How Tumour Viruses Usurp Signalling Pathways (S2, W10)
Epstein-Barr Virus (EBV)
15-20% of cancer caused by infectious agents, 10-15% caused by virus infection.
EBV a gamma herpesvirus, causes glandular fever (infectious mononucleosis – contagious disease) and is linked to
some cancers. Mainly infects at 2-4 YOA (asymptomatic – shows no symptoms) or 15 YOA (more severe) passed via
salivary transfer, after infection virus is latent and remains in host for the rest of their life.
EBV first human tumour virus discovered in 1960s, was isolated in a lab
EBV can either infect b cells causing Burkitt’s lymphoma and Hodgkin’s lymphoma or can infect epithelial cells
causing gastric adenocarcinoma and nasopharyngeal carcinoma (NPC).
NPC is prevalent in southeast Asia, undifferentiated NPC is 100% associated with virus infection, can be caused due
to dietary factors such as salted fish or phorbol ester (found in plants).
Usually, EBV remains dormant in tonsillar b cells, it expresses a restricted pattern of gene, and 9 latent gene products
are prod. - EBV nuclear antigens (EBNA) 1,2,3A,3B,3C & LP and latent membrane protein (LMP) 1,2a, & 2b. It also
expresses a number of latencies associated with gene transcripts including EBV-encoded RNAs (EBERs) and BARTs
(moicroRNAs).
Latent Membrane Protein 1 (LMP1)
LMP1 is an essential active tumour necrosis factor receptor (TNFR), it’s a
key regulator of the reprogramming of EBV-mediated glycolysis in NPC
cells. It virally mimics CD40- expressed on antigen presenting cells and is
needed for B cell activation and development of B cells. It lacks intrinsic
signalling activity – instead recruits downstream adaptor molecules to
regulate gene expression. LMP1 is essentially a viral oncoprotein.
LMP1 transforms Rat-1 fibroblast in vitro (labs) and it promotes colony
formation in soft agar. It also induces EMT in certain cell lines – MDCK epithelial cells.
LMP1 structure; has 6 transmembrane pass protein with a long cytoplasmic tail with two signalling
domains and C terminal activation regions CTAR 2 and 1. Mutant versions of this protein is then
overexpressed in cells. Wild-type LMP1 structure is derived from a strain of EBV from IM patient. Three
mutants are created:
AAA (instead of PxQxT motif)
378stop (truncated at aa 378)
AAA/378stop (both mutation)
Cell lines can be used to determine which CTAR region of LMP1 is required for different effects. LMP1 induces EMT in
certain cell lines.
Cell migration can also be measured using trans wells, cell suspension is placed in upper chamber, then migratory
cells pas through polycarbonate membrane and cling to bottom side. After removal of non-migratory cells migratory
cells are stained and quantified. LMP1 promotes cell migration and invasion.
Transforming Growth Factor Beta 1 (TGFb1)
TGFb superfamily of cytokines has TGFb1, 2, 3 etc. they regulate multiple processes, cell proliferation,
differentiation, migration and apoptosis and migration. It displays context-dependent roles in cancer in pre-
malignant cells, TGFb functions as tumour suppressor but in later stages of cancer TGFb promotes invasion and
metastasis.
Epstein-Barr Virus (EBV)
15-20% of cancer caused by infectious agents, 10-15% caused by virus infection.
EBV a gamma herpesvirus, causes glandular fever (infectious mononucleosis – contagious disease) and is linked to
some cancers. Mainly infects at 2-4 YOA (asymptomatic – shows no symptoms) or 15 YOA (more severe) passed via
salivary transfer, after infection virus is latent and remains in host for the rest of their life.
EBV first human tumour virus discovered in 1960s, was isolated in a lab
EBV can either infect b cells causing Burkitt’s lymphoma and Hodgkin’s lymphoma or can infect epithelial cells
causing gastric adenocarcinoma and nasopharyngeal carcinoma (NPC).
NPC is prevalent in southeast Asia, undifferentiated NPC is 100% associated with virus infection, can be caused due
to dietary factors such as salted fish or phorbol ester (found in plants).
Usually, EBV remains dormant in tonsillar b cells, it expresses a restricted pattern of gene, and 9 latent gene products
are prod. - EBV nuclear antigens (EBNA) 1,2,3A,3B,3C & LP and latent membrane protein (LMP) 1,2a, & 2b. It also
expresses a number of latencies associated with gene transcripts including EBV-encoded RNAs (EBERs) and BARTs
(moicroRNAs).
Latent Membrane Protein 1 (LMP1)
LMP1 is an essential active tumour necrosis factor receptor (TNFR), it’s a
key regulator of the reprogramming of EBV-mediated glycolysis in NPC
cells. It virally mimics CD40- expressed on antigen presenting cells and is
needed for B cell activation and development of B cells. It lacks intrinsic
signalling activity – instead recruits downstream adaptor molecules to
regulate gene expression. LMP1 is essentially a viral oncoprotein.
LMP1 transforms Rat-1 fibroblast in vitro (labs) and it promotes colony
formation in soft agar. It also induces EMT in certain cell lines – MDCK epithelial cells.
LMP1 structure; has 6 transmembrane pass protein with a long cytoplasmic tail with two signalling
domains and C terminal activation regions CTAR 2 and 1. Mutant versions of this protein is then
overexpressed in cells. Wild-type LMP1 structure is derived from a strain of EBV from IM patient. Three
mutants are created:
AAA (instead of PxQxT motif)
378stop (truncated at aa 378)
AAA/378stop (both mutation)
Cell lines can be used to determine which CTAR region of LMP1 is required for different effects. LMP1 induces EMT in
certain cell lines.
Cell migration can also be measured using trans wells, cell suspension is placed in upper chamber, then migratory
cells pas through polycarbonate membrane and cling to bottom side. After removal of non-migratory cells migratory
cells are stained and quantified. LMP1 promotes cell migration and invasion.
Transforming Growth Factor Beta 1 (TGFb1)
TGFb superfamily of cytokines has TGFb1, 2, 3 etc. they regulate multiple processes, cell proliferation,
differentiation, migration and apoptosis and migration. It displays context-dependent roles in cancer in pre-
malignant cells, TGFb functions as tumour suppressor but in later stages of cancer TGFb promotes invasion and
metastasis.
