p.3
Tumor Suppressor Genes and Oncogenes
What role do proto-oncogenes play in the cell cycle?
Proto-oncogenes act as the 'gas pedal' that makes the cell cycle go forward.
p.2
DNA Viruses and Their Role in Cancer
What mnemonic can help remember the types of DNA viruses?
PARdon PaPA He Has POX: PAR (Parvoviruses), P (Papillomaviruses), P (Polyomaviruses), A (Adenoviruses), H (Hepadnaviruses), H (Herpesviruses), POX (Poxviruses).
p.3
Tumor Suppressor Genes and Oncogenes
What is the role of the pRB (retinoblastoma protein) in the cell cycle?
pRB is a well-known tumor suppressor gene that functions at the G1 checkpoint to inhibit cell cycle progression.
p.3
Tumor Suppressor Genes and Oncogenes
What is the function of the p53 gene?
The p53 gene inhibits cell cycle kinase and contributes to cell growth regulation.
p.4
Mechanisms of Oncogenesis
What happens when viral oncoproteins interact with tumor suppressor genes?
Apoptosis is inhibited, allowing the cell cycle to continue, leading to mutations and carcinogenesis.
p.4
Polyomavirus Characteristics and Pathology
What are the clinical implications of BK virus in renal transplant patients?
It can cause hemorrhagic cystitis and polyoma associative nephropathy, leading to graft rejection in 50% of cases.
p.7
Mechanisms of Oncogenesis
What factors contribute to HPV lesions becoming carcinogenic?
Presence of a high-risk virus, persistent infection, and the host immune system.
p.2
General Features of Oncogenic Viruses
How can viruses be classified?
Viruses can be classified as DNA or RNA, single-stranded or double-stranded, and enveloped or unenveloped.
p.5
Papillomavirus and Its Clinical Implications
What are the general characteristics of the Papillomaviridae virion?
Icosahedral, 55 nm, dsDNA, circular, naked (no envelope), replicates in the nucleus.
p.1
DNA Viruses and Their Role in Cancer
How do DNA viruses contribute to tumor formation?
DNA viruses produce proteins that disrupt cell growth via cellular tumor suppressor genes.
p.2
Cell Cycle Regulation and Viral Interference
What are the phases of the cell cycle?
G1 Phase (Doubling of cytoplasm), S Phase (Synthesis of DNA and chromosomes), G2 Phase (Assembly of components for cell division), M Phase (Mitosis).
p.1
RNA Viruses and Their Oncogenic Potential
What is the difference between highly oncogenic and weakly oncogenic RNA viruses?
Highly oncogenic RNA viruses directly transform host cells by having oncogenes at the cellular level, while weakly oncogenic RNA viruses use indirect mechanisms to alter the host's environment to be conducive to carcinogenesis.
p.4
Polyomavirus Characteristics and Pathology
What does the small t antigen of Polyomavirus SV40 target?
Protein Phosphatase 2A (PP2A).
p.7
Prevention and Vaccination Strategies Against HPV
What are the different types of HPV vaccines available?
Bivalent (HPV 16, 18), Quadrivalent (HPV 6, 11, 16, 18), and 9-valent (HPV 31, 35, 45, 52, 58, 6, 11, 16, 18).
p.5
Polyomavirus Characteristics and Pathology
What brain disorder is associated with the JC virus?
Progressive multifocal leukoencephalopathy.
p.5
Papillomavirus and Its Clinical Implications
How were polyomaviruses and papillomaviruses classified in the past?
They were both under the family Papovaviridae.
p.1
RNA Viruses and Their Oncogenic Potential
How do RNA viruses contribute to tumor formation?
RNA viruses push proto-oncogenes to become oncogenes, which can either directly transform host cells or alter the host's mechanisms to be conducive to carcinogenesis.
p.4
Mechanisms of Oncogenesis
What do oncoproteins produced by DNA viruses do?
They form complexes with normal cell proteins to alter function.
p.7
Prevention and Vaccination Strategies Against HPV
What is required for an HPV DNA test to be considered positive?
It must be positive for a specific type of HPV.
p.7
Mechanisms of Oncogenesis
How does the host immune system affect HPV infection?
Immunocompetent individuals can clear the virus on their own, making the infection self-limiting.
p.6
Papillomavirus and Its Clinical Implications
What percentage of cervical cancers are linked to HPV?
99% of cervical cancers are linked to HPV.
p.5
Polyomavirus Characteristics and Pathology
What is the significance of SV40 in relation to humans?
SV40 can cause carcinoma in humans and was unknowingly included in polio vaccines cultured in Rhesus monkeys in the 1960s.
p.2
Mechanisms of Oncogenesis
Why are animal viruses like Adenovirus and SV40 important in research?
They help understand how DNA viruses transform normal cells.
p.3
DNA Viruses and Their Role in Cancer
What mechanisms do DNA viruses use to inactivate tumor suppressor genes?
DNA viruses form complexes with tumor suppressor genes to produce DNA oncoproteins, causing the cell to lose its 'brakes' and leading to continuous cell division and tumor formation.
p.2
Cell Cycle Regulation and Viral Interference
What happens at the checkpoints in the cell cycle?
The cell cycle pauses to check if chromosomes are okay and if the right chromosomes and materials were produced. If errors are spotted, the cell will either undergo apoptosis or cellular changes.
p.2
Tumor Suppressor Genes and Oncogenes
What balance does a normal cell maintain to prevent oncogenesis?
A balance of proto-oncogenes and tumor suppressor genes.
p.3
Mechanisms of Oncogenesis
How do viruses evade the host immune system?
Viruses can modify the MHC of the host, restrict expression of viral genes, mutate viral antigens, inhibit antigen processing, and infect and suppress essential immune cells.
p.4
Polyomavirus Characteristics and Pathology
What is the seroprevalence of Polyomavirus antibodies in the population?
70-80% of the population have Polyomavirus antibodies.
p.7
Human Cancer Viruses and Their Etiology
Why is there a high incidence of HPV in immunocompromised patients?
Because their immune systems are less capable of clearing the virus.
p.6
Papillomavirus and Its Clinical Implications
What are the common risk factors for HPV-related anal cancer?
Being immunocompromised (e.g., HIV/AIDS) and male-male intercourse.
p.6
Papillomavirus and Its Clinical Implications
What percentage of anal cancers are linked to HPV?
80% of anal cancers are linked to HPV.
p.7
Human Cancer Viruses and Their Etiology
What are the two most common risk factors for anal cancer?
Immunocompromised patients and male-male intercourse.
p.5
Polyomavirus Characteristics and Pathology
What are the symptoms of progressive multifocal leukoencephalopathy in a patient with multiple sclerosis over time?
12 months: white plaques, paraplegia; 32 months: multiple focus, decreased cognition; 34 months: increased leukoencephalopathy, decreased speech; 35 months: blindness.
p.1
Human Cancer Viruses and Their Etiology
What percentage of cancers have a viral etiology?
15-20% of cancers have a viral etiology.
p.4
Tumor Suppressor Genes and Oncogenes
What is the role of p53 in normal cell function?
p53 stops the cell cycle if there are mutations in the cell, leading to apoptosis.
p.4
Polyomavirus Characteristics and Pathology
In which patients does Polyomavirus pathology typically occur?
Immunocompromised patients such as renal transplant patients, bone marrow transplant patients, patients with HIV, pregnant women, and older people.
p.6
Papillomavirus and Its Clinical Implications
Where does the replication and expression of early HPV genes occur?
In the stratum spinosum layer.
p.3
RNA Viruses and Their Oncogenic Potential
How can RNA viruses contribute to carcinogenesis?
RNA viruses can insert sequences that activate cellular oncogenes, leading to tumor growth.
p.3
Tumor Suppressor Genes and Oncogenes
What are some examples of proto-oncogenes involved with viruses?
Examples include src (tyrosine-specific kinase), sis (growth factor, mitogen), myc (nuclear transcription factor), and erB (mutated growth factor).
p.4
Polyomavirus Characteristics and Pathology
What are the species of Polyomavirus?
BK virus, JC virus, SV40.
p.6
Papillomavirus and Its Clinical Implications
What tumor suppressor genes do HPV proteins E6 and E7 interact with?
E6 interacts with p53 and E7 interacts with pRb.
p.6
Papillomavirus and Its Clinical Implications
What are the clinical lesions caused by HPV?
Cutaneous, epidermal, and mucosal lesions such as warts, papillomas, and carcinomas.
p.7
Prevention and Vaccination Strategies Against HPV
What is the recommended screening test for cervical cancer in women 20 years old and above?
Pap smear, recommended every 3 years.
p.5
Polyomavirus Characteristics and Pathology
What are the characteristics of Merkel cell carcinoma?
Neuroendocrine disorder, rare skin carcinoma, wart-like lesion with smooth edges and enlarged blood vessels.
p.1
Prevention and Vaccination Strategies Against HPV
Why is knowing the viral origin of cancer beneficial?
Knowing the viral origin allows us to take specific measures to stop cancer from happening, such as vaccines.
p.5
Papillomavirus and Its Clinical Implications
What is the difference between the Papillomaviridae and Polyomaviridae families?
Papillomaviridae and Polyomaviridae were separated into their own families, erasing the Papovaviridae family.
p.3
DNA Viruses and Their Role in Cancer
How do DNA viruses affect the pRB gene?
DNA viruses form a complex that stops the pRB gene from functioning, allowing the cell to bypass the G1 checkpoint and proceed to the synthesis phase, leading to tumor formation.
p.4
Mechanisms of Oncogenesis
What is a key difference between DNA viruses and RNA viruses in terms of oncogenes?
DNA viruses do not have normal homologs in cells, whereas RNA viruses have proto-oncogenes.
p.4
Polyomavirus Characteristics and Pathology
What are the general features of Polyomavirus?
Icosahedral, 45nm, naked, dsDNA, circular, with 2 proteins and no envelope.
p.6
Papillomavirus and Its Clinical Implications
How is HPV typically transmitted?
Through direct contact and microabrasions.
p.3
Tumor Suppressor Genes and Oncogenes
What is the function of tumor suppressor genes?
Tumor suppressor genes act as 'brakes' that stop the cell cycle at checkpoints.
p.2
RNA Viruses and Their Oncogenic Potential
Which RNA viruses are considered oncogenic?
Flaviviruses (HCV) and Retroviruses (HIV, HTLV).
p.1
Mechanisms of Oncogenesis
What is the role of human cancer viruses in tumor formation?
Human cancer viruses are initiators of tumor formation but are not sufficient to complete carcinogenesis.
p.3
Mechanisms of Oncogenesis
What factors contribute to carcinogenesis?
Carcinogenesis is multifactorial, involving chronicity of infection, viral evasion strategies, and the host's susceptibility to viral infections and oncogenesis.
p.4
Polyomavirus Characteristics and Pathology
What is the significance of the large T antigen in Polyomavirus SV40?
It targets p53 and pRb, inactivating their growth inhibitory properties to allow viral DNA replication.
p.6
Papillomavirus and Its Clinical Implications
What type of genome does the Human Papillomavirus (HPV) have?
HPV has a circular genome.
p.6
Papillomavirus and Its Clinical Implications
What percentage of mouth and throat cancers are associated with HPV?
25% of mouth and 35% of throat cancers.
p.2
DNA Viruses and Their Role in Cancer
What are the types of double-stranded enveloped DNA viruses?
Hepadnaviruses (HBV), Herpesviruses (EBV, Human Herpes Virus 8), and Poxviruses.
p.1
Mechanisms of Oncogenesis
What are the two main types of viruses involved in oncogenesis?
DNA viruses and RNA viruses.
p.1
General Features of Oncogenic Viruses
What are the two types of viral morphology?
Naked virus (nucleic acid and protein coat) and enveloped virus (naked virus with an additional envelope layer).
p.6
Papillomavirus and Its Clinical Implications
Which HPV protein is used in vaccines due to its high antigenicity?
L1, the major capsid protein.
p.7
Human Cancer Viruses and Their Etiology
What are the two most common risk factors for anal cancer?
Immunocompromised patients and male-male intercourse.
p.7
Prevention and Vaccination Strategies Against HPV
What is the purpose of the HPV vaccine?
To create antibodies and provide immunity against HPV, most effective if administered before infection.
p.6
Papillomavirus and Its Clinical Implications
What are the clinical implications of HPV types 6 and 11?
They cause genital infections, anogenital warts, and laryngeal papillomas.
p.2
DNA Viruses and Their Role in Cancer
Which double-stranded unenveloped DNA viruses are known to be oncogenic?
Papillomaviruses (Human Papillomavirus), Adenoviruses, and Polyomaviruses (BK, JC, SV40).
p.3
Mechanisms of Oncogenesis
What occurs during carcinogenesis?
Carcinogenesis occurs during the activation of cellular oncogenes.
p.1
General Features of Oncogenic Viruses
What are the two properties of human cancer viruses?
1. Obligate intracellular parasites (no machinery to replicate on their own). 2. Tropism to certain cells.
p.3
Mechanisms of Oncogenesis
What is the difference between permissive and nonpermissive cells in the context of viral infections?
Permissive cells support the growth and replication of the virus, leading to cell lysis, while nonpermissive cells cannot support viral replication and are transformed into tumor cells.
p.7
Human Cancer Viruses and Their Etiology
At what age does the incidence of HPV infection peak?
Around age 15, when females typically become sexually active.
p.7
Prevention and Vaccination Strategies Against HPV
Why is HPV not tested in people under 20 years old?
Because most likely the virus has been cleared by the immune system.
