Induction of Apoptosis and Anoikis by Bit1 in Pancreatic Cancer Cells


Pancreatic cancer is a highly aggressive disease with a very high mortality rate among all human cancers. The poor prognosis is in part due to intrinsic resistance to the apoptosis-inducing effects of radio- and chemotherapy. To find alternative cell death pathways that can bypass the apoptotic resistance of pancreatic cancer cells, we examined the role of the novel anoikis effector Bit1 (Bcl-2 inhibitor of transcription) in the survival and apoptotic resistance of pancreatic cancer cells. Bit1 is a mitochondrial protein that induces a caspase-independent apoptosis upon its release into the cytosol following loss of integrin-mediated attachment to extracellular matrix (anoikis). In this report, we observed that ectopic expression of Bit1 in the cytosol reduced viability and induced caspase-independent apoptosis in human pancreatic cancer cell lines, Miapaca-2 and PANC-1. While increased expression of mitochondrial Bit1 in these cells did not induce apoptosis under attached conditions, detachment significantly induced higher level of apoptosis in mitochondrial Bit1-transfected cells than in control transfected cells. Conversely, downregulation of endogenous Bit1 in PANC-1 cells further enhanced their anoikis resistance. Furthermore, exogenous expression of mitochondrial Bit1 in Miapaca-2 cells inhibited their anchorage-independent growth and enhanced their sensitivity to etoposide-mediated apoptosis. Mechanistically, we found that the Bit1 apoptosis function is in part dependent on the groucho related Amino-terminal Enhancer of Split (AES) expression and is abrogated by the transcriptional corepressor TLE1 protein. Consistent with our in vitro findings that Bit1 is an effector of apoptosis in pancreatic tumor cells, we find that Bit1 is significantly downregulated in a fraction of advanced stages of human pancreatic carcinoma tissues. Taken together, these findings indicate that the Bit1-apoptotic pathway can be targeted to trigger cell death in pancreatic cancer cells and implicate Bit1 as a novel therapeutic agent in attenuating pancreatic chemoresistance.

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K. Leleux, T. Pham, M. Davis, P. Karmali and H. Biliran, "Induction of Apoptosis and Anoikis by Bit1 in Pancreatic Cancer Cells," Journal of Cancer Therapy, Vol. 4 No. 4, 2013, pp. 815-824. doi: 10.4236/jct.2013.44093.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] G. Schneider, J. T. Siveke, F. Eckel and R. M. Schmid, “Pancreatic Cancer Basic and Clinical Aspects,” Gastroenterology, Vol. 128, No. 6, 2005, pp. 1606-1625. doi:10.1053/j.gastro.2005.04.001
[2] A. Aghdassi, “Heat Shock Protein Increases Tumorigenicity and Inhibits Apoptosis in Pancreatic Adenocarcinoma,” Cancer Research, Vol. 67, 2007, pp. 616-625. doi:10.1158/0008-5472.CAN-06-1567
[3] P. Phillips, V. Dudeja, J. McCarroll, D. Borja-Cacho, R. Dawra, W. Grizzle, S. Vickers and A. Saluja, “Triptolide Induces Pancreatic Cancer Cell Death via Inhibition of Heat Shock Protein 70,” Cancer Research, Vol. 67, No. 19, 2007, pp. 9409-9416. doi:10.1158/0008-5472.CAN-07-1077
[4] A. Arlt, J. Vorndamm, M. Breitenbroich, U. Folsh, H. Kalthoff, W. Schmidt and H. Schafer, “Inhibition of NFkB Sensitizes Human Pancreatic Carcinoma Cells to Apoptosis Induced by Etoposide (VP16) or Doxorubicin,” Oncogene, Vol. 20, No. 7, 2001, pp. 859-868. doi:10.1038/sj.onc.1204168
[5] A. Arlt, A. Gehrz, S. Muerkoster, J. Vorndamm, M. Kruse, U. Folsch and H. Schafer, “Role of NF-kB and Akt/P13K in the Resistance of Pancreatic Carcinoma Cell Lines against Gemcitabine-Induced Cell Death,” Oncogene, Vol. 22, 2003, pp. 3243-3251. doi:10.1038/sj.onc.1206390
[6] S. Westphal and H. Kalthoff., “Apoptosis: Targets in Pancreatic Cancer,” Molecular Cancer, Vol. 2, 2003, p. 6. doi:10.1186/1476-4598-2-6
[7] P. Garcia-Morales, A. Gomez-Martinez, A. Carrato, I, Martinez-Lacaci, V. Barbea, J. Soto, E. Carrasco-Garcia, E., M. Menendez-Guterrez, M. Castro-Galache, J. Ferragut and M. Saceda, “Histone Deacetylase Inhibitors Induced Caspase-Independent Apoptosis in Human Pancreatic Adenocarcinoma Cell Lines,” Molecular Cancer Therapeutics, Vol. 4, No. 8, 2005, pp. 1222-1230. doi:10.1158/1535-7163.MCT-04-0186
[8] M. Parreno, I. Casanova, M. Cespedes, J. Vaque, M. Pavon, J. Leon and R. Mangues, “Bobel-24 and Derivatives Induce Caspase-Independent Death in Pancreatic Cancer Regardless of Apoptotic Resistance,” Cancer Research, Vol. 68, No. 15, 2008, pp. 6313-6323. doi:10.1158/0008-5472.CAN-08-1054
[9] Y. Jan, M. Matter, J. T. Pai, Y. L. Chen, J. Pilch, M. Komatsu, E. Ong, M. Fukuda and E. Ruoslahti, “A Mitochondrial Protein, Bit1, Mediates Apoptosis Regulared by Integrins and Groucho/TLE Corepressors,” Cell, Vol. 116, No. 5, 2004, pp. 751-762. doi:10.1016/S0092-8674(04)00204-1
[10] H. Biliran, Y. Jan, R. Chen, E. B. Pasquale and E. Ruoslahti, “Protein Kinase D is a Positive Regulator of Bit1 Apoptotic Function,” Journal of Biological Chemistry, Vol. 283, No. 42, 2008, pp. 28029-28037. doi:10.1074/jbc.M803139200
[11] C. Brunquell, H. Biliran, H. Tram, S. K. Ireland and E. Ruoslahti, “TLE1 Is an Anoikis Regulator and Is Downregulated by Bit1 in Breast Cancer Cells,” Molecular Cancer Research, Vol. 10, No. 11, 2012, pp. 1482-1495. doi:10.1158/1541-7786.MCR-12-0144
[12] P. P. Karmali, C. Brunquell, H. Tram, S. K. Ireland, E. Rouslahti and H. Biliran, “Metastasis of Tumor Cells Is Enhanced by Downregulation of Bit1,” PLoS One, Vol. 6, No. 8, 2011, Article ID: e23840. doi:10.1371/journal.pone.0023840
[13] H. Biliran, Y. Wang, S. Banerjee, H. Xu, H. Heng, A. Thakur, A. Bollig, F. H. Sarkar and J. D. Liao, “Overexpression of cyclin D1 Promotes Tumor Cell Growth and Confers Resistance to Cisplatin-Mediated Apoptosis in an Elastase-Myc Transgene-Expressing Pancreatic Tumor Cell Line,” Clinical Cancer Research, Vol. 11, No. 16, 2005, pp. 6075-6086. doi:10.1158/1078-0432.CCR-04-2419
[14] S. M. Frisch and H. Frances, “Disruption of Epithelial Cell-Matrix Interactions Induce Apoptosis,” Journal of Cell Biology, Vol. 124, No. 4, 1994, pp. 619-626. doi:10.1083/jcb.124.4.619
[15] S. M. Frisch and E. Ruoslahti, “Integrins and Anoikis,” Current Opinion in Cell Biology, Vol. 9, No. 5, 1997, pp. 701-706. doi:10.1016/S0955-0674(97)80124-X
[16] C. J. Yeo, R. A. Abrams, L. B, Grochow, T. A. Sohn, S. E. Ord, R. H. Hruban, M. L. Zahurak, W. C. Dooley, J. Coleman, P. K. Sauter, H. A. Pitt, K. D. Lillemoe and J. L. Cameron, “Pancreaticoduodenectomy for Pancreatic Adenocarcinoma: Postoperative Adjuvant CHemoradiation Improves Survival: A Prospective, Single-Institution Experience,” Annals of Surgery, Vol. 225, No. 5, 1997, pp. 621-636. doi:10.1097/00000658-199705000-00018
[17] M. Donadelli, C. Costanzo, S. Beghelli, et al., “Synergistic Inhibition of Pancreatic Adenocarcinoma Cell Growth by Trichostatin A and Gemcitabine,” Biochimica et Biophysica Acta, Vol. 1773, No. 7, 2007, pp. 1095-1106. doi:10.1016/j.bbamcr.2007.05.002

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