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62 Cards in this Set
- Front
- Back
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What are four chromosomal changes that occur in malignant cells?
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Deletions
Duplications Translocations Insertions |
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What are three new antigens expressed as a result of malignant transformation?
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Virus-encoded proteins
Modified preexisting cellular proteins Previously repressed cellular proteins |
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Wh do malignant cells appear rounded?
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Disaggregation of actin filaments and decreased adhesion to surface
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What term is applied to the disorganized, "piled-up" growth pattern of malignant cells?
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Loss of contact inhibition
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What term is applied to the infection of a cell by a tumor virus that enables it to continue growing past the lifetime of a normal cell?
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Immortalization
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What happens in regards to DNA synthesis when cells resting in the G0 phase are infected with a tumor virus?
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They enter the S phase and go on to divide
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Are the levels of cAMP increased or decreased in malignant cells?
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Decreased
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What is the phenomenon called whereby malignant cells have increased anaerobic glycolysis with increased lactic acid production?
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Warburg effect
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What are two models for viral tumorigenesis?
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Provirus model
Oncogene model |
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Which model explains viral tumorigenesis?
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Both proviruses and oncogenes may play a role in malignant transformation
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What is the provirus?
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Virion DNA is incorporated into host cell DNA seen with papillomavirus infection.
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What is the oncogene model?
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Activation of viral oncogenes leading to a malignant transformation.
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What are oncogenes?
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Genes encoding proteins involved in cellular growth which are present in oncogenic retroviruses
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What are two types of oncogenes?
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Cellular protooncogenes
Viral oncogenes |
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What is a difference between the cellular and viral oncogenes?
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Cellular protooncogenes have exons and introns
Viral oncogenes DO NOT have exons and introns |
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How are cellular oncogenes activated?
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Tumor viruses
Chemicals Radiation |
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How are viral oncogenes acquired?
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Cellular oncogenes are incorporated into retroviruses that carry the cellular oncogenes form one cell to another
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What are two functions of oncogenes?
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1) Encode a protein kinase that specifically phosphorylates tyrosine
2) Encode for cellular growth factors |
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What do growth factors act on?
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G proteins
Tyrosine kinases |
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How do the G proteins and tyrosine kinases affect DNA synthesis?
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They interact with cytoplasmic proteins that interact with the cell membrane or produce secondary messengers that are transported to the nucleus and interact with nuclear factors.
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What are three examples of oncogenes?
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ras gene
myc gene src gene |
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On what part of the cell does the ras oncogene have its effect?
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Cell membrane
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On what part of the cell does the myc oncogene have its effect?
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Nucleus
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How do tumor viruses of the retrovirus family that do not contain oncogenes cause malignant transformation?
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The DNA copy of the viral ribonucleic acid integrates near a cellular oncogene increasing its expression
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What is a tumor-suppressor gene?
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A gene encoding a protein product involved in the control of the cell cycle that, if mutated, can result in a malignant transformation, i.e., releasing the cells' "safety brake"
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Wht is the most studied tumor-suppressor gene?
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p53
Mutation of this tumor-suppressor gene has been found in malignant cells in more than half of all human cancers. |
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What is the function of a normal, nonmutated p53 gene?
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To encode a protein that promotes apoptosis of cells that have sustained DNA damage or that contain activated cellular oncogenes
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Why are tumor-suppressor genes considered recessive?
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They are considered recessive because two mutations are needed for crcinogenesis, i.e., the "two-hit model"
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What are four diseases caused by tumor-suppressor gene inactivation?
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Retinoblastoma
Wilms' Tumor Neurofibromatosis Li-Fraumeni syndrome These are all associated with inherited loss of the affected allele, also known as the "one-hit model" |
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What is vertical transmission?
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Tumor virus transmission involving movement of the virus from mother to offspring
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What are three ways by which vertical transmission occurs?
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1) Viral genetic material is present in the sperm and egg, i.e., prenatal
2) Virus is passed across the placenta, i.e., perinatal 3) Virus is transmitted in breast milk |
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How does the immune system respond to a virus transmitted by vertical transmission?
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The immune system does not eliminate the virus because it is exposed to it early in life and develops tolerance to the viral antigens
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What is horizontal transmission?
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Tumor virus transmission involving the passage of virus between animals that do not have a mother-offspring relationship
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What are nonpermissive cells?
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Cells that do not permit viral replication
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What are examples of nonpermissive cells?
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Rabbit cells do not replicate human T-cell leukemia virus (HTLV)
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What is required for malignant transformation in RNA and DNA tumor viruses?
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Viral gene expression
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Is replication of the viral genome required for malignant transformation?
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NO
only viral gene expression |
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What common intermediate do both DNA and RNA tumor viruses have?
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Double-stranded DNA intermediate
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What follows the production of the dsDNA intermediate?
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Integration into the host genome
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What are three important DNA tumor virus families?
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1) Papovaviruses, e.g., HPV
2) Herpesviruses, e.g., EBV and Kaposi sarcoma herpesvirus 3) Poxviruses, e.g., molluscum contagiosum virus |
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What is an important RNA tumor virus family?
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Retroviruses, e.g., HTLV
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What diseases are asociated with HTLV?
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Leukemia
Lymphoma |
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What diseases are asociated with HPV?
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Cervical cancer (types 16 and 18)
Plantar warts (types 1 and 4) Condyloma acuminatum and laryngeal papillomas (types 6 and 11) |
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What diseases are asociated with EBV?
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Burkitt's lymphoma
Nasopharyngeal carcinoma |
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What chromosome translocation occurs in Burkitt's lymphoma cells?
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8;14
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What cellular oncogene is juxtaposed to an active promoter as a result of hte 8;14 translocation in Burkitt's lymphoma
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c-myc
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What diseases are asociated with HBV?
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Primary hepatocellular carcinoma
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What diseases are asociated with HCV?
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Primary hepatocellular carcinoma
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What diseases are asociated with HHV-8
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kaposi sarcoma
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What type of a virus is HTLV-1?
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Retroviridae (+ssRNA)
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How is HTLV-1 transmitted?
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Sexual contact
Exchange of contaminated blood |
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What type of cancer has HTLV-1 been found to cause?
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Leukemia
T-cell lymphoma |
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How is the mechanism by which HTLV-1 causes cancer different from that of other retroviruses?
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It has no viral oncogene
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What type of T cells does HTLV-1 prefer to infect?
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CD4+
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What are the two unique HTLV-1 genes that play a role in oncogenesis?
How? |
tax and rex
By regulating messenger RNA transcription and translation |
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What are the two roles of the tax protein produced by HTLV-1?
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1) It acts on teh viral long terminal repeat (LTR) sequences to stimulate viral mRNA synthesis
2) It induces nuclear factor-kappa B (NF-kB), which stimulates the production of interleukin-2 (IL-2) and the IL-2 receptor |
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What is the role of the rex protein produced by HTLV-1?
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It determines which viral mRNAs can exit the nucleus and enter the cytoplasm to be translated
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What type of virus is HPV?
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Papovavirus (dsDNA)
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What types of epithelia does HPV infect?
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Keratinizing or mucosal squamous epithelia
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What does the term "papova" in papovaviruses represent?
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PApillomaviruses
POlyoma viruses VAcuolating viruses |
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How are papillomairuses classified?
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DNA nucleocapsid viruses with circular supercoiled dsDNA and an icosahedral nucleocapsid.
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What papovavirus causes progressive multifocal leukoencephalopathy?
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JC Virus
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