Extracellular zinc stimulates ERK‐dependent activation of p21^Cip/WAF1 and inhibits proliferation of colorectal cancer cells

Abstract

1 Zinc is an important trace element in the body and is involved in both the proliferation and growth arrest of many kinds of cells including colorectal epithelial cells. The aim of this study was to identify the molecular mechanism of the growth regulation of colorectal cancer cells by extracellular zinc. 2 Zinc-stimulated activation of the mitogen-activated protein kinase (MAPK) cascade was measured by immunoblotting and Elk-1 dependent trans-reporter gene expression, and zincstimulated p21 Cip/WAF1 activation by immunoblotting, Northern blot analysis and immunochemistry. Cell proliferation was measured by thymidine and bromodeoxyuridine (BrdU) incorporation. 3 By treating colorectal cancer cells with 100 mM ZnCl 2 , MAPKs were activated in two di erent phases, the initial weak activation occurred within 5 min and this was followed by a stronger and more prolonged activation. 4 Zinc concomitantly activated Raf-1-MEK-MAPK kinases, and induced Elk-1 dependent transreporter gene expression. 5 Prolonged activation of MAPKs by 100 mM of ZnCl 2 resulted in the induction and nuclear localization of p21 Cip/WAF1 and was related to the inhibition of both thymidine and BrdU incorporations. 6 These results not only suggest the presence of a mechanism for p21 Cip/WAF1 dependent negative regulation of colorectal cancer cell growth by zinc but also suggest potential usage of zinc to control the growth of colorectal cancer cells.

p21Cip/WAF1 activation is an important factor for the ERK pathway dependent anti-proliferation of colorectal cancer cells

“…p53-independent induction of p21 Cip/W AF1 is acquired by activation of the ERK pathway involving activation of the Raf-1-MEK-ERK cascade (Liu et al, 1996;Sewing et al, 1997;Woods et al, 1997;Mahyar-Roemer and Roemer, 2001;Park et al, 2002). The inducers that can activate p21 Cip/W AF1 via activation of the ERK pathway include zinc , sulindac (Yip-Schneider and Schmidt, 2003), troglytazone (TRO) , calmodulin inhibitor W13 (Bosch et al, 1998), and butyrate (Archer et al, 1998;Derjuga et al, 2001).…”

“…The inducers that can activate p21 Cip/W AF1 via activation of the ERK pathway include zinc , sulindac (Yip-Schneider and Schmidt, 2003), troglytazone (TRO) , calmodulin inhibitor W13 (Bosch et al, 1998), and butyrate (Archer et al, 1998;Derjuga et al, 2001). The ERK pathway is involved in growth arrest (Liu et al, 1996;Sewing et al, 1997;Woods et al, 1997;Mahyar-Roemer and Roemer, 2001;Park et al, 2002;Boucher et al, 2004) as well as its well known function of growth stimulation (Blenis, 1993;Chang et al, 2003). Activation of p21 Cip/W AF1 , represented by induction and nuclear localization, is an important marker for anti-proliferation and growth arrest that occurs by prolonged activation of the ERK pathway (Nakano et al, 1997;Archer et al, 1998;Kim et al, 2002;Park et al, 2002;Eum et al, 2003).…”

“…The ERK pathway is involved in growth arrest (Liu et al, 1996;Sewing et al, 1997;Woods et al, 1997;Mahyar-Roemer and Roemer, 2001;Park et al, 2002;Boucher et al, 2004) as well as its well known function of growth stimulation (Blenis, 1993;Chang et al, 2003). Activation of p21 Cip/W AF1 , represented by induction and nuclear localization, is an important marker for anti-proliferation and growth arrest that occurs by prolonged activation of the ERK pathway (Nakano et al, 1997;Archer et al, 1998;Kim et al, 2002;Park et al, 2002;Eum et al, 2003). On the other hand, p21 Cip/WAF1 was not induced by the transient and weak ERK activation that is associated with proliferation (Sewing et al, 1997;Woods et al, 1997;Park et al, 2002).…”

“…Activation of p21 Cip/W AF1 , represented by induction and nuclear localization, is an important marker for anti-proliferation and growth arrest that occurs by prolonged activation of the ERK pathway (Nakano et al, 1997;Archer et al, 1998;Kim et al, 2002;Park et al, 2002;Eum et al, 2003). On the other hand, p21 Cip/WAF1 was not induced by the transient and weak ERK activation that is associated with proliferation (Sewing et al, 1997;Woods et al, 1997;Park et al, 2002). The differential activation of ERK that is related to different growth behaviors relies on signaling intensity and the serum concentration .…”

“…The differential activation of ERK that is related to different growth behaviors relies on signaling intensity and the serum concentration . Induction of p21 Cip/W AF1 is an important indicator for anti-proliferation in colorectal cancer cells (Nakano et al, 1997;Archer et al, 1998;Kim et al, 2002;Park et al, 2002). Percentages of cells incorporating BrdU w ere significantly reduced by zinc or TRO inducing p21 Cip/W AF1 Park et al, 2002).…”