EGFR overexpression in canine primary lung cancer: pathogenetic implications and impact on survival

Investigating Cox-2 and EGFR as Biomarkers in Canine Oral Squamous Cell Carcinoma: Implications for Diagnosis and Therapy

Oral squamous cell carcinoma (OSCC) is a common and highly aggressive dog tumor known for its local invasiveness and metastatic potential. Understanding the molecular mechanisms driving the development and progression of OSCC is crucial for improving diagnostic and therapeutic strategies. Additionally, spontaneous oral squamous cell carcinomas in dogs are an excellent model for studying human counterparts. In this study, we aimed to investigate the significance of two key molecular components, Cox-2 and EGFR, in canine OSCC. We examined 34 tumor sections from various dog breeds to assess the immunoexpression of Cox-2 and EGFR. Our findings revealed that Cox-2 was highly expressed in 70.6% of cases, while EGFR overexpression was observed in 44.1%. Cox-2 overexpression showed association with histological grade of malignancy (HGM) (p = 0.006) and EGFR with vascular invasion (p = 0.006). COX-2 and EGFR concurrent expression was associated with HGM (p = 0.002), as well as with the presence of vascular invasion (p = 0.002). These data suggest that Cox-2 and EGFR could be promising biomarkers and potential therapeutic targets, opening avenues for developing novel treatment strategies for dogs affected by OSCC. Further studies are warranted to delve deeper into these findings and translate them into clinical practice.

Phenotypic and molecular characterization of novel pulmonary adenocarcinoma cell lines established from a dog

Canine pulmonary adenocarcinoma (PAC) resembles human lung tumors in never-smokers, but it is rarer than human pulmonary adenocarcinoma. Therefore, research on canine PAC is challenging. In the present study, we successfully established various novel canine PAC cell lines from a single lesion in a dog, including two parent cell lines and fourteen cloned cell lines, and characterized their cellular properties in vitro. Several of these cell lines showed epithelial-mesenchymal transition (EMT)-like and/or cancer stem cell (CSCs)-like phenotypes. We additionally assessed the sensitivity of the cells to vinorelbine in vitro. Three clonal lines, two of which showed EMT- and CSC-like phenotypes, were resistant to vinorelbine. Furthermore, we evaluated the expression and activation status of EGFR, HER2, and Ras signaling factors. The findings indicated that the cell lines we established preserved the expression and activation of these factors to varying extents. These novel canine PAC cell lines can be utilized in future research for understanding the pathogenesis and development of treatments for canine PAC.

Derivation of a new model of lung adenocarcinoma using canine lung cancer organoids for translational research in pulmonary medicine

Canine primary lung cancer (cPLC) is a rare malignant tumor in dogs, and exhibits poor prognosis. Effective therapeutic drugs against cPLC have not been established yet. Also, cPLC resembles human lung cancer in histopathological characteristics and gene expression profiles and thus could be an important research model for this disease. Three-dimensional organoid culture is known to recapitulate the tissue dynamics in vivo. We, therefore, tried to generate cPLC organoids (cPLCO) for analyzing the profiles of cPLC. After samples from cPLC and the corresponding normal lung tissue were collected, cPLCO were successfully generated, which recapitulated the tissue architecture of cPLC, expressed lung adenocarcinoma marker (TTF1), and exhibited tumorigenesis in vivo. The sensitivity of cPLCO to anti-cancer drugs was different among strains. RNA-sequencing analysis showed significantly upregulated 11 genes in cPLCO compared with canine normal lung organoids (cNLO). Moreover, cPLCO were enriched with the MEK-signaling pathway compared with cNLO. The MEK inhibitor, trametinib decreased the viability of several strains of cPLCO and inhibited the growth of cPLC xenografts. Collectively, our established cPLCO model might be a useful tool for identifying novel biomarkers for cPLC and a new research model for dog and human lung cancer.

Prognosis of primary pulmonary adenocarcinoma after surgical resection in small-breed dogs: 52 cases (2005-2021)

BACKGROUND

Tumor size is an important prognostic factor in lung cancer in dogs, and the canine lung carcinoma stage classification (CLCSC) recently has been proposed to subdivide tumor sizes. It is unclear if the same classification scheme can be used for small-breed dogs.

OBJECTIVES

To investigate whether the tumor size classification of CLCS is prognostic for survival and progression outcomes in small-breed dogs with surgically resected pulmonary adenocarcinomas (PACs).

ANIMALS

Fifty-two client-owned small-breed dogs with PAC.

METHODS

Single-center retrospective cohort study conducted between 2005 and 2021. Medical records of dogs weighing <15 kg with surgically resected lung masses histologically diagnosed as PAC were examined.

RESULTS

The numbers of dogs with tumor size ≤3 cm, >3 cm to ≤5 cm, >5 cm to ≤7 cm, or >7 cm were 15, 18, 14, and 5, respectively. The median progression-free interval (PFI) and overall survival time (OST) were 754 and 716 days, respectively. In univariable analysis, clinical signs, lymph node metastasis, margin, and histologic grade were associated with PFI, and age, clinical signs, margin, and lymph node metastasis were associated with OST. Tumor size classification of CLCS was associated with PFI in all categories, and tumor size >7 cm was associated with OST. In multivariable analysis, tumor size >5 cm to ≤7 cm and margin were associated with PFI, and age was associated with OST.

CONCLUSIONS AND CLINICAL IMPORTANCE

The tumor size classification of CLCS would be an important prognostic factor in small-breed dogs with surgically resected PACs.

Klinisch-pathologische Befunde, postoperative Überlebenszeiten und prognostische Faktoren bei Hunden mit primären Lungenkarzinomen

Einleitung Primäre Karzinome der Lunge (PLK) beim Hund sind selten, ihre Behandlung erfolgt chirurgisch. Ziel dieser Studie war die Untersuchung klinisch-pathologischer Befunde, postoperativer medianer Überlebenszeiten (mÜZ) und prognostischer Faktoren.

Material und Methoden Retrospektive Auswertung von 61 Hunden mit 62 PLK, die zwischen 2007 und 2017 chirurgisch behandelt wurden. Die statistische Auswertung erfolgte mittels Kaplan-Meier und Logrank Methoden.

Ergebnisse Von 62 PLKs lagen 35 (56 %) peripher im Lungenlappen, 21 (34 %) hilusnah und 6 (10 %) betrafen den gesamten Lungenlappen. In 49 Fällen lagen differenzierte Adenokarzinome vor; niedrig differenzierte bzw. anaplastische Karzinome (n = 10) und Plattenepithelkarzinome (n = 2) waren deutlich seltener. Eine Prädisposition für bestimmte Lungenlappen war nicht nachzuweisen. Dreizehn (21 %) Patienten zeigten keine und 10 (16 %) nur unspezifische, nicht auf den Respirationstrakt hinweisende Symptome. Insgesamt zeigten 48 (79 %) Hunde klinische Symptome wie Husten, Dyspnoe, Lethargie, Gewichtsverlust, Leistungsschwäche, Erbrechen und/oder Fieber. Die tracheobronchialen Lymphknoten (TBLN) waren in 9 von 51 untersuchten Fällen histologisch positiv für Metastasierung (N1) und negativ (N0) in 42 Fällen (nicht untersucht n = 10). Daten zum Langzeitverlauf waren für 50 Patienten verfügbar. Prognostisch relevante Variablen waren Lymphknotenmetastasierung in die TBLN (mÜZ: N1 41 Tage, N0 570 Tage; p < 0,01), Lungenmetastasen (mÜZ: M1 125 Tage, M0 630 Tage; p < 0,01), histologischer Subtyp (mÜZ: differenzierte Karzinome 620 Tage; andere Karzinome 135 Tage; p < 0,01), Tumordurchmesser größer als 3 cm (mÜZ < 3 cm 1155 Tage, ≥ 3 cm 330 Tage; p = 0,02) und Tumorlokalisation (mÜZ: hilusnah 330 Tage, peripher 650 Tage; p = 0,04).

Schlussfolgerung Beim PLK sind TBLN Status, Organmetastasen, Tumorlokalisation, histologischer Subtyp und Tumorgröße prognostisch relevante Kriterien. Hunde ohne prognostisch negative Faktoren können lange Überlebenszeiten aufweisen. In mehr als einem Drittel der Fälle bleiben die Tumoren asymptomatisch (21 %) bzw. ohne respirationstraktspezifische (16 %) Symptome.

Comparison of epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) immunohistochemical expression and outcomes in canine nasal carcinomas treated with radiation therapy

The expression of epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) has been reported in human nasopharyngeal and canine nasal carcinomas. The present study measured EGFR and COX-2 expression and calculated correlations between these proteins and clinical variables and outcomes in dogs with nasal carcinoma treated with radiation therapy. Before treatment, the immunohistochemistry of EGFR and COX-2 was performed in 67 biopsied tissues from canine nasal carcinomas. The correlations between these protein levels, clinical variables, and outcomes were evaluated. EGFR and COX-2 were detected in 88.1% and 82.1% of our samples, respectively. Neither EGFR nor COX-2 was associated with T stage and cribriform plate destruction. Dogs with low EGFR levels had a significantly longer survival time than dogs with high EGFR expression (P=0.043). The COX-2 expression level was not significantly associated with survival times after radiation therapy (P=0.653). Overexpression of EGFR is negatively correlated with survival in dogs with nasal carcinoma. Future studies should identify tumor biomarkers to develop therapeutic targets for effective treatments for canine nasal carcinomas.

Defucosylated Anti-Epidermal Growth Factor Receptor Monoclonal Antibody Exerted Antitumor Activities in Mouse Xenograft Models of Canine Mammary Gland Tumor

The epidermal growth factor receptor (EGFR) contributes to tumor malignancy through gene amplification and/or protein overexpression. In our previous study, we developed an anti-human EGFR (hEGFR) monoclonal antibody, clone EMab-134 (mouse IgG₁, kappa), which specifically detects both hEGFR and dog EGFR (dEGFR). The defucosylated mouse IgG_2a version of EMab-134 (134-mG_2a-f) exhibits antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) in dEGFR-overexpressed Chinese hamster ovary-K1 (CHO/dEGFR) cells and antitumor activities in mouse xenografts of CHO/dEGFR cells. In this study, the reactivity of 134-mG_2a-f against a canine mammary gland tumor cell line (SNP) was examined by flow cytometry and immunocytochemistry. Furthermore, 134-mG_2a-f highly exerted ADCC and CDC for SNP. The administration of 134-mG_2a-f significantly suppressed the SNP xenograft growth. These results suggest that 134-mG_2a-f exerts antitumor effects against dEGFR-expressing canine mammary gland tumors, and could be valuable as part of an antibody treatment regimen for them.

Defucosylated Mouse-Dog Chimeric Anti-EGFR Antibody Exerts Antitumor Activities in Mouse Xenograft Models of Canine Tumors

The epidermal growth factor receptor (EGFR) contributes to tumor malignancy via gene amplification and protein overexpression. Previously, we developed an anti-human EGFR (hEGFR) monoclonal antibody, namely EMab-134, which detects hEGFR and dog EGFR (dEGFR) with high sensitivity and specificity. In this study, we produced a defucosylated mouse–dog chimeric anti-EGFR monoclonal antibody, namely E134Bf. In vitro analysis revealed that E134Bf highly exerted antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity against a canine osteosarcoma cell line (D-17) and a canine fibroblastic cell line (A-72), both of which express endogenous dEGFR. Moreover, in vivo administration of E134Bf significantly suppressed the development of D-17 and A-72 compared with the control dog IgG in mouse xenografts. These results indicate that E134Bf exerts antitumor effects against dEGFR-expressing canine cancers and could be valuable as part of an antibody treatment regimen for dogs.

Defucosylated Anti-Epidermal Growth Factor Receptor Monoclonal Antibody 134-mG2a-f Exerts Antitumor Activities in Mouse Xenograft Models of Dog Epidermal Growth Factor Receptor-Overexpressed Cells

The epidermal growth factor receptor (EGFR) is a type I transmembrane protein, which is a member of the human epidermal growth factor receptor (HER) family of receptor tyrosine kinases. EGFR is a crucial mediator of cell growth and differentiation and forms homodimers or heterodimers with other HER family members to activate downstream signaling cascades. We previously established an anti-human EGFR (hEGFR) monoclonal antibody (mAb), clone EMab-134 (mouse IgG₁), by immunizing mice with the ectodomain of hEGFR. In this study, the subclass of EMab-134 was converted from IgG₁ to IgG_2a (134-mG_2a) and further defucosylated (134-mG_2a-f) to facilitate antibody-dependent cellular cytotoxicity (ADCC). Although 134-mG_2a-f was developed against hEGFR, it was shown to cross-react with dog EGFR (dEGFR) using flow cytometry. The dissociation constant (K_D) of 134-mG_2a-f against dEGFR-overexpressed CHO-K1 (CHO/dEGFR) cells was determined by flow cytometry to be 3.3 × 10^-9 M, indicating that 134-mG_2a-f possesses a high binding affinity to dEGFR. Analysis in vitro revealed that 134-mG_2a-f contributed to high levels of ADCC and complement-dependent cytotoxicity (CDC) in experiments targeting CHO/dEGFR cells. Furthermore, the in vivo administration of 134-mG_2a-f significantly inhibited the development of CHO/dEGFR in comparison with the results observed in response to control mouse IgG. Taken together, the findings of this study demonstrate that 134-mG_2a-f could be useful as part of a therapeutic regimen for dEGFR-expressing canine cancers.

Vaccine-induced ErbB (EGFR/HER2)-specific immunity in spontaneous canine cancer

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Spontaneous dog cancers closely resemble human cancer.

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Dogs with EGFR associated tumors were immunized with an EGFR/HER2 peptide vaccine.

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EGFR peptide vaccinated dogs developed anti-EGFR/HER2 antibodies.

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Vaccinated dogs have anti-EGFR antibody and T cells infiltrating tumors.

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Vaccinated dogs with osteosarcoma had tumor regression and increased survival.

Epidermal Growth Factor Receptor (EGFR) is overexpressed on a number of human cancers, and often is indicative of a poor outcome. Treatment of EGFR/HER2 overexpressing cancers includes monoclonal antibody therapy (cetuximab/trastuzumab) either alone or in conjunction with other standard cancer therapies. While monoclonal antibody therapy has been proven to be efficacious in the treatment of EGFR/HER2 overexpressing tumors, drawbacks include the lack of long-lasting immunity and acquired resistance to monoclonal therapy. An alternative approach is to induce a polyclonal anti-EGFR/HER2 tumor antigen response by vaccine therapy. In this phase I/II open-label study, we examined anti-tumor immunity in companion dogs with spontaneous EGFR expressing tumors. Canine cancers represent an outbred population in which the initiation, progression of disease, mutations and growth factors closely resemble that of human cancers. Dogs with EGFR expressing tumors were immunized with a short peptide of the EGFR extracellular domain with sequence homology to HER2. Serial serum analyses demonstrated high titers of EGFR/HER2 binding antibodies with biological activity similar to that of cetuximab and trastuzumab. Canine antibodies bound both canine and human EGFR on tumor cell lines and tumor tissue. CD8 T cells and IgG deposition were evident in tumors from immunized dogs. The antibodies inhibited EGFR intracellular signaling and inhibited tumor growth in vitro. Additionally, we illustrate objective responses in reducing tumors at metastatic sites in host animals. The data support the approach of amplifying anti-tumor immunity that may be relevant in combination with other immune modifying therapies such as checkpoint inhibitors.

Computed tomography radiomic features hold prognostic utility for canine lung tumors: An analytical study

Quantitative analysis of computed tomography (CT) radiomic features is an indirect measure of tumor heterogeneity, which has been associated with prognosis in human lung carcinoma. Canine lung tumors share similar features to human lung tumors and serve as a model in which to investigate the utility of radiomic features in differentiating tumor type and prognostication. The purpose of this study was to correlate first-order radiomic features from canine pulmonary tumors to histopathologic characteristics and outcome. Disease-free survival, overall survival time and tumor-specific survival were calculated as days from the date of CT scan. Sixty-seven tumors from 65 dogs were evaluated. Fifty-six tumors were classified as primary pulmonary adenocarcinomas and 11 were non-adenocarcinomas. All dogs were treated with surgical resection; 14 dogs received adjuvant chemotherapy. Second opinion histopathology in 63 tumors confirmed the histologic diagnosis in all dogs and further characterized 53 adenocarcinomas. The median overall survival time was longer (p = 0.004) for adenocarcinomas (339d) compared to non-adenocarcinomas (55d). There was wide variation in first-order radiomic statistics across tumors. Mean Hounsfield units (HU) ratio (p = 0.042) and median mean HU ratio (p = 0.042) were higher in adenocarcinomas than in non-adenocarcinomas. For dogs with adenocarcinoma, completeness of excision was associated with overall survival (p<0.001) while higher mitotic index (p = 0.007) and histologic score (p = 0.037) were associated with shorter disease-free survival. CT-derived tumor variables prognostic for outcome included volume, maximum axial diameter, and four radiomic features: integral total, integral total mean ratio, total HU, and max mean HU ratio. Tumor volume was also significantly associated with tumor invasion (p = 0.044). Further study of radiomic features in canine lung tumors is warranted as a method to non-invasively interrogate CT images for potential predictive and prognostic utility.

EGFR Overexpression and Sequence Analysis of KRAS, BRAF, and EGFR Mutation Hot Spots in Canine Intestinal Adenocarcinoma

Epidermal growth factor receptor (EGFR) is overexpressed in many human colorectal cancers and anti-EGFR agents are employed as immunotherapies. However, KRAS, EGFR, and BRAF gene mutations can influence the activity of the anti-EGFR agents. We evaluated EGFR expression at protein and mRNA levels in canine intestinal adenocarcinomas using immunohistochemistry (IHC) and RNA in situ hybridization (RNA-ISH). We also investigated the mutation status of EGFR, KRAS, and BRAF to aid the development of anti-EGFR agents for canine intestinal adenocarcinoma. EGFR expression was highest in adenocarcinoma, followed by intramucosal neoplasia (adenoma and in situ carcinoma), and nonneoplastic canine intestinal tissue, at both protein (P = .000) and mRNA (P = .005) levels. The EGFR, KRAS, and BRAF genes showed wild-type sequences at the mutation hot spots in all 13 specimens. Thus, EGFR might serve as a promising diagnostic marker in canine intestinal adenocarcinoma, and further studies would be needed to develop EGFR-targeted anticancer therapies.

A Contemporary Retrospective Study of Survival in Dogs With Primary Lung Tumors: 40 Cases (2005-2017)

Objective: To report the median survival time in a contemporary cohort of dogs with primary lung tumors and intrathoracic nodal metastasis.

Design: Retrospective Case Series.

Animals (or sample): Dogs with primary lung tumors treated with lung lobectomy and lymph node biopsy.

Procedures: The medical record database at Colorado State University was queried for dogs with primary lung tumors from January 1, 2005 to December 31, 2017. Patients were identified for inclusion if they had lung lobectomy and an intrathoracic lymph node biopsy performed. The median survival time (MST) for lymph node positive (LN+) and negative dogs (LN–) was calculated as well as the MST in dogs that did or did not receive adjuvant chemotherapy. Differences were compared between groups with significance set at p < 0.05.

Results: The MST in LN+ dogs (n = 11) was 167 days which was not statistically different from LN– dogs (n = 29) at 456 days (p = 0.2407). No significant difference in the MST in LN+ dogs was identified between dogs that received adjuvant chemotherapy (n = 4; 110 days) and those that did not receive adjuvant chemotherapy (n = 6; 125 days) (p = 0.4409). There was no difference in survival time in LN– dogs receiving chemotherapy (n = 12; 335 days) as compared to those LN– dogs (n = 10) that did not receive adjuvant chemotherapy (258.5 days; p = 0.6475).

Conclusions and Clinical Relevance: The survival of primary pulmonary neoplasia in dogs with intrathoracic nodal metastasis is longer than previously reported in this contemporary cohort. Chemotherapy did not appear to improve survival in LN+ or LN– dogs. The combination of tumor size between 100 and 999 cm³ and positive lymph node status significantly reduced survival.

Overexpression of human epidermal growth factor receptor 2 in canine primary lung cancer

Human epidermal growth factor receptor 2 (HER2) overexpression has been reported in various human cancers. HER2-targeted therapies showed clinical responses in humans with HER2-positive tumors. The incidence of canine primary lung cancer (cPLC) is increasing, but there are no effective systemic therapies for dogs with late-stage cPLC. HER2-targeted therapy could be an option for cPLC, but HER2 expression in cPLC remains unknown. We evaluated HER2 expression in cPLC. Immunohistochemical analysis revealed that 3 samples (19%) scored 3+; 8 (50%), 2+; 5 (31%); and 1+ and 0 (0%), 0. Of the cPLC tissues, 69% were HER2 positive (scored ≥2+). These data would lead to further evaluation of the role of HER2 in cPLC as a mechanism of malignancy and therapeutic target.

Elevated EGF Levels in the Blood Serum of Dogs with Periodontal Diseases and Oral Tumours

BACKGROUND/AIM

Paradontopathy and neoplasms of the oral cavity represent one of the greatest challenges in human and animal dentistry. EGF plays a key role in maintaining the integrity and proper rate of cell proliferation in normal oral epithelium. The aim of the present study was to study serum levels of EGF in dogs diagnosed with periodontal diseases and oral cavity tumours.

MATERIALS AND METHODS

The samples comprised of cancerous tissue sections and serum obtained from dogs of various breeds, aged between 5-13 years. Serum EGF concentrations were measured by an immunoenzymatic method.

RESULTS

The median for EGF concentration in serum of dogs suffered from severe periodontal diseases was greater when compared to the control group. EGF concentration in dogs with malignant tumours was significantly higher than in those with non-malignant growths. A positive correlation between EGF concentration and tumour size was also observed. EGF level in dogs diagnosed with benign tumours was comparable to the control group.

CONCLUSION

The blood serum level of EGF increases significantly in patients with malignant oral tumours and advanced periodontal disease. In malignant tumours, the high level of EGF correlates with the size and invasiveness of the neoplasm.

Antitumor activity of nimotuzumab in combination with cisplatin in lung cancer cell line A549 in vitro

Nimotuzumab, a humanized IgG1 monoclonal antibody against epidermal growth factor receptor (EGFR), increases radiosensitivity in lung cancer. Cisplatin is an effective antitumor agent in lung cancer. In the present study, the antitumor activity of nimotuzumab combined with cisplatin was investigated in A549 lung cancer cells. Viability, cell cycle distribution and cyclin D1 expression were assessed following treatment with nimotuzumab alone, cisplatin alone, nimotuzumab in combination with cisplatin, and nimotuzumab followed sequentially by cisplatin. The inhibitory effect on cell viability of nimotuzumab sequentially followed by cisplatin was higher compared with cisplatin alone (82.17±1.62 vs. 56.97±1.42%). Compared with treatment by cisplatin alone, cell cycle analysis by flow cytometry demonstrated that the percentage of cells in the G₀/G₁ phase was increased when A549 cells were treated with nimotuzumab followed sequentially by cisplatin (P<0.01). However, the proportion of cells in G₀/G₁ phase was decreased when A549 cells were treated with nimotuzumab and cisplatin simultaneously compared with cisplatin alone (P<0.05). Cyclin D1 expression was decreased in all chemotherapy treatment groups; the most significant decrease was in A549 cells treated with nimotuzumab followed sequentially by cisplatin. Nimotuzumab may enhance the antitumor activity of cisplatin on A549 cells. The cell cycle arrest at G₀/G₁ observed may have been due to decreased cyclin D1 levels. Potential antagonism was identified when A549 cells were treated with nimotuzumab and cisplatin simultaneously, indicating that targeted therapy may be more effective when administered prior to conventional chemotherapy.

Receptor tyrosine kinase expression and phosphorylation in canine nasal carcinoma

Preliminary studies have supported use of toceranib phosphate (Palladia®) in treatment of canine nasal carcinomas, though the mechanisms of its activity are unknown. This study evaluated sixteen canine nasal carcinoma and five normal nasal epithelium samples for expression and phosphorylation of known targets of toceranib [vascular endothelial growth factor receptor-2 (VEGR2), platelet derived growth factor alpha (PDGFR-α), platelet derived growth factor receptor beta (PDGFR-β), and stem cell factor receptor (c-KIT)] and epidermal growth factor receptor 1 (EGFR1) using immunohistochemistry, RT-PCR and a receptor tyrosine kinase (RTK) phosphorylation panel. Protein for VEGFR2 was expressed in all carcinomas, PDGFR-α was noted in 15/16, whereas PDGFR-β was detected in 3/16 samples, but showed significant stromal staining. Protein expression for c-KIT was present in 4/16 and EGFR1 was noted in 14/16 samples. Normal tissue showed variable protein expression of the RTKs. Messenger RNA for VEGFR2, PDGFR-β, and c-KIT were noted in all samples. Messenger RNA for PDGFR-α and EGFR1 were detected in 15/16 samples. All normal nasal tissue detected messenger RNA. Phosphorylation of VEGFR2, PDGFR-α, PDGFR-β and c-KIT was not observed in any carcinoma or normal nasal sample, but phosphorylation of EGFR1 was noted in 10/16 carcinoma and 3/5 normal samples. The absence of phosphorylated RTK targets of toceranib suggests any clinical effect of toceranib occurs through inhibition of alternative unidentified RTK pathways in canine nasal carcinomas. The observed protein and message expression and phosphorylation of EGFR1 in the nasal carcinoma samples merits further inquiry into EGFR1 as a therapeutic target for this cancer.

Surfactant Protein A and Napsin A in the Immunohistochemical Characterization of Canine Pulmonary Carcinomas: Comparison With Thyroid Transcription Factor-1

Thyroid transcription factor-1 (TTF-1) is a specific and sensitive marker for canine pulmonary tumors but is also expressed in thyroid carcinomas, which commonly metastasize to lung. Napsin A and surfactant protein A (SP-A) are used in the histologic diagnosis of non-small-cell lung cancer in humans but have not been thoroughly evaluated in neoplasms of dogs. The objective of this study was to compare the efficacy of immunohistochemistry for SP-A, napsin A, and TTF-1 in the diagnosis of canine pulmonary carcinomas. TTF-1, napsin A, and SP-A antibodies were applied to 67 formalin-fixed, paraffin-embedded canine pulmonary tumors. Although each marker had good sensitivity, only 3% (2/67) of lung tumors were negative for SP-A compared with 7% (5/67) and 9% (6/67) for napsin A and TTF-1, respectively. Each antigen was detected in a greater percentage of cells of tumors with acinar or papillary patterns compared with those with squamous differentiation. SP-A immunoreactivity was absent in all 113 nonpulmonary tumors tested. Of 108 normal tissues, SP-A was detected only in lung and in 1 of 6 adrenal, 1 of 3 endometrial, and 1 of 4 hepatic sections. Based on these findings, SP-A and napsin A are useful markers of canine lung epithelial neoplasia. Of these, SP-A is the most sensitive and specific (a possible pitfall is the need to distinguish entrapped normal pulmonary epithelial cells or alveolar macrophages from neoplastic cells) and can be used in combination with TTF-1 or napsin A to improve detection and differentiation of pulmonary carcinomas from metastatic tumors in the canine lung.

Effects of epidermal growth factor receptor kinase inhibition on radiation response in canine osteosarcoma cells

BACKGROUND

Radiation therapy is a palliative treatment modality for canine osteosarcoma, with transient improvement in analgesia observed in many cases. However there is room for improvement in outcome for these patients. It is possible that the addition of sensitizing agents may increase tumor response to radiation therapy and prolong quality of life. Epidermal growth factor receptor (EGFR) expression has been documented in canine osteosarcoma and higher EGFR levels have been correlated to a worse prognosis. However, effects of EGFR inhibition on radiation responsiveness in canine osteosarcoma have not been previously characterized. This study examined the effects of the small molecule EGFR inhibitor erlotinib on canine osteosarcoma radiation responses, target and downstream protein expression in vitro. Additionally, to assess the potential impact of treatment on tumor angiogenesis, vascular endothelial growth factor (VEGF) levels in conditioned media were measured.

RESULTS

Erlotinib as a single agent reduced clonogenic survival in two canine osteosarcoma cell lines and enhanced the impact of radiation in one out of three cell lines investigated. In cell viability assays, erlotinib enhanced radiation effects and demonstrated single agent effects. Erlotinib did not alter total levels of EGFR, nor inhibit downstream protein kinase B (PKB/Akt) activation. On the contrary, erlotinib treatment increased phosphorylated Akt in these osteosarcoma cell lines. VEGF levels in conditioned media increased after erlotinib treatment as a single agent and in combination with radiation in two out of three cell lines investigated. However, VEGF levels decreased with erlotinib treatment in the third cell line.

CONCLUSIONS

Erlotinib treatment promoted modest enhancement of radiation effects in canine osteosarcoma cells, and possessed activity as a single agent in some cell lines, indicating a potential role for EGFR inhibition in the treatment of a subset of osteosarcoma patients. The relative radioresistance of osteosarcoma cells does not appear to be related to EGFR signalling exclusively. Angiogenic responses to radiation and kinase inhibitors are similarly likely to be multifactorial and require further investigation.

Generation of a canine anti-EGFR (ErbB-1) antibody for passive immunotherapy in dog cancer patients

Passive immunotherapy with monoclonal antibodies represents a cornerstone of human anticancer therapies, but has not been established in veterinary medicine yet. As the tumor-associated antigen EGFR (ErbB-1) is highly conserved between humans and dogs, and considering the effectiveness of the anti-EGFR antibody cetuximab in human clinical oncology, we present here a "caninized" version of this antibody, can225IgG, for comparative oncology studies. Variable region genes of 225, the murine precursor of cetuximab, were fused with canine constant heavy gamma and kappa chain genes, respectively, and transfected into Chinese hamster ovary (CHO) DUKX-B11 cells. Of note, 480 clones were screened and the best clones were selected according to productivity and highest specificity in EGFR-coated ELISA. Upon purification with Protein G, the recombinant cetuximab-like canine IgG was tested for integrity, correct assembly, and functionality. Specific binding to the surface of EGFR-overexpressing cells was assessed by flow cytometry and immunofluorescence; moreover, binding to canine mammary tissue was demonstrated by immunohistochemistry. In cell viability and proliferation assays, incubation with can225IgG led to significant tumor cell growth inhibition. Moreover, this antibody mediated significant tumor cell killing via phagocytosis in vitro. We thus present here, for the first time, the generation of a canine IgG antibody and its hypothetical structure. On the basis of its cetuximab-like binding site, on the one hand, and the expression of a 91% homologous EGFR molecule in canine cancer, on the other hand, this antibody may be a promising research compound to establish passive immunotherapy in dog patients with cancer.

EGFR, HER-2 and KRAS in canine gastric epithelial tumors: a potential human model?

Epidermal growth factor receptor (EGFR or HER-1) and its analog c-erbB-2 (HER-2) are protein tyrosine kinases correlated with prognosis and response to therapy in a variety of human cancers. KRAS mediates the transduction of signals between EGFR and the nucleus, and its mutation has been identified as a predictor of resistance to anti-EGFR drugs. In human oncology, the importance of the EGFR/HER-2/KRAS signalling pathway in gastric cancer is well established, and HER-2 testing is required before initiating therapy. Conversely, this pathway has never been investigated in canine gastric tumours. A total of 19 canine gastric epithelial neoplasms (5 adenomas and 14 carcinomas) were retrospectively evaluated for EGFR/HER-2 immunohistochemical expression and KRAS mutational status. Five (35.7%) carcinomas were classified as intestinal-type and 9 (64.3%) as diffuse-type. EGFR was overexpressed (≥1+) in 8 (42.1%) cases and HER-2 (3+) in 11 (57.9%) cases, regardless of tumour location or biological behaviour. The percentage of EGFR-positive tumours was significantly higher in the intestinal-type (80%) than in the diffuse-type (11.1%, p = 0.023). KRAS gene was wild type in 18 cases, whereas one mucinous carcinoma harboured a point mutation at codon 12 (G12R). EGFR and HER-2 may be promising prognostic and therapeutic targets in canine gastric epithelial neoplasms. The potential presence of KRAS mutation should be taken into account as a possible mechanism of drug resistance. Further studies are necessary to evaluate the role of dog as a model for human gastric cancer.

Canine pulmonary adenocarcinoma tyrosine kinase receptor expression and phosphorylation

BACKGROUND

This study evaluated tyrosine kinase receptor (TKR) expression and activation in canine pulmonary adenocarcinoma (cpAC) biospecimens. As histological similarities exist between human and cpAC, we hypothesized that cpACs will have increased TKR mRNA and protein expression as well as TKR phosphorylation. The molecular profile of cpAC has not been well characterized making the selection of therapeutic targets that would potentially have relevant biological activity impossible. Therefore, the objectives of this study were to define TKR expression and their phosphorylation state in cpAC as well as to evaluate the tumors for the presence of potential epidermal growth factor receptor (EGFR) tyrosine kinase activating mutations in exons 18-21. Immunohistochemistry (IHC) for TKR expression was performed using a tissue microarray (TMA) constructed from twelve canine tumors and companion normal lung samples. Staining intensities of the IHC were quantified by a veterinary pathologist as well as by two different digitalized algorithm image analyses software programs. An antibody array was used to evaluate TKR phosphorylation of the tumor relative to the TKR phosphorylation of normal tissues with the resulting spot intensities quantified using array analysis software. Each EGFR exon PCR product from all of the tumors and non-affected lung tissues were sequenced using sequencing chemistry and the sequencing reactions were run on automated sequencer. Sequence alignments were made to the National Center for Biotechnology Information canine EGFR reference sequence.

RESULTS

The pro-angiogenic growth factor receptor, PDGFRα, had increased cpAC tumor mRNA, protein expression and phosphorylation when compared to the normal lung tissue biospecimens. Similar to human pulmonary adenocarcinoma, significant increases in cpAC tumor mRNA expression and receptor phosphorylation of the anaplastic lymphoma kinase (ALK) tyrosine receptor were present when compared to the corresponding normal lung tissue. The EGFR mRNA, protein expression and phosphorylation were not increased compared to the normal lung and no activating mutations were identified in exons 18-21.

CONCLUSIONS

Canine pulmonary adenocarcinoma TKRs are detected at both the mRNA and protein levels and are activated. Further investigation into the contribution of TKR activation in cpAC tumorigenesis is warranted.