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25-5
Cancer
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What is cancer?
Cancer is defined as the continuous uncontrolled growth of cells.
A tumor is a any abnormal proliferation of cells.
Benign tumors stays confined to its original location
Malignant tumors are capable of invading surrounding tissue or invading the entire body
Tumors are classified as to their cell type
Tumors can arise from any cell type in the body
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Cancer is an umbrella term covering a numerous conditions characterized by unscheduled and uncontrolled cellular proliferation
Almost any mammalian organ and cell type can succumb to cancer
The causes of cancer are many and varied, and include genetics, environmental influences, infectious agents and ageing. These transform normal cells into cancerous ones
The complexity of the disease that has hampered the development of effective and specific cancer therapies.
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Cancer cells have abnormal cell cycles
divide excessively and form tumors
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Breast cancer cell - altered morphology
Figure 8.10x1
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A kidney tumour
A kidney carcinoma (the blob at the top)
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Lung Cancer
x-ray
Squamous carcinoma
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Colon Cancer
X-ray
Gross
Microscopic
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9. Heterogeneous size and shape of cancer cells and cancer cell nuclei
Heterogeneous size and shape of cancer cells and cancer cell nuclei. The nuclear heterogeneity reflects the genetic instability.
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10. Cancer continued 3 cancer types
Carcinomas; constitute 90% of cancers, are cancers of epithelial cells
Sarcomas; are rare and consist of tumors of connective tissues (connective tissue, muscle, bone etc.)
Leukemias and lymphomas; constitute 8% of tumors. Sometimes referred to as liquid tumors. Leukemias arise from blood forming cells and lymphomas arise from cells of the immune system (T and B cells).
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11. Properties of cancer cells
Normal cells show
contact inhibition
Cancer cells lack
contact inhibition
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12. Properties of cancer cells
They keep growing
And growing
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13. Cancer Incidence and Death Rates
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Cancer
Cells in culture and in vivo exhibit contact-inhibition
Cancer cells lack contact inhibition feedback mechanisms. Clumps or foci develop.
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Cancer Grade
Alternate term “tumor grade”
Based on microscopic features (cytology or histology)
low grade moderate high
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16. Early detection is the key!
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17. What causes Cancer? Genetic mutations
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18. What is the source of oncogenes?
Mutation of a normal gene = change in DNA sequence
UV light, Xrays, natural or synthetic chemicals
Virus (ex. HPV and cervical cancer)
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19. How do normal cells become cancerous?
Selection within tumor for “most cancerous” cells
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Cancer: Benign
Benign: localized and of small size
Cells that closely resemble, and may function, like normal cells
May have a fibrous capsule around the cells
Become problems due to sheer bulk or due to secretions (e.g. hormones)
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Cancer : Malignant
Malignant tumors: high rate of division, properties may vary compared to cells of origin. Most malignant cells become metastatic
Invade surrounding tissue and establishment of secondary areas of growth: Metastasis
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Malignant tumors can invade other tissues and may kill the organism
Lymph vessels
Tumor
Glandular tissue
Metastasis 1
A tumor grows from a single cancer cell. 2
Cancer cells invade neighboring tissue. 3
Cancer cells spread through lymph and blood vessels to other parts of the body.
Figure 8.10
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Growth pattern
Benign Malignant
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25. Metastasis Carcinoma: derived from endoderm or ectoderm
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Events in Metastasis.
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Angiogenesis
Cancer cells block the formation of new blood vessels that bring necessary nutrients and oxygen to the hungry tumor cells
This forms a network of new blood vessels!
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24.1 Benign tumors arise with great frequency but pose little risk because they are localized and small
Figure 24-1
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24.1 Malignant tumors generally invade surrounding tissue and spread throughout the body
Alterations in cell-cell interactions and the formation of new blood vessels are
associated with malignancy
Figure 24-2
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30. DNA from tumor cells can transform normal cultured cells
transformed
Cells that continue to grow when normal cells have stopped are said to be transformed
Transformed cells may exhibit many of the properties of malignant tumor cells
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Figure 24-3