Related Experiment Videos
Antitumor activity of combined blockade of epidermal growth factor receptor and protein kinase A
F Ciardiello1, V Damiano, R Bianco
1Dipartimento di Endocrinologia e Oncologia Molecolare e Clinica, Università degli Studi di Napoli Federico II, Naples, Italy.
Background:
Epidermal growth factor (EGF)-related proteins, such as transforming growth factor-alpha (TGF-alpha), control cancer cell growth through hormonal pathways (i.e., autocrine [hormone acts on cell that produces it] and paracrine [hormone acts on nearby cells] pathways). Overexpression of TGF-alpha and/or its receptor (EGFR) has been detected in human cancers. The blockade of EGFR activation by the use of anti-EGFR monoclonal antibodies (MAbs) has been proposed as a potential anticancer therapy. The type I cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKAI) is generally overexpressed in human cancer cells and is involved in neoplastic transformation. Inhibition of PKAI by selective cAMP analogues, such as 8-chloro-cAMP (8-CI-cAMP), induces growth inhibition in various human cancer cell lines.
Purpose:
On the basis of our previous observations of a cooperative anti-proliferative effect of anti-EGFR Mab 528 and 8-Cl-cAMP in human cancer cell lines in vitro, we evaluated the anticancer activity in vivo of the combination of an anti-EGFR MAb (MAb C225) and 8-Cl-cAMP.
Methods:
Athymic mice were injected subcutaneously with 10(7) human colon carcinoma GEO cells. After 7 days, when established tumor xenografts of 0.30-0.35 cm3 were detectable, 10-15 mice per group were treated intraperitoneally twice weekly with different doses of 8-Cl-cAMP and/or MAb C225. Cancer cell expression of various growth factors was evaluated by immunohistochemical analysis in tumors obtained from control and treated mice. Data were evaluated for statistical significance using the Student's t test and the Mantel-Cox logrank test. All P values represent two-sided tests of statistical significance.
Results:
A 5-week treatment with low doses of 8-Cl-cAMP (0.5 mg/dose) and MAb C225 (0.25 mg/dose) blocked GEO tumor growth (compared with that in control mice; P < .00001) and suppressed cancer cell production of autocrine growth factors, such as TGF-alpha, amphiregulin, and CRIPTO, and of angiogenic (promotes new blood vessel formation) factors, such as vascular endothelial growth factor and basic fibroblast growth factor, with no signs of toxicity. Control and 8-Cl-cAMP (0.5 mg/dose)-treated mice died within 9-10 weeks after tumor cell injection. In MAb C225 (0.25 mg/dose)-treated mice, GEO tumors resumed a growth rate comparable to that in control animals within 3 weeks following the end of treatment and the mice died between 11 and 20 weeks after tumor cell injection. GEO tumor growth was significantly delayed in the MAb C225 plus 8-Cl-cAMP treatment group (P < .00001) and was accompanied by a prolonged survival of mice (P < .00001) as compared with the control group.
Conclusions:
Long-term treatment with a combination of agents that selectively inhibit two intracellular signal-transduction enzymes, such as the PKAI serine-threonine kinase and the EGFR tyrosine kinase, has anticancer activity in vivo, reflected by suppression of tumor proliferation and angiogenesis, with no signs of toxicity.
Implications:
Since these inhibitors of intracellular mitogenic (growth-stimulating) signaling have a different mechanism(s) of action and do not antagonize the effects of cytotoxic therapy, a combination of anti-EGFR MAb C225 and 8-Cl-cAMP should be investigated as a nontoxic, long-term treatment for cancer patients following chemotherapy.
Insights
Combining anti-EGFR MAb C225 and 8-chloro-cAMP (8-Cl-cAMP) effectively inhibited human colon carcinoma GEO tumor growth in mice. This combination therapy demonstrated anticancer activity by suppressing tumor proliferation and angiogenesis with no observed toxicity.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Epidermal growth factor (EGF)-related proteins, like transforming growth factor-alpha (TGF-alpha), regulate cancer cell growth via autocrine and paracrine pathways.
- Overexpression of TGF-alpha and its receptor (EGFR) is common in human cancers, making EGFR a target for monoclonal antibody (MAb) therapy.
- Type I cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKAI) is overexpressed in cancer cells and implicated in neoplastic transformation; its inhibition by 8-chloro-cAMP (8-Cl-cAMP) has shown anti-proliferative effects.
Purpose of the Study:
- To evaluate the in vivo anticancer activity of combining an anti-EGFR MAb (MAb C225) with 8-Cl-cAMP.
- To build upon in vitro findings demonstrating a cooperative anti-proliferative effect between anti-EGFR MAb 528 and 8-Cl-cAMP.
Main Methods:
- Athymic mice bearing human colon carcinoma GEO xenografts were treated intraperitoneally with varying doses of 8-Cl-cAMP and/or MAb C225 twice weekly.
- Tumor growth was monitored, and immunohistochemical analysis was performed on tumors from control and treated groups to assess growth factor expression.
- Statistical significance was determined using Student's t test and the Mantel-Cox logrank test.
Main Results:
- Combined treatment with low doses of 8-Cl-cAMP (0.5 mg/dose) and MAb C225 (0.25 mg/dose) significantly blocked GEO tumor growth (P < .00001) and suppressed key growth and angiogenic factors.
- While 8-Cl-cAMP or MAb C225 monotherapy offered limited survival benefits, the combination therapy significantly delayed tumor growth and prolonged mouse survival (P < .00001) without observable toxicity.
- The combination therapy suppressed cancer cell production of autocrine growth factors (TGF-alpha, amphiregulin, CRIPTO) and angiogenic factors (VEGF, bFGF).
Conclusions:
- Long-term administration of agents targeting PKAI (via 8-Cl-cAMP) and EGFR (via MAb C225) exhibits significant in vivo anticancer activity.
- This combination therapy effectively suppresses tumor proliferation and angiogenesis with a favorable toxicity profile.
- The distinct mechanisms of action suggest that combining anti-EGFR MAb C225 and 8-Cl-cAMP warrants investigation as a non-toxic, long-term treatment option, potentially complementing chemotherapy.