Apoptosis

Apoptosis, the process of programmed cell death, is characterized by distinct morphology with DNA fragmentation and energy dependency [Elmore, 2007]. Apoptosis, also called “physiological cell death”, is involved in cell turnover, physiological involution, and atrophy of various tissues and organs [Kerr et al., 1972]. The formation of apoptotic bodies involves marked condensation of both nucleus and cytoplasm, nuclear fragmentation, and separation of protuberances [Kerr et al., 1972]. Apoptosis is characterized by DNA ladder and chromatin condensation. Several stimuli such as hypoxia, nucleotides deprivation, chemotherapeutical drugs, DNA damage, and mitotic spindle damage induce p53 activation, leading to p21 activation and cell cycle arrest [Pucci et al., 2000]. The SAHA or TSA treatment on neonatal human dermal fibroblasts (NHDFs) for 24 or 72 hrs inhibited proliferation of the NHDF cells [Glaser et al., 2003]. Considering that the acetylation of histone H4 was increased by the treatment of SAHA for 4 hrs, histone deacetylase inhibition may be involved in the inhibition of the cell proliferation [Glaser et al., 2003]. The impaired proliferation was observed in HDAC1^-/- ES cells, which was rescued with the reintroduction of HDAC1 [Zupkovitz et al., 2010]. An AOP focuses existes on p21 pathway leading to apoptosis, however, alternative pathways such as NF-kappaB signaling pathways may be involved in the apoptosis of spermatocytes [Wang et al., 2017].

Apoptosis is defined as a programmed cell death.  A decrease in apoptosis or a resistance to cell death is noted is described as a hallmark of cancer by Hanahan et al. It is widely admitted as an essential step in tumor proliferation (Adams, Lowe).  Apoptosis occurs after activation of a number of intrinsic and extrinsic signals which activate the protease caspase system which in turn activates the destruction of the cell.

The Bcl-2 is a protein family suppressing apoptosis by binding and inhibiting two proapoptotic proteins (Bax and Bak) and transferring them to the mitochondrial outer membrane. In the absence of inhibition by Bcl2, Bax and Bak destroy the mitochondrial membrane and releases proapoptotic signaling proteins, such as cytochrome c which activated the caspase system. An increased expression of these antiapoptotic proteins (Bcl-2, Bcl-x_L) occurs in cancer (Hanahan, Adams, Lowe). Several others pathways such as the loss of TP53 tumor suppressor function, or the increase of survival signals (Igf1/2), or decrease of proapoptotic factors (Bax, Bim, Puma) can also increase tumor growth (Hanahan, Juntilla).

In breast cancer a decrease in apoptosis and a resistance to cell death has been described thoroughly, especially using a dysregulation of the Bcl2 system or TP53 (Parton, Williams, Shahbandi).

Apoptosis is characterized by many morphological and biochemical changes such as homogenous condensation of chromatin to one side or the periphery of the nuclei, membrane blebbing and formation of apoptotic bodies with fragmented nuclei, DNA fragmentation, enzymatic activation of pro-caspases, or phosphatidylserine translocation that can be measured using electron and cytochemical optical microscopy, proteomic and genomic methods, and spectroscopic techniques [Archana et al., 2013; Martinez et al., 2010; Taatjes et al., 2008; Yasuhara et al., 2003].

・DNA fragmentation can be quantified with comet assay using electrophoresis, where the tail length, head size, tail intensity, and head intensity of the comet are measured [Yasuhara et al., 2003].

・The apoptosis is detected with the expression alteration of procaspases 7 and 3 by Western blotting using antibodies [Parajuli et al., 2014].

・The apoptosis is measured with down-regulation of anti-apoptotic gene baculoviral inhibitor of apoptosis protein repeat containing 2 (BIRC2, or cIAP1) [Parajuli et al., 2014].

・Apoptotic nucleosomes are detected using Cell Death Detection ELISA kit, which was calculated as absorbance subtraction at 405 nm and 490 nm [Parajuli et al., 2014].

・Cleavage of PARP is detected with Western blotting [Parajuli et al., 2014].

・Caspase-3 and caspase-9 activity is measured with the enzyme-catalyzed release of p-nitroanilide (pNA) and quantified at 405 nm [Wu et al., 2016].

・Apoptosis is measured with Annexin V-FITC probes, and the relative percentage of Annexin V-FITC-positive/PI-negative cells is analyzed by flow cytometry [Wu et al., 2016].

・Apoptosis is detected with the Terminal dUTP Nick End-Labeling (TUNEL) method to assay the endonuclease cleavage products by enzymatically end-labeling the DNA strand breaks [Kressel and Groscurth, 1994].

・For the detection of apoptosis, the testes are fixed in neutral buffered formalin and embedded in paraffin. Germ cell death is visualized in testis sections by Terminal dUTP Nick End-Labeling (TUNEL) staining method [Wade et al., 2008]. The incidence of TUNEL-positive cells is expressed as the number of positive cells per tubule examined for one entire testis section per animal [Wade et al., 2008]

・Apoptosis is induced in human prostate cancer cell lines (Homo sapiens) [Parajuli et al., 2014].

・Apoptosis occurs in B6C3F1 mouse (Mus musculus) [Elmore, 2007].

・Apoptosis occurs in Sprague-Dawley rat (Rattus norvegicus) [Elmore, 2007].

・Apoptosis occurs in the nematode (Caenorhabditis elegans) [Elmore, 2007].

• Apoptosis occurs in breast cancer cells, human and mouse (Parton)

Archana, M. et al. (2013), "Various methods available for detection of apoptotic cells", Indian J Cancer 50:274-283

Elmore, S. (2007), "Apoptosis: a review of programmed cell death", Toxicol Pathol 35:495-516

Glaser, K.B. et al. (2003), "Gene expression profiling of multiple histone deacetylase (HDAC) inhibitors: defining a common gene set produced by HDAC inhibition in T24 and MDA carcinoma cell lines", Mol Cancer Ther 2:151-163

Kerr, J.F.R. et al. (1972), "Apoptosis: a basic biological phenomenon with wide-ranging implications in tissue kinetics", Br J Cancer 26:239-257

Kressel, M. and Groscurth, P. (1994), "Distinction of apoptotic and necrotic cell death by in situ labelling of fragmented DNA", Cell Tissue Res 278:549-556

Martinez, M.M. et al. (2010), "Detection of apoptosis: A review of conventioinal and novel techniques", Anal Methods 2:996-1004

Parajuli, K.R. et al. (2014), "Methoxyacetic acid suppresses prostate cancer cell growth by inducing growth arrest and apoptosis", Am J Clin Exp Urol 2:300-313

Pucci, B. et al. (2000), "Cell cycle and apoptosis", Neoplasia 2:291-299

Taatjes, D.J. et al. (2008), "Morphological and cytochemical determination of cell death by apoptosis", Histochem Cell Biol 129:33-43

Wade, M.G. et al. (2008), "Methoxyacetic acid-induced spermatocyte death is associated with histone hyperacetylation in rats", Biol Reprod 78:822-831

Wang, C. et al. (2017), "CD147 regulates extrinsic apoptosis in spermatocytes by modulating NFkB signaling pathways", Oncotarget 8:3132-3143

Wu, R. et al. (2016), "microRNA-497 induces apoptosis and suppressed proliferation via the Bcl-2/Bax-caspase9-caspase 3 pathway and cyclin D2 protein in HUVECs", PLoS One 11:e0167052

Yasuhara, S. et al. (2003), "Comparison of comet assay, electron microscopy, and flow cytometry for detection of apoptosis", J Histochem Cytochem 51:873-885

Zupkovitz, G. et al. (2010), "The cyclin-dependent kinase inhibitor p21 is a crucial target for histone deacetylase 1 as a regulator of cellular proliferation", Mol Cell Biol 30:1171-1181

Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011 Mar 4;144(5):646-74. doi: 10.1016/j.cell.2011.02.013. PMID: 21376230

Adams JM, Cory S. The Bcl-2 apoptotic switch in cancer development and therapy. Oncogene. 2007 Feb 26;26(9):1324-37. doi: 10.1038/sj.onc.1210220. PMID: 17322918; PMCID: PMC2930981.

Lowe, S., Cepero, E. & Evan, G. Intrinsic tumour suppression. Nature 432, 307–315 (2004). https://doi.org/10.1038/nature03098

Parton M, Dowsett M, Smith I. Studies of apoptosis in breast cancer. BMJ. 2001 Jun 23;322(7301):1528-32. doi: 10.1136/bmj.322.7301.1528. PMID: 11420276; PMCID: PMC1120573.

Junttila MR, Evan GI. p53--a Jack of all trades but master of none. Nat Rev Cancer. 2009 Nov;9(11):821-9. doi: 10.1038/nrc2728. Epub 2009 Sep 24. PMID: 19776747.

Williams MM, Cook RS. Bcl-2 family proteins in breast development and cancer: could Mcl-1 targeting overcome therapeutic resistance? Oncotarget. 2015 Feb 28;6(6):3519-30. doi: 10.18632/oncotarget.2792. PMID: 25784482; PMCID: PMC4414133.

Shahbandi A, Nguyen HD, Jackson JG. TP53 Mutations and Outcomes in Breast Cancer: Reading beyond the Headlines. Trends Cancer. 2020 Feb;6(2):98-110. doi: 10.1016/j.trecan.2020.01.007. Epub 2020 Feb 5. PMID: 32061310; PMCID: PMC7931175.

Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011 Mar 4;144(5):646-74. doi: 10.1016/j.cell.2011.02.013. PMID: 21376230

Adams JM, Cory S. The Bcl-2 apoptotic switch in cancer development and therapy. Oncogene. 2007 Feb 26;26(9):1324-37. doi: 10.1038/sj.onc.1210220. PMID: 17322918; PMCID: PMC2930981.

Lowe, S., Cepero, E. & Evan, G. Intrinsic tumour suppression. Nature 432, 307–315 (2004). https://doi.org/10.1038/nature03098

Parton M, Dowsett M, Smith I. Studies of apoptosis in breast cancer. BMJ. 2001 Jun 23;322(7301):1528-32. doi: 10.1136/bmj.322.7301.1528. PMID: 11420276; PMCID: PMC1120573.

Junttila MR, Evan GI. p53--a Jack of all trades but master of none. Nat Rev Cancer. 2009 Nov;9(11):821-9. doi: 10.1038/nrc2728. Epub 2009 Sep 24. PMID: 19776747.

Williams MM, Cook RS. Bcl-2 family proteins in breast development and cancer: could Mcl-1 targeting overcome therapeutic resistance? Oncotarget. 2015 Feb 28;6(6):3519-30. doi: 10.18632/oncotarget.2792. PMID: 25784482; PMCID: PMC4414133.

Shahbandi A, Nguyen HD, Jackson JG. TP53 Mutations and Outcomes in Breast Cancer: Reading beyond the Headlines. Trends Cancer. 2020 Feb;6(2):98-110. doi: 10.1016/j.trecan.2020.01.007. Epub 2020 Feb 5. PMID: 32061310; PMCID: PMC7931175.

Parton M, Dowsett M, Smith I. Studies of apoptosis in breast cancer. BMJ. 2001 Jun 23;322(7301):1528-32. doi: 10.1136/bmj.322.7301.1528. PMID: 11420276; PMCID: PMC1120573.