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Activation of PDGFr-β Signaling Pathway after Imatinib and Radioimmunotherapy Treatment in Experimental Pancreatic Cancer.

Abe M, Kortylewicz ZP, Enke CA, Mack E, Baranowska-Kortylewicz J - Cancers (Basel) (2011)

Bottom Line: Soon after treatment, levels of human PDGFr-β, compared to untreated tumors, are 3.4×, 12.4×, and 5.7× higher in imatinib-, radioimmunotherapy + imatinib-, and radioimmunotherapy-treated tumors, respectively.A continuous 14-day irradiation of imatinib-treated xenografts reduces levels of PDGFr-β and phosphorylated PDGFr-β by 5.3× and 4×, compared to earlier times.Human PDGF-B is upregulated suggesting that the survival signaling via the autocrine pathway is also triggered after stromal injury.

View Article: PubMed Central - PubMed

Affiliation: Minamata City Hospital and Medical Center, Minamata City, Kumamoto 867, Japan. jbaranow@unmc.edu.

ABSTRACT
Pancreatic cancer does not respond to a single-agent imatinib therapy. Consequently, multimodality treatments are contemplated. Published data indicate that in colorectal cancer, imatinib and radioimmunotherapy synergize to delay tumor growth. In pancreatic cancer, the tumor response is additive. This disparity of outcomes merited further studies because interactions between these modalities depend on the imatinib-induced reduction of the tumor interstitial fluid pressure. The examination of human and murine PDGFr-β/PDGF-B pathways in SW1990 pancreatic cancer xenografts revealed that the human branch is practically dormant in untreated tumors but the insult on the stromal component produces massive responses of human cancer cells. Inhibition of the stromal PDGFr-β with imatinib activates human PDGFr-β/PDGF-B signaling loop, silent in untreated xenografts, via an apparent paracrine rescue pathway. Responses are treatment- and time-dependent. Soon after treatment, levels of human PDGFr-β, compared to untreated tumors, are 3.4×, 12.4×, and 5.7× higher in imatinib-, radioimmunotherapy + imatinib-, and radioimmunotherapy-treated tumors, respectively. A continuous 14-day irradiation of imatinib-treated xenografts reduces levels of PDGFr-β and phosphorylated PDGFr-β by 5.3× and 4×, compared to earlier times. Human PDGF-B is upregulated suggesting that the survival signaling via the autocrine pathway is also triggered after stromal injury. These findings indicate that therapies targeting pancreatic cancer stromal components may have unintended mitogenic effects and that these effects can be reversed when imatinib is used in conjunction with radioimmunotherapy.

No MeSH data available.


Related in: MedlinePlus

Expression of PDGFr-β in SW1990 human pancreatic SW1990 adenocarcinoma xenografts grown subcutaneously in athymic mice. (a) Phosphorylated PDGFr-β of human and mouse origin. Western immunoblotting analyses of phosphorylated PDGFr-β with rabbit anti-human/anti-mouse phospho-PDGFr-β (Tyr751) polyclonal Ab3161 antibodies. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5. The bar graph represents protein band intensity normalized to the protein load as measured by the intensity of β-actin band using ImageJ. (b) Total PDGFr-β. Western immunoblotting analyses with rabbit anti-human/anti-mouse PDGFr-β polyclonal Ab3162 to determine the total expression of PDGFr-β in response to various treatments. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5 to determine total protein load per lane. The bar graph represents protein band intensity normalized using ImageJ to the protein load as measured by the intensity of β-actin band. Immunoblots for β-actin are identical in A and B because the same membrane was re-probed. Data for xenografts from control mice sham-treated with PBS are framed by the black rectangle.
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f2-cancers-03-02501: Expression of PDGFr-β in SW1990 human pancreatic SW1990 adenocarcinoma xenografts grown subcutaneously in athymic mice. (a) Phosphorylated PDGFr-β of human and mouse origin. Western immunoblotting analyses of phosphorylated PDGFr-β with rabbit anti-human/anti-mouse phospho-PDGFr-β (Tyr751) polyclonal Ab3161 antibodies. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5. The bar graph represents protein band intensity normalized to the protein load as measured by the intensity of β-actin band using ImageJ. (b) Total PDGFr-β. Western immunoblotting analyses with rabbit anti-human/anti-mouse PDGFr-β polyclonal Ab3162 to determine the total expression of PDGFr-β in response to various treatments. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5 to determine total protein load per lane. The bar graph represents protein band intensity normalized using ImageJ to the protein load as measured by the intensity of β-actin band. Immunoblots for β-actin are identical in A and B because the same membrane was re-probed. Data for xenografts from control mice sham-treated with PBS are framed by the black rectangle.

Mentions: Western immunoblotting analyses confirmed the ELISA findings (Figure 2 and Figure 3A). Phosphorylated PDGFr-β (Figure 2A) in PBS-treated tumors is barely detectable. All tumor samples collected on day five after treatment consistently follow the trends detected with the ELISA. Differences calculated from the protein band intensity are slightly more pronounced (Figure 2A, bar graph) compared to the results of ELISA probably because the threshold of the Western blot sensitivity is well beyond the sensitivity of the ELISA method. The specificity of reagents available for the immunoblotting of mouse PDGFr-β is not up to par with the ELISA's antibodies. For this reason, the Western blot shown in Figure 2B illustrates the total PDGFr-β expression, i.e., mouse and human PDGFr-β, as well as phosphorylated PDGFr-β of both origins. When the protein band intensity is calculated to account for the slight variations in the total protein applied (Figure 2B, bar graph), these results are practically indistinguishable from the ELISA data, i.e., the treatment has little or no effect on the expression of mouse PDGFr-β five days after treatment. In contrast, the expression of human PDGFr-β as detected by the immunoblotting is strongly dependent on the treatment and is perfectly comparable with the ELISA results (Figure 3A). The inclusion of either imatinib, 131ICC49, or both, in the SW1990 treatment stimulates human PDGFr-β expression well beyond the basal levels.


Activation of PDGFr-β Signaling Pathway after Imatinib and Radioimmunotherapy Treatment in Experimental Pancreatic Cancer.

Abe M, Kortylewicz ZP, Enke CA, Mack E, Baranowska-Kortylewicz J - Cancers (Basel) (2011)

Expression of PDGFr-β in SW1990 human pancreatic SW1990 adenocarcinoma xenografts grown subcutaneously in athymic mice. (a) Phosphorylated PDGFr-β of human and mouse origin. Western immunoblotting analyses of phosphorylated PDGFr-β with rabbit anti-human/anti-mouse phospho-PDGFr-β (Tyr751) polyclonal Ab3161 antibodies. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5. The bar graph represents protein band intensity normalized to the protein load as measured by the intensity of β-actin band using ImageJ. (b) Total PDGFr-β. Western immunoblotting analyses with rabbit anti-human/anti-mouse PDGFr-β polyclonal Ab3162 to determine the total expression of PDGFr-β in response to various treatments. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5 to determine total protein load per lane. The bar graph represents protein band intensity normalized using ImageJ to the protein load as measured by the intensity of β-actin band. Immunoblots for β-actin are identical in A and B because the same membrane was re-probed. Data for xenografts from control mice sham-treated with PBS are framed by the black rectangle.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3757429&req=5

f2-cancers-03-02501: Expression of PDGFr-β in SW1990 human pancreatic SW1990 adenocarcinoma xenografts grown subcutaneously in athymic mice. (a) Phosphorylated PDGFr-β of human and mouse origin. Western immunoblotting analyses of phosphorylated PDGFr-β with rabbit anti-human/anti-mouse phospho-PDGFr-β (Tyr751) polyclonal Ab3161 antibodies. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5. The bar graph represents protein band intensity normalized to the protein load as measured by the intensity of β-actin band using ImageJ. (b) Total PDGFr-β. Western immunoblotting analyses with rabbit anti-human/anti-mouse PDGFr-β polyclonal Ab3162 to determine the total expression of PDGFr-β in response to various treatments. The lower panel is the same membrane probed with rabbit anti-β-actin mAb 13E5 to determine total protein load per lane. The bar graph represents protein band intensity normalized using ImageJ to the protein load as measured by the intensity of β-actin band. Immunoblots for β-actin are identical in A and B because the same membrane was re-probed. Data for xenografts from control mice sham-treated with PBS are framed by the black rectangle.
Mentions: Western immunoblotting analyses confirmed the ELISA findings (Figure 2 and Figure 3A). Phosphorylated PDGFr-β (Figure 2A) in PBS-treated tumors is barely detectable. All tumor samples collected on day five after treatment consistently follow the trends detected with the ELISA. Differences calculated from the protein band intensity are slightly more pronounced (Figure 2A, bar graph) compared to the results of ELISA probably because the threshold of the Western blot sensitivity is well beyond the sensitivity of the ELISA method. The specificity of reagents available for the immunoblotting of mouse PDGFr-β is not up to par with the ELISA's antibodies. For this reason, the Western blot shown in Figure 2B illustrates the total PDGFr-β expression, i.e., mouse and human PDGFr-β, as well as phosphorylated PDGFr-β of both origins. When the protein band intensity is calculated to account for the slight variations in the total protein applied (Figure 2B, bar graph), these results are practically indistinguishable from the ELISA data, i.e., the treatment has little or no effect on the expression of mouse PDGFr-β five days after treatment. In contrast, the expression of human PDGFr-β as detected by the immunoblotting is strongly dependent on the treatment and is perfectly comparable with the ELISA results (Figure 3A). The inclusion of either imatinib, 131ICC49, or both, in the SW1990 treatment stimulates human PDGFr-β expression well beyond the basal levels.

Bottom Line: Soon after treatment, levels of human PDGFr-β, compared to untreated tumors, are 3.4×, 12.4×, and 5.7× higher in imatinib-, radioimmunotherapy + imatinib-, and radioimmunotherapy-treated tumors, respectively.A continuous 14-day irradiation of imatinib-treated xenografts reduces levels of PDGFr-β and phosphorylated PDGFr-β by 5.3× and 4×, compared to earlier times.Human PDGF-B is upregulated suggesting that the survival signaling via the autocrine pathway is also triggered after stromal injury.

View Article: PubMed Central - PubMed

Affiliation: Minamata City Hospital and Medical Center, Minamata City, Kumamoto 867, Japan. jbaranow@unmc.edu.

ABSTRACT
Pancreatic cancer does not respond to a single-agent imatinib therapy. Consequently, multimodality treatments are contemplated. Published data indicate that in colorectal cancer, imatinib and radioimmunotherapy synergize to delay tumor growth. In pancreatic cancer, the tumor response is additive. This disparity of outcomes merited further studies because interactions between these modalities depend on the imatinib-induced reduction of the tumor interstitial fluid pressure. The examination of human and murine PDGFr-β/PDGF-B pathways in SW1990 pancreatic cancer xenografts revealed that the human branch is practically dormant in untreated tumors but the insult on the stromal component produces massive responses of human cancer cells. Inhibition of the stromal PDGFr-β with imatinib activates human PDGFr-β/PDGF-B signaling loop, silent in untreated xenografts, via an apparent paracrine rescue pathway. Responses are treatment- and time-dependent. Soon after treatment, levels of human PDGFr-β, compared to untreated tumors, are 3.4×, 12.4×, and 5.7× higher in imatinib-, radioimmunotherapy + imatinib-, and radioimmunotherapy-treated tumors, respectively. A continuous 14-day irradiation of imatinib-treated xenografts reduces levels of PDGFr-β and phosphorylated PDGFr-β by 5.3× and 4×, compared to earlier times. Human PDGF-B is upregulated suggesting that the survival signaling via the autocrine pathway is also triggered after stromal injury. These findings indicate that therapies targeting pancreatic cancer stromal components may have unintended mitogenic effects and that these effects can be reversed when imatinib is used in conjunction with radioimmunotherapy.

No MeSH data available.


Related in: MedlinePlus