Novak’s gynecology 6Novak’s gynecology 6

Molecular Biology and Molecular Biology and GeneticsGenetics

부산백병원 산부인과부산백병원 산부인과R3 R3 박영미박영미

• Cell Cycle

• Modulation of Cell Growth and Function

• Immunology

• Factors that Trigger Neoplasia

  Cell CycleCell Cycle

Normal cell cycleNormal cell cycle

• Phases of cell cycle : G1, S, G2, M

• Duration of cell cycle : about 24hrs. – Variations in cell cycle time : different durations of the G1

• Three subpopulations of cells– Terminally differentiated cells

• RBC, Striated muscle cells, uterine smooth muscle cells

– Quiescent cells (G0)• fibroblasts

– Dividing cells • GI tract, skin, cervix

Normal cell cycleNormal cell cycle

• G1 Phase– Synthesis of enzymes & regulatory proteins

necessary for DNA synthesis– Duration (8 ~ 100 hrs)

• S Phase– Nuclear DNA content of the cell is copied.

Normal cell cycleNormal cell cycle

• G2 Phase– RNA & Protein synthesis– Repair of errors of DNA replication

• M Phase– Nuclear division occurs

Normal cell cycleNormal cell cycle

Genetic Control of the Cell Genetic Control of the Cell Cycle Cycle

• To successfully complete the cell cycle, a number of cell-division-cycle(cdc) genes are activated

• Two checkpoints– G1/S boundary : cell commits to proliferation – G2/M boundary : repair of any DNA damage must be completed

Genetic Control of the Cell Genetic Control of the Cell Cycle Cycle

• Cell Division Cycle Genes

– Factors that regulate the cell cycle checkpoints : • proteins encoded by the cdc2 family of genes• cyclin proteins

– Cyclins• Regulate the checkpoint at the G1/S boundary• Inhibit progression through the cell cycle in the presence of D

NA damage

Genetic Control of the Cell Genetic Control of the Cell Cycle Cycle

• Cell Division Cycle Genes

– The p53 tumor suppressor gene : • participate in delay of the cell cycle in order for DNA repair to

be completed

– Mitosis is initiated by activation of the cdc2 gene at the G2/M checkpoint.

• MPF (mitosis promoting factor) : p34 cdc2 protein, specific cyclins : catalyzes protein phosphorylation & drives the cell into mitosis

Genetic Control of the Cell Genetic Control of the Cell CycleCycle

• Apoptosis

– The regulation & maintenance of normal tissue mass requires a balance between cell proliferation & programmed cell death, or apoptosis

– Example• Deletion of the interdigital webs • Palatal fusion • Development of the intestinal mucosa • During the menstrual cycle : reduction in the number of endo

metrial cells. • Follicular atresia

Genetic Control of the Cell Genetic Control of the Cell CycleCycle

• Apoptosis

– Characteristics • Histological : cellular condensation & fragmentation of the nucleus • Biochemical : increase in transglutaminase expression & fluxes in intracellular calcium concentration • Molecular : complex interactions between the bcl-2, c- myc, p53, ced-9

Modulation of Cell Growth Modulation of Cell Growth and Function and Function

Oncogenes & Tumor Suppressor GenesOncogenes & Tumor Suppressor Genes

• Among the genes that participate in cell growth and function, proto-oncogenes & tumor suppressor genes are particularly important

• Proto-oncogenes – Encode : growth factors, membrane & cytoplasmic receptors, proteins that play key roles in the intracellular signal transduction cascade, nuclear DNA binding proteins – Positive effects upon cellular proliferation

• Tumor suppressor genes : – inhibitory regulatory effects on cellular proliferation

Oncogenes & Tumor Suppressor GenesOncogenes & Tumor Suppressor Genes

Steroid Hormones Steroid Hormones

• Estrogen

– diffuses through the cell membrane– binds to estrogen receptors that are located in the nuc

leus – the receptor-steroid complex binds to the DNA at spec

ific sequences, estrogen response elements (EREs) – gene expression, protein synthesis

Steroid HormonesSteroid Hormones

• Mutations of hormone receptors

– Absence of E2R-a in a male human• Incomplete epiphyseal closure• Increased bone turnover• Tall stature• Impaired glucose tolerance

– Mutations of the androgen receptor• Androgen insensitivity syndrome

Growth Factors Growth Factors

• Growth factors exert positive or negative effects upon the cell cycle by influencing gene expression related to events that occur at the G1/S cell cycle boundary

• Because of their short half-life in the extracellular space, growth factors generally act over limited distances through autocrine or paracrine mechanisms.

• The regulation of ovarian function occurs through autocrine, paracrine, and endocrine mechanisms.

Growth FactorsGrowth Factors

• The growth & differentiation of ovarian cells : influenced by the IGFs (insulin-like growth factors) * IGF-1 --> granulosa cell

: increase in cAMP, progesterone, oxytocin, proteoglycans,inhibin * IGF-1 --> theca cell

: increase in androgen production : theca cell --> TNF-a, EGF produce

* EGF : acts on granulosa cells to stimulate mitogenesis

• Disruption of these autocrine and paracrine intraovarian pathways

-> polycystic ovarian disease and disorders of ovulation

Growth FactorsGrowth Factors

Intracellular Signal Intracellular Signal TransductionTransduction

Some Intracellular Signalling Proteins Act as MolecSome Intracellular Signalling Proteins Act as Molecular Switchular Switch

Ser/Thr kinaseSer/Thr kinase

Tyr kinaseTyr kinase

Large trimeric GTP binding protein (G protein)Large trimeric GTP binding protein (G protein)

Small monomeric GTPasesSmall monomeric GTPases

Intracellular Signal Intracellular Signal TransductionTransduction

• Gene Expression-> transmission of external signals -> transcription and translation of specific genes -> the structure, function, proliferation of the cell

• Genetic errors -> result in abnormal structure and function-> premalignant, malignant, benign neoplasm of the female genital tract

• Amplification

– An increase in the copy number of a gene

– Increasing the amount of template DNA

– common event in malignancies of the female genital tract

• Point mutations

– The codon sequence alteration

– Qualitatively altering the gene product

– Point mutations of the p53 • The most common genetic

mutation in solid tumors• In approximately 50% of ov

arian cancers and 30-40% of endometrial cancers

• Deletions and Rearrangements

– Gross changes in the DNA template

– Synthesis of a markedly altered protein product

ImmunologyImmunology

- Immunologic - Immunologic Mechanisms - Mechanisms -

  Adaptive immune response Adaptive immune response

• Humoral immune responses : production of antibodies : specific antigen-binding sites that react with foreign an

tigens

• Cellular immune responses : antigen-specific immune responses : mediated directly by activated immune cells

• 면역반응은 면역작용을 수행하는 기전이 세포에 의해서 나타나는지 단백질에 의해서 나타나는지에 따라 다시 세포매개성면역반응과 체액성면역반응으로 구분한다

• 세포매개성 면역반응

– cytotoxic T cell 이나 자연살해세포의 경우처럼 세포가 직접 항원을 제거하는 경우

– 문제가 있는 세포를 직접 파괴 함으로서 항원과 함께 문제가 된 세포를 죽이는 방법으로 , 주로 종양세포에 대한 면역반응이나 바이러스에 감염된 세포에 대한 면역반응에서 볼 수 있다

• 체액성 면역반응 – 항체나 보체처럼 체액이나 혈액에 녹아있는 물질 , 즉 세포와는

독립적으로 존재하는 단백질에 의하여 나타나는 면역반응 – 세포와는 독립적으로 항원과 반응하므로 , 세포와 연관되어 있지

않는 세균 등과 같은 항원에 대한 면역반응에서 볼 수 있다

B Cells, Humoral Immunity, and Monoclonal B Cells, Humoral Immunity, and Monoclonal AntibodiesAntibodies

• B lymphocytes : the cells that synthesize and secrete antibodies

• Bone marrow stem cell -> Pre-B cell -> B cell -> plasma cell : produce antibodies

• Monoclonal antibodies – react with tumor-associated antigens – Immunotoxin-conjugated monoclonal antibodies

• directed to human ovarian adenocarcinoma antigens

T Lymphocytes and Cellular T Lymphocytes and Cellular Immunity Immunity

• T lymphocytes : acting as helper cells in both humoral & cellular respo

nses : acting as effector cells in cellular responses

• T cells can respond to antigens -> when these antigens are presented in association with MHC molecules on antigen-presenting cells.

T Lymphocytes and Cellular T Lymphocytes and Cellular ImmunityImmunity

• Two major subsets of mature T cells

– T helper/inducer cells : express the CD4 cell surface marker

– T suppressor/cytotoxic cells : express the CD8 cell surface marker

Monocytes and Macrophages Monocytes and Macrophages

• Myeloid cell

• Important roles in both innate and adaptive immune responses

• Macrophages– express MHC class II molecules – effective antigen-presenting cells for CD4 T cells– ingesting and killing microorganisms– cytotoxic, antitumor killer cell

Natural Killer cellsNatural Killer cells

• Nonspecific killing of tumor cells and virus-infected cells

• Innate form of immunity that does not require

an adaptive, memory response

• But the anti-tumor activity can be increased by exposure to several agents

Cytokines, Lymphokines, and Immune MediaCytokines, Lymphokines, and Immune Mediatorstors

• Cytokines called

– Monokines if they are derived from monocytes

– Lymphokines if they are derived from lymphocytes

– Interleukins if they exert actions on leukocytes

– Interferons if they have antiviral effects

- Interleukins - • IL-1

– Involved in fever & inflammatory responses

– Source : macrophages, phagocytic cells of the liver & spleen, s

ome B cells, epithelial cells, certain brain cells, the cells lining the synovial spaces

– Initiation of early events in immune responses

– Act as a B-cell activation-inducing factor

• IL-2

– T-cell growth factor

– Proliferation-inducing effects

– Source : activated T cells

• IL-3 – Increase the early differentiation of hematopoietic cell

s

• IL-4, IL-5, IL-6 – B-cell stimulating factor

• IL-6– Induction of cytotoxic T-lymphocyte differentiation

– Induction of acute phase reactant production by hepatocytes

– Activity as a colony-stimulating factor for hematopoietic stem cell

• IL-8, IL-10 – cytokine synthesis inhibitory factor

- Interferons -

• Three types : IFN-a, IFN-b, IFN-r --> interfere with viral production in infected cells --> direct antitumor effects

Factors that Trigger Neoplasia Factors that Trigger Neoplasia

Advanced Age Advanced Age

• Single most important risk factor

• Cancer Dx : 50 % of the population by 75 years of age

• Accumulation of critical genetic mutations over time

• Exposure to exogenous mutagens, altered host immune function

Environmental Factors Environmental Factors

• Smoking

– The best known example of mutagen exposure that is associated with the development of lung cancer

– Cigarette smoking and cervical ca. is associated

– Exposure of the transformation zone to cigarette smoke mutagens increase the DNA damage and cellular transformation

Environmental FactorsEnvironmental Factors

• Radiation

– Radiation induced cancer : the result of DNA damage that is not repaired

– Radiation induced cancer is approximately 10% greater in women than in men

: gender specific cancer, including breast cancer

– Radiation therapy for cervical cancer is associated with a small increase in the risk of colon cancer and thyroid cancer

Immune Function Immune Function

• Immunosuppressed renal transplant patients -> 40-fold increased risk of cervical cancer

• HIV-infected patients with depressed CD4 cell count -> increased risk of cervical dysplasia, invasive disease

• High dose chemotherapy with stem cell support -> increased risk of developing a variety of solid neoplasms

Diet Diet

• Dietary fat -> risk of colon & breast cancer

• Deficiency of folic acid & vitamin A & C -> cervical dysplasia & cervical cancer