mock-infected mice. Interestingly, 84.6% (10/12) of these tumors were pleomorphic RMS. This data suggest that, not only does MCMV accelerate tumor formation in mice with heterozygous Trp53 mutation but preferentially leads to formation of pleomorphic RMS as opposed to other types of cancer. Mice infected as adults did not show increased tumor incidence indicating that adult infection does not promote tumor formation. Analysis of these tumors demonstrated that MCMV genetic material was present in tumors as was observed in human tumors. MCMV-infected mice revealed the presence of viral DNA (Figure 3A) in all tumors tested, but not in the mock-infected Trp53−/+ mouse. Additionally, early gene MCMV-IE1 transcripts were present in most tumors, whereas a gene transcribed later in the replication cycle, MCMV-GB, was not detected (Figure 3B and not shown). We do not know why this late gene was not transcribed, but this suggests that full viral replication is not occurring. Instead, the virus is only transcribing certain early transcripts. Sequencing of the transcription product from RT-PCR reactions of MCMV-IE1 RNA revealed that the transcripts sequenced from the tumor matches the stock virus injected into the mice (Figure 3C). Furthermore, MCMV-infected tumors expressed IE1 protein (Figure 3D). Strong intratumoral IHC staining corroborates the human data. Taken together, these data show transcriptionally active MCMV within RMS tumors, which could modulate the tumor. These data suggest a role of CMV in RMS development. Our data show for the first time that CMV infection combined with Trp53 heterozygosity promotes pleomorphic RMS. Furthermore, the idea that CMV can promote tumorigenesis in an organism with genetic aberrations, such as loss of a tumor suppressor, may help to explain the difficulty of epidemiologically linking CMV infection with relatively rare cancers.

Bottom Line: These findings are controversial as several groups have also reported inability to replicate these results.These models recapitulate for the most part intratumoral CMV expression as seen in human tumors.Additionally, we discovered that CMV infection in Trp53(-/+) mice promotes pleomorphic rhabdomyosarcomas.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurological Surgery, Washington University , St. Louis, MO , USA.

ABSTRACT
The hypothesis that cytomegalovirus (CMV) modulates cancer is evolving. Originally discovered in glioblastoma in 2002, the number of cancers, where intratumoral CMV antigen is detected, has increased in recent years suggesting that CMV actively affects the pathobiology of certain tumors. These findings are controversial as several groups have also reported inability to replicate these results. Regardless, several clinical trials for glioblastoma are underway or have been completed that target intratumoral CMV with anti-viral drugs or immunotherapy. Therefore, a better understanding of the possible pathobiology of CMV in cancer needs to be ascertained. We have developed genetic, syngeneic, and orthotopic malignant glioma mouse models to study the role of CMV in cancer development and progression. These models recapitulate for the most part intratumoral CMV expression as seen in human tumors. Additionally, we discovered that CMV infection in Trp53(-/+) mice promotes pleomorphic rhabdomyosarcomas. These mouse models are not only a vehicle for studying pathobiology of the viral-tumor interaction but also a platform for developing and testing cancer therapeutics.

No MeSH data available.


Related in: MedlinePlus