ApoptosisNecrosis Apoptosis is a form of programmed cell death Apoptosis is responsible for the formation of digits in the developing mouse paw. Apoptotic cells are biochemically recognizable. Chapter 18

Programmed cell death removes unwanted cells during development. Apoptotic cells are biochemically recognizable. In apoptotic cells, phosphatidylserine flips from the inner leaflet to the outer and serves as an “eat me” signal to phagocytic cells. Apoptosis depends upon an intracellular proteolytic cascade that is mediated by caspases. The two best understood signaling pathways that can activate a caspase cascade are known as the extrinsic pathway and the intrinsic pathway. The intrinsic pathway is regulated by a set of pro- and anti- apoptotic proteins that are related to Bcl2. Either excessive or insufficient apoptosis can contribute to disease. ************** Apoptosis is a form of programmed cell death

Figure 18-5a Apoptosis depends upon an intracellular proteolytic cascade that is mediated by caspases. Caspase: They have a cysteine in their active site and cleave substrates at specific aspartic acid residues.

Figure 18-5b Apoptosis depends upon an intracellular proteolytic cascade that is mediated by caspases. Initiator Executioner Targets

Figure 18-8 The intrinsic pathway of apoptosis

Figure 18-7 Release of cytochrome c from mitochondria during apoptosis

Figure 18-8 The intrinsic pathway of apoptosis

Figure 18-9, 10 Pro-apoptotic Bcl2 proteins stimulate the release of mitochondrial intermembrane proteins

Figure 18-11a Molecular Biology of the Cell (© Garland Science 2008) The interplay between the pro- and anti-apoptotic Bcl2 proteins determines the activity of the intrinsic pathway

Figure 18-11b Molecular Biology of the Cell (© Garland Science 2008) The interplay between the pro- and anti-apoptotic Bcl2 proteins determines the activity of the intrinsic pathway

Figure Decreased apoptosis can contribute to tumorigenesis

Cancers are monoclonal in origin and multiple mutations are generally required for their progression. Tumor progression involves successive rounds of random inherited change followed by natural selection. A small population of cancer stem cells can be responsible for the maintenance of tumors. Tumor metastasis is a complex, multi-step process. Cancer-critical genes fall into two major classes: oncogenes and tumor suppressor genes. Cancer progression typically involves changes in both of these types of genes The Rb and p53 proteins are two of the most important tumor suppressor gene products for human cancer. ************** CANCER

Figure 20-6 Molecular Biology of the Cell (© Garland Science 2008) Cancers are generally monoclonal in origin Evidence from X-inactivation mosaics that demonstrates the monoclonal origin of cancers.

Figure 20-7 Molecular Biology of the Cell (© Garland Science 2008) Cancer incidence increases with age

Figure Molecular Biology of the Cell (© Garland Science 2008) Tumor progression involves successive rounds of random inherited change followed by natural selection

Figure Oncogene collaboration in mice: Further evidence for the requirement for multiple mutations during tumor formation

Figure Molecular Biology of the Cell (© Garland Science 2008) Cancers may arise from cancer stem cells

Fig Tumor metastasis is a complex multi-step process

Figure Molecular Biology of the Cell (© Garland Science 2008) An assay used to detect the presence of an oncogene: the loss of contact inhibition in culture

Figure Molecular Biology of the Cell (© Garland Science 2008) Some of the major pathway relevant to cancer in human cells

Figure 20-39a Molecular Biology of the Cell (© Garland Science 2008) Distinct pathways may mediate the disregulation of cell-cycle progression and the disregulation of cell growth in cancer cells

Figure Dominant & recessive mutations that contribute to cancer

Figure Molecular Biology of the Cell (© Garland Science 2008) The types of events that can make a proto-oncogene overactive and convert it into an oncogene.

Figure Chronic Myelogenous Leukemia (CML) & the Philadelphia chromosome Figure 20-5 (Hyperactive Abl)

Figure Molecular Biology of the Cell (© Garland Science 2008) Targeted therapy: the success of Gleevec Specifically targeting the Abl enzyme Binds to Abl in active site & “locks” the enzyme into an inactive state

Figure 20-52c Molecular Biology of the Cell (© Garland Science 2008) Targeted therapy: the success of Gleevec Specifically targeting the Abl enzyme

Figure Molecular Biology of the Cell (© Garland Science 2008) Multidrug Therapy: Combating Resistance

Figure Molecular Biology of the Cell (© Garland Science 2008) The genetic mechanisms that cause retinoblastoma

Figure Examples of the ways in which the one good copy of a tumor suppressor locus might be lost through change in DNA sequence,

Figure The loss of tumor suppression gene function can involve both genetic and epigenetic changes

Figure 20-38a A simplified view of the Rb pathway

Figure 20-38b,c Molecular Biology of the Cell (© Garland Science 2008) The Rb protein inhibits entry into the cell cycle

Figure Molecular Biology of the Cell (© Garland Science 2008) Mechanisms controlling cell-cycle entry and S-phase initiation in animal cells A central role for the Rb protein

Figure (part 1 of 3) Molecular Biology of the Cell (© Garland Science 2008)

Figure (part 2 of 3) Molecular Biology of the Cell (© Garland Science 2008)

Figure (part 3 of 3) Molecular Biology of the Cell (© Garland Science 2008) The inactivation of the Rb protein is needed for the entry into S-phase