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Paeoniflorin Potentiates the Inhibitory Effects of Erlotinib in Pancreatic Cancer Cell Lines by Reducing ErbB3 Phosphorylation

View Article: PubMed Central - PubMed

ABSTRACT

Blockade of the epidermal growth factor receptor (EGFR) by EGFR tyrosine kinase inhibitors is insufficient for effective anti-tumor activity because the reactivation of the ErbB3 signaling pathway significantly contributes to activating the consequent phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Combinatorial therapies including ErbB3 targeting may ameliorate tumor responses to anti-EGFR therapies. In the present study, we found that in BxPC-3 and L3.6pl cells, which highly expressed the ErbB3 receptor, significant reduction in cell viability, induction of apoptosis were observed when treated with a combination of erlotinib and PF compared to either agent alone. Moreover, in ErbB3-expressing BxPC-3, L3.6pl and S2VP10 cell lines, the inhibition of ErbB3/PI3K/Akt phosphorylation were observed when treated with PF. Most strikingly, both EGFR/MAPK/Erk and ErbB3/PI3K/Akt activitions were substantially suppressed when treated with the combination of PF and erlotinib. However, in the ErbB3-deficient cell line MIAPaCa-2, no such effects were observed with similar treatments. Most importantly, these in vitro results were replicated in nude mouse transplanted tumor models. Taken together, our findings show that PF enhances the effect of erlotinib in ErbB3-expressing pancreatic cancer cells by directly suppressing ErbB3 activation, and PF in combination with erlotinib is much more effective as an antitumor agent compared with either agent alone.

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Effects of PF and Erlotinib on High ErbB3-Expressing Pancreatic Cancer Cells.(A) BxPC-3 cells were exposed to serial concentrations of PF for 48 h. The half maximal (50%) inhibitory concentration (IC50) value for PF in the BxPC-3 cell line is shown as a reference. The inhibitory effect of the combination of PF (50 μmol/L) and erlotinib (5 μmol/L) in BxPC-3 (B) and L3.6pl cell lines (C) using Trypan Blue Exclusion (Left) and MTS assays (Right). There was a significant reduction in the colony formation in BxPC-3 and L3.6pl cells treated with the combination compared to cells treated with either drug alone (D). Apoptotic effects of PF (50 μmol/L), erlotinib (5 μmol/L) and a combination of PF (50 μmol/L) and erlotinib (5 μmol/L) using Annexin-V/PI method. There was a significant potentiation of apoptosis in BxPC-3 cells and L3.6pl cells treated with the combination compared to cells treated with either drug alone (E).
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f1: Effects of PF and Erlotinib on High ErbB3-Expressing Pancreatic Cancer Cells.(A) BxPC-3 cells were exposed to serial concentrations of PF for 48 h. The half maximal (50%) inhibitory concentration (IC50) value for PF in the BxPC-3 cell line is shown as a reference. The inhibitory effect of the combination of PF (50 μmol/L) and erlotinib (5 μmol/L) in BxPC-3 (B) and L3.6pl cell lines (C) using Trypan Blue Exclusion (Left) and MTS assays (Right). There was a significant reduction in the colony formation in BxPC-3 and L3.6pl cells treated with the combination compared to cells treated with either drug alone (D). Apoptotic effects of PF (50 μmol/L), erlotinib (5 μmol/L) and a combination of PF (50 μmol/L) and erlotinib (5 μmol/L) using Annexin-V/PI method. There was a significant potentiation of apoptosis in BxPC-3 cells and L3.6pl cells treated with the combination compared to cells treated with either drug alone (E).

Mentions: As the first step of our investigation, we assessed the effect of PF on the viability of high ErbB3-expressing human pancreatic cancer BxPC-3 and L3.6pl cells. Cells were treated with increasing concentrations of PF for 48 h and Trypan Blue Exclusion analysis was used to assess the effect of these treatments on cell viability, principally to determine the proportion of live and dead cells within the population. As shown in Fig. 1A, PF treatment resulted in a significant concentration-dependent decrease in the number of viable cells starting at a concentration of 50 μmol/L with an inhibition rate of 15.24% (P < 0.001). The half maximal (50%) inhibitory concentration (IC50) value for PF was 82.19 μmol/L in the BxPC-3 cell line. Different concentrations of erlotinib (2 μmol/L, 5 μmol/L, 10 μmol/L and 20 μmol/L) were examined in BxPC-3cell line, and the inhibition rates were found to be 20.18%, 38.73%, 53.44%, 65.50%, respectively. We further examined the inhibitory effect of the combination of PF (50 μmol/L) and erlotinib (5 μmol/L) on high ErbB3-expressing pancreatic cancer cell lines BxPC-3(Fig. 1B) and L3.6pl (Fig. 1C) using Trypan Blue Exclusion and MTS assays. Co-treatment with PF enhanced the ability of erlotinib to induce growth inhibition in BxPC-3 and L3.6pl cells.


Paeoniflorin Potentiates the Inhibitory Effects of Erlotinib in Pancreatic Cancer Cell Lines by Reducing ErbB3 Phosphorylation
Effects of PF and Erlotinib on High ErbB3-Expressing Pancreatic Cancer Cells.(A) BxPC-3 cells were exposed to serial concentrations of PF for 48 h. The half maximal (50%) inhibitory concentration (IC50) value for PF in the BxPC-3 cell line is shown as a reference. The inhibitory effect of the combination of PF (50 μmol/L) and erlotinib (5 μmol/L) in BxPC-3 (B) and L3.6pl cell lines (C) using Trypan Blue Exclusion (Left) and MTS assays (Right). There was a significant reduction in the colony formation in BxPC-3 and L3.6pl cells treated with the combination compared to cells treated with either drug alone (D). Apoptotic effects of PF (50 μmol/L), erlotinib (5 μmol/L) and a combination of PF (50 μmol/L) and erlotinib (5 μmol/L) using Annexin-V/PI method. There was a significant potentiation of apoptosis in BxPC-3 cells and L3.6pl cells treated with the combination compared to cells treated with either drug alone (E).
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Related In: Results  -  Collection

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f1: Effects of PF and Erlotinib on High ErbB3-Expressing Pancreatic Cancer Cells.(A) BxPC-3 cells were exposed to serial concentrations of PF for 48 h. The half maximal (50%) inhibitory concentration (IC50) value for PF in the BxPC-3 cell line is shown as a reference. The inhibitory effect of the combination of PF (50 μmol/L) and erlotinib (5 μmol/L) in BxPC-3 (B) and L3.6pl cell lines (C) using Trypan Blue Exclusion (Left) and MTS assays (Right). There was a significant reduction in the colony formation in BxPC-3 and L3.6pl cells treated with the combination compared to cells treated with either drug alone (D). Apoptotic effects of PF (50 μmol/L), erlotinib (5 μmol/L) and a combination of PF (50 μmol/L) and erlotinib (5 μmol/L) using Annexin-V/PI method. There was a significant potentiation of apoptosis in BxPC-3 cells and L3.6pl cells treated with the combination compared to cells treated with either drug alone (E).
Mentions: As the first step of our investigation, we assessed the effect of PF on the viability of high ErbB3-expressing human pancreatic cancer BxPC-3 and L3.6pl cells. Cells were treated with increasing concentrations of PF for 48 h and Trypan Blue Exclusion analysis was used to assess the effect of these treatments on cell viability, principally to determine the proportion of live and dead cells within the population. As shown in Fig. 1A, PF treatment resulted in a significant concentration-dependent decrease in the number of viable cells starting at a concentration of 50 μmol/L with an inhibition rate of 15.24% (P < 0.001). The half maximal (50%) inhibitory concentration (IC50) value for PF was 82.19 μmol/L in the BxPC-3 cell line. Different concentrations of erlotinib (2 μmol/L, 5 μmol/L, 10 μmol/L and 20 μmol/L) were examined in BxPC-3cell line, and the inhibition rates were found to be 20.18%, 38.73%, 53.44%, 65.50%, respectively. We further examined the inhibitory effect of the combination of PF (50 μmol/L) and erlotinib (5 μmol/L) on high ErbB3-expressing pancreatic cancer cell lines BxPC-3(Fig. 1B) and L3.6pl (Fig. 1C) using Trypan Blue Exclusion and MTS assays. Co-treatment with PF enhanced the ability of erlotinib to induce growth inhibition in BxPC-3 and L3.6pl cells.

View Article: PubMed Central - PubMed

ABSTRACT

Blockade of the epidermal growth factor receptor (EGFR) by EGFR tyrosine kinase inhibitors is insufficient for effective anti-tumor activity because the reactivation of the ErbB3 signaling pathway significantly contributes to activating the consequent phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Combinatorial therapies including ErbB3 targeting may ameliorate tumor responses to anti-EGFR therapies. In the present study, we found that in BxPC-3 and L3.6pl cells, which highly expressed the ErbB3 receptor, significant reduction in cell viability, induction of apoptosis were observed when treated with a combination of erlotinib and PF compared to either agent alone. Moreover, in ErbB3-expressing BxPC-3, L3.6pl and S2VP10 cell lines, the inhibition of ErbB3/PI3K/Akt phosphorylation were observed when treated with PF. Most strikingly, both EGFR/MAPK/Erk and ErbB3/PI3K/Akt activitions were substantially suppressed when treated with the combination of PF and erlotinib. However, in the ErbB3-deficient cell line MIAPaCa-2, no such effects were observed with similar treatments. Most importantly, these in vitro results were replicated in nude mouse transplanted tumor models. Taken together, our findings show that PF enhances the effect of erlotinib in ErbB3-expressing pancreatic cancer cells by directly suppressing ErbB3 activation, and PF in combination with erlotinib is much more effective as an antitumor agent compared with either agent alone.

No MeSH data available.


Related in: MedlinePlus