Abstract C29: Characterization and identification of specific EGFR mutations in circulating tumor cells (CTCs) isolated from non-small cell lung cancer patients using an antibody independent method, ApoStream™: An update report

Background: A variety of methods for capture of rare CTCs of epithelial origin are available; most employ antibodies to epithelial cell adhesion molecule (EpCAM) and cytokeratin (CK). Using a classic phenotypic definition, a CTC is nucleated, CK(+), CD45(-) cell. However, some CTCs may elude capture as they originate from primary tumor cells which have undergone epithelial-mesenchymal transition (EMT). We report here the use of ApoStream™, a novel dielectrophoresis field-flow-assisted, antibody-free method to isolate CTCs from blood.

Methods: Blood was collected from consented NSCLC patients and processed using ApoStream™. For CTC enumeration comparison, the CellSearch® FDA-approved kit was used. Isolated cells were evaluated with a multiplexed immunofluorescent assay and laser scanning cytometry was applied to identify multiple combinations of positive and/or negative staining for CK/CD45/DAPI and EpCAM. To determine specific EGFR mutations from captured CTCs, samples were analyzed using Improved and Complete Enrichment with CO-amplification at Lower Denaturation temperature (ICE COLD-PCR).

Results: Blood samples from 37 NSCLC patients and 8 healthy volunteers were processed and the results of the cell populations isolated using ApoStream™ are summarized in table. EGFR mutations [exon 19 deletion and exon 21 L858R] were determined and found to be concordant when compared to tumor tissue analysis by Sanger sequencing.

Conclusions: The ApoStream™ platform enriched EpCAM(+) and EpCAM(-) CTCs from the blood of NSCLC patients demonstrating utility in recovering cancer cells with multiple phenotypes. From recovered CTCs, detection of EGFR mutations was possible indicating the clinical relevance and potential utility of CTCs as an alternative to tissue biopsy. Additional sensitivity and complete mutation analysis will be presented. (a portion of this data was presented at 2013 ASCO Annual Meeting, Chicago, IL, USA)

Combating resistance to anti-IGFR antibody by targeting the integrin β3-Src pathway

BACKGROUND

Several phase II/III trials of anti-insulin-like growth factor 1 receptor (IGF-1R) monoclonal antibodies (mAbs) have shown limited efficacy. The mechanisms of resistance to IGF-1R mAb-based therapies and clinically applicable strategies for overcoming drug resistance are still undefined.

METHODS

IGF-1R mAb cixutumumab efficacy, alone or in combination with Src inhibitors, was evaluated in 10 human head and neck squamous cell carcinoma (HNSCC) and six non-small cell lung cancer (NSCLC) cell lines in vitro in two- or three-dimensional culture systems and in vivo in cell line- or patient-derived xenograft tumors in athymic nude mice (n = 6-9 per group). Cixutumumab-induced changes in cell signaling and IGF-1 binding to integrin β3 were determined by Western or ligand blotting, immunoprecipitation, immunofluorescence, and cell adhesion analyses and enzyme-linked immunosorbent assay. Data were analyzed by the two-sided Student t test or one-way analysis of variance.

RESULTS

Integrin β3-Src signaling cascade was activated by IGF-1 in HNSCC and NSCLC cells, when IGF-1 binding to IGF-1R was hampered by cixutumumab, resulting in Akt activation and cixutumumab resistance. Targeting integrin β3 or Src enhanced antitumor activity of cixutumumab in multiple cixutumumab-resistant cell lines and patient-derived tumors in vitro and in vivo. Mean tumor volume of mice cotreated with cixutumumab and integrin β3 siRNA was 133.7 mm(3) (95% confidence interval [CI] = 57.6 to 209.8 mm(3)) compared with those treated with cixutumumab (1472.5 mm(3); 95% CI = 1150.7 to 1794.3 mm(3); P < .001) or integrin β3 siRNA (903.2 mm(3); 95% CI = 636.1 to 1170.3 mm(3); P < .001) alone.

CONCLUSIONS

Increased Src activation through integrin ανβ3 confers considerable resistance against anti-IGF-1R mAb-based therapies in HNSCC and NSCLC cells. Dual targeting of the IGF-1R pathway and collateral integrin β3-Src signaling module may override this resistance.

Tumor grafts derived from patients with head and neck squamous carcinoma authentically maintain the molecular and histologic characteristics of human cancers

BACKGROUND

The patient-derived xenograft (PDX) model is likely to reflect human tumor biology more accurately than cultured cell lines because human tumors are implanted directly into animals; maintained in an in vivo, three-dimensional environment; and never cultured on plastic. PDX models of head and neck squamous cell carcinoma (HNSCC) have been developed previously but were not well characterized at the molecular level. HNSCC is a deadly and disfiguring disease for which better systemic therapy is desperately needed. The development of new therapies and the understanding of HNSCC biology both depend upon clinically relevant animal models. We developed and characterized the patient-derived xenograft (PDX) model because it is likely to recapitulate human tumor biology.

METHODS

We transplanted 30 primary tumors directly into mice. The histology and stromal components were analyzed by immunohistochemistry. Gene expression analysis was conducted on patient tumors and on PDXs and cell lines derived from one PDX and from independent, human tumors.

RESULTS

Five of 30 (17%) transplanted tumors could be serially passaged. Engraftment was more frequent among HNSCC with poor differentiation and nodal disease. The tumors maintained the histologic characteristics of the parent tumor, although human stromal components were lost upon engraftment. The degree of difference in gene expression between the PDX and its parent tumor varied widely but was stable up to the tenth generation in one PDX. For genes whose expression differed between parent tumors and cell lines in culture, the PDX expression pattern was very similar to that of the parent tumor. There were also significant expression differences between the human tumors that subsequently grew in mice and those that did not, suggesting that this model enriches for cancers with distinct biological features. The PDX model was used successfully to test targeted drugs in vivo.

CONCLUSION

The PDX model for HNSCC is feasible, recapitulates the histology of the original tumor, and generates stable gene expression patterns. Gene expression patterns and histology suggested that the PDX more closely recapitulated the parental tumor than did cells in culture. Thus, the PDX is a robust model in which to evaluate tumor biology and novel therapeutics.

Uncommon epidermal growth factor receptor mutations in non-small cell lung cancer and their mechanisms of EGFR tyrosine kinase inhibitors sensitivity and resistance

Therapy targeted against the epidermal growth factor receptor (EGFR) has demonstrated dramatic tumor responses and favorable clinical outcomes in a select group of non-small cell lung cancer (NSCLC) patients whose tumors harbor EGFR activating mutations. The best characterized of the mutations conferring sensitivity to EGFR tyrosine kinase inhibitors (TKIs) are deletions in exon 19 and a point mutation in exon 21 (L858R). Likewise, the most common mutation that confers resistance is the T790M point mutation. However several other mutations have been reported and several have been characterized as regards their role in sensitivity or resistance to EGFR TKIs. Resistance to the EGFR TKIs erlotinib and gefitinib, and the newer irreversible EGFR TKIs is a problem of fundamental importance. Recognition of the presence and significance of specific EGFR mutations is important for appropriate therapeutic implementation of EGFR TKIs and research and development of mutation-specific inhibitors. We summarize the literature and present an overview of the subject of less common EGFR mutations and their clinical significance, with an emphasis on EGFR TKI sensitivity or resistance.

Characterization and identification of specific EGFR mutations in circulating tumor cells (CTCs) isolated from non-small cell lung cancer patients using antibody independent method, ApoStream

11044

Background: A variety of methods for isolation of CTCs of epithelial origin are available; most employ antibodies to epithelial cell adhesion molecule (EpCAM). Using classic phenotypic definition, a CTC is nucleated, cytokeratin CK(+), CD45(-) cell. However, some CTCs may elude capture as they originate from primary tumor cells which have undergone epithelial-mesenchymal transition (EMT). We report here the use of ApoStream, a novel dielectrophoresis field-flow-assisted, antibody-free method to isolate CTCs from blood. Methods: Blood was collected from consented NSCLC patients and processed using ApoStrea. For CTC enumeration comparison, CellSearch FDA-approved kit was used. Isolated cells were evaluated with multiplexed immunofluorescent assay and laser scanning cytometry analysis were applied to identify multiple combinations of positive and/or negative staining for CK/CD45/DAPI and EpCam. To determine specific EGFR mutations from captured CTCs, samples were analyzed using Improved and Complete Enrichment with CO-amplification at Lower Denaturation temperature (ICE COLD-PCR). Results: Blood samples from 32 NSCLC patients and 3 healthy volunteers were processed. ApoStream isolated 0 to 65 CK(+)/CD45(-) CTCs(n=32) and CellSearch isolated 0 to 13 EpCAM(+)/CK(+)/CD45(-) CTCs(n=7). Additionally, ApoStream™ recovered 37-3536 CK(-)/CD45(-) and 4-10702 CK(+)/CD45(+) cells. EpCAM expression was detected in 7-100% of CK(+)/CD45(-) and 0-5% of CK(-)/CD45(-) cells, and 18-100% of CK(+)/CD45(+) cells. EGFR mutations [exon 19 deletion and exon 21 L858R] were determined and found to be concordant when compared to tumor tissue analysis by Sanger sequencing. Conclusions: The ApoStream platform enriched EpCAM(+) and EpCAM(-) CTCs from the blood of NSCLC patients demonstrating utility in recovering cancer cells with multiple phenotypes. From recovered CTCs, detection of EGFR mutations was possible indicating the clinical relevance and potential utility of CTCs as an alternative to tissue biopsy. Complete mutation analysis will be presented.

A phase I/II study combining dasatinib (D) and erlotinib (E) in non-small cell lung cancer

8102

Background: In preclinical models, combining EGFR and Src inhibition has been shown to have at least additive and possibly synergistic effects. In this phase I/II (phI/II) trial, we combined EGFR inhibitor E with D, a multi-targeted tyrosine kinase inhibitor with activity against Src. Primary endpoint of PhI was to determine maximum tolerated dose (MTD) of the combination of E and D; primary endpoint of PhII was progression free survival (PFS) at 12 weeks. Methods: In preclinical models, combining EGFR and Src inhibition has been shown to have at least additive and possibly synergistic effects. In this phase I/II (phI/II) trial, we combined EGFR inhibitor E with D, a multi-targeted tyrosine kinase inhibitor with activity against Src. Primary endpoint of PhI was to determine maximum tolerated dose (MTD) of the combination of E and D; primary endpoint of PhII was progression free survival (PFS) at 12 weeks. Results: 53 pts were enrolled between 2/09 and 4/12. 6 were not eligible. Of the 47 eligible pts (12 in PhI, 35 in PhII): median (range) age was 62 yrs (44-88), 26 pts (45%) were female. 6 pts in PhI and all 35 pts in PhII had NSCLC: adeno 25 pts, squamous 11, NSCLC NOS 5. Other tumor types enrolled in PhI: head and neck cancer (2), adenoid cystic carcinoma (1), mesothelioma (2), small cell lung cancer (1). 47% of pts were chemo-naïve. 8 pts had activating EGFR mutations (6 exon 19 deletions, 2 L858R mutations). The PhI starting dose E150/D100 was not well tolerated as 2 of 3 pts experienced grade 3 hypophosphatemia as a dose limiting toxicity. MTD was found to be E150/D70. 11% achieved PR and 44% SD. All observed responders had EGFR mutations. 9 pts (19%) stopped treatment early and were unevaluable. Median time on treatment was 43 days (range 1-262). Median time on treatment for the 8 pts with activating EGFR mutations was 144 days. Conclusions: Combination of E and D is safe and feasible in NSCLC, with MTD E 150 mg PO daily and D 70 mg PO daily. Rate of PR and SD were 11%,and 44%, respectively. Biomarker and pharmacokinetic studies will be reported. Clinical trial information: NCT00826449.

Abstract 5578: SOCS2 (suppressor of cytokine signaling protein 2) is a prognostic indicator of progression-free survival in head and neck squamous cell carcinoma (HNSCC) patients

HNSCC is a common, deadly, and disfiguring disease. While combinations of radiotherapy, surgery, and chemotherapy are highly effective in HNSCC, there is significant morbidity associated with the disease and recurrence is common. There is great interest in identifying molecular events and pathways which drive HNSCC progression in order that targeted therapies may be developed. The loss of the tumor suppressor function such as p53 and NOTCH1, as well as activation of the STAT3 and STAT5 pathways, has been implicated in HNSCC progression. We have identified interactions between STAT3, STAT5, and the novel tumor suppressor SOCS2 to be important in HNSCC. To extend these findings to humans, we performed experiments to identify prognostic markers in HNSCC and to investigate the expression of STAT3, STAT5, and SOCS2 in HNSCC tissue.

Immunohistochemistry was performed on tissue microarrays from resected tumor specimens of 123 stage I-IVB oral cavity SCC patients (treated with surgery +/- adjuvant radiation therapy) with annotated clinical outcome information from a median follow up of 76 months collected at the UT/MD Anderson Cancer Center. The array was screened with antibodies against STAT5, STAT3, and SOCS2, and scored in a blinded fashion by a pathologist. SOCS2 expression (present vs. absent) correlated significantly with recurrence-free survival in both the univariate (hazard ratio 0.24, p=0.0003; Cox proportional hazards model) and multivariate (hazard ratio 0.24, p=0.0004) analyses. Notably all patients who lacked SOCS2 tumor expression recurred within 45 months. There was a trend towards a correlation of SOCS2 expression with overall survival (HR 0.50, p=0.11) and disease-specific survival (HR 0.52, p=0.28). SOCS2 expression did not significantly correlate with tumor stage and extracapsular extension emphasizing that its absence is an independent marker of poor prognosis. Our prior published work demonstrates that STAT5 drives SOCS2 expression. The expression of SOCS2 in these patient samples positively correlated with total and phosphoSTAT5 (r=0.29 and 0.21 respectively; p&lt;0.05) as well as total and phospho-STAT3 (r=0.27 and 0.26, respectively; p&lt;0.05). Likewise, we measured total and phosphoSTAT3, total and phosphoSTAT5, and SOCS2 in a panel of HNSCC cell lines. SOCS2 protein levels and phosphorylation of STAT3 and STAT5 varied among cell lines, however cells with elevated phosphoSTAT3 and STAT5 also showed elevated SOCS2 protein. This is the first study which identifies SOCS2 as an independent marker of prognosis in HNSCC. In support of its role as a tumor suppressor, the lack of SOSC2 expression was associated with universal recurrence.

This work was supported The University of Texas SPORE in Head and Neck Cancer (P50 CA097007), The Cancer Center Support Grant, and the ASCO Cancer Foundation Young Investigator Award (WW).

Citation Format: Courtney Nicholas, Maria I. Nunez, Nusrat Harun, J. Jack Lee, Jeffrey Myers, Ignacio I. Wistuba, Banibrata Sen, Adel K. El-Naggar, Stephen Y. Lai, Faye M. Johnson, William N. William. SOCS2 (suppressor of cytokine signaling protein 2) is a prognostic indicator of progression-free survival in head and neck squamous cell carcinoma (HNSCC) patients. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5578. doi:10.1158/1538-7445.AM2013-5578

Abstract 4095: Paradoxical activation of the RAF-MEK-ERK pathway in response to nilotinib induces synthetic lethality with MEK inhibition in head and neck cancer cells

Cancers of the head and neck are difficult to treat because both the therapy and the tumor impact essential functions such as speech and swallowing and they can significantly alter facial appearance. The RAS/RAF/MEK/ERK cascade is one of the major signaling pathways that leads to head and neck squamous cell carcinoma (HNSCC) cell survival. There are three RAS genes (HRAS, KRAS, and NRAS) and together, they are mutated in about 30% of human cancers. RAS can also be activated by upstream signaling. Paradoxically RAF inhibition induces RAF-dimerization and causes subsequent activation of MEK/ERK pathway in presence of activated RAS in melanoma. Similarly the ABL inhibitor nilotinib acts as weak inhibitor of RAF kinase and also induces RAF-dimerization and subsequent activation of MEK/ERK in the presence of activated RAS in leukemia and pancreatic cancer cells. Nilotinib synergizes with MEK inhibitition to kill nilotinib-resistant leukemia cells (Abl T351I). We hypothesized that nilotinib and the MEK inhibitor MEK162 would be synergistic in HNSCC due to the frequent activation of RAS via upstream growth factor receptors. RAS mutations are relatively uncommon in HNSCC. We screened 60 validated HNSCC cell lines through sequenome analysis and we found three HNSCC cell lines with activating HRAS mutations (G12D and Q61L) [∼5%]. We found that nilotinib induces significant RAF dimerization and subsequent activation of MEK-ERK pathway irrespective of RAS mutational status. We next investigated how paradoxical MEK/ERK pathway activation affected the growth of HNSCC cells. In this context we treated a panel of HNSCC cell lines harboring WT and mutated HRAS with nilotinib and MEK162. Nilotinib alone had nearly no effect on cell viability and MEK162 had a moderate effect on some HNSCC lines. The combination of nilotinib and MEK162 synergized to inhibit the growth of HNSCC cells independent of RAS mutational status. The drug combination led to an accumulation of cells in G1 and a significant reduction in cell proliferation as measured with BrDU incorporation and colony formation. HNSCC cells with mutant HRAS undergo apoptosis in presence of both the drugs. In contrast none of these drugs induce senescence in HNSCC cell lines. Here we show that in HNSCC, nilotinib as single agent drives the paradoxical activation of RAF-MEK-ERK pathway in RAS mutation-independent manner and we uncovered a synthetic lethal pathway that can be used treat HNSCC. Animal studies are planned.

This work was supported by University of Texas SPORE in Head and Neck Cancer P50 CA097007.

Citation Format: Banibrata Sen, Tuhina Mazumdar, Shaohua Peng, Katherine S. Hale, Bonnie S. Glisson, Faye M. Johnson. Paradoxical activation of the RAF-MEK-ERK pathway in response to nilotinib induces synthetic lethality with MEK inhibition in head and neck cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4095. doi:10.1158/1538-7445.AM2013-4095

Abstract 5645: Angiogenic activity leads failure of antitumor activity of cixutumumab, an anti-Insulin like growth factor receptor monoclonal antibody

The type 1 insulin-like growth factor receptor (IGF-1R) signaling is dysregulated in many cancers, thus being a target of cancer therapy. Several preclinical trials have reported the efficacy of IGF-1R targeted therapies, mostly using tyrosine kinase inhibitors or monoclonal antibodies (mAbs); however many of clinical trials have shown limited therapeutic efficacy. In this study, we investigated the resistance mechanism to IGF-1R mAb-based therapies using cixutumumab, a fully humanized mAb against IGF-1R. We tested the efficacy of cixutumumab using OSC19 and 686LN head and neck squamous cell carcinoma (HNSCC) and MDA-MB-231 breast cancer orthotopic and H1299 non-small cell lung cancer (NSCLC) xenograft tumor models. We observed that cixutumumab treatment induced either no change or increased tumor growth and decreased the survival duration of the animals bearing those tumors. Treatment with cixutumumab upregulated migration and invasion of HNSCC and NSCLC cells without any effects on cell proliferation. We further examined the effects of cixutumumab on tumor angiogenesis and found that conditioned media from cancer cells treated with cixutumumab increased tube formation and migration of human umbilical endothelial cells (HUVECs). The angiogenic activity of cixutumumab was also confirmed by matrigel plug assay with HNSCC cell lines. Collectively, these data suggest that cixutumumab-induced angiogenesis-stimulating activities and migration and invasion potential of cancer cells are major factors of resistance to IGF-1R mAbs. These data further suggest that inhibitors of angiogenesis are useful strategy to overcome the resistance against the IGF-1R mAb-based therapy.

Citation Format: Ji-Sun Lee, Ju-Hee Kang, Hye-Jin Boo, Jeffrey N. Myers, Faye M. Johnson, Bonnie S. Glisson, Seoung-Hyun Oh, Ho-Young Lee. Angiogenic activity leads failure of antitumor activity of cixutumumab, an anti-Insulin like growth factor receptor monoclonal antibody. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5645. doi:10.1158/1538-7445.AM2013-5645

Kinase-impaired BRAF mutations in lung cancer confer sensitivity to dasatinib

During a clinical trial of the tyrosine kinase inhibitor dasatinib for advanced non-small cell lung cancer (NSCLC), one patient responded dramatically and remains cancer-free 4 years later. A comprehensive analysis of his tumor revealed a previously undescribed, kinase-inactivating BRAF mutation ((Y472C)BRAF); no inactivating BRAF mutations were found in the nonresponding tumors taken from other patients. Cells transfected with (Y472C)BRAF exhibited CRAF, MEK (mitogen-activated or extracellular signal-regulated protein kinase kinase), and ERK (extracellular signal-regulated kinase) activation-characteristics identical to signaling changes that occur with previously known kinase-inactivating BRAF mutants. Dasatinib selectively induced senescence in NSCLC cells with inactivating BRAF mutations. Transfection of other NSCLC cells with these BRAF mutations also increased these cells' dasatinib sensitivity, whereas transfection with an activating BRAF mutation led to their increased dasatinib resistance. The sensitivity induced by (Y472C)BRAF was reversed by the introduction of a BRAF mutation that impairs RAF dimerization. Dasatinib inhibited CRAF modestly, but concurrently induced RAF dimerization, resulting in ERK activation in NSCLC cells with kinase-inactivating BRAF mutations. The sensitivity of NSCLC with kinase-impaired BRAF to dasatinib suggested synthetic lethality of BRAF and an unknown dasatinib target. Inhibiting BRAF in NSCLC cells expressing wild-type BRAF likewise enhanced these cells' dasatinib sensitivity. Thus, the patient's BRAF mutation was likely responsible for his tumor's marked response to dasatinib, suggesting that tumors bearing kinase-impaired BRAF mutations may be exquisitely sensitive to dasatinib. Moreover, the potential synthetic lethality of combination therapy including dasatinib and BRAF inhibitors may lead to additional therapeutic options against cancers with wild-type BRAF.

Global evaluation of Eph receptors and ephrins in lung adenocarcinomas identifies EphA4 as an inhibitor of cell migration and invasion

The Eph family of receptors is the largest family of receptor tyrosine kinases, but it remains poorly studied in lung cancer. We aimed to systematically explore the human Eph receptors and their ligands, the ephrins, in lung adenocarcinoma. The prognostic impact of Eph receptor and ephrin gene expression was analyzed using 2 independent cohorts of lung adenocarcinoma. Gene expression profiles in lung adenocarcinoma compared with normal adjacent lung were studied in 3 independent cohorts and in cell lines. Gene expression profiles were validated with quantitative polymerase chain reaction (qPCR) and Western blotting in cell lines. Functional studies to assess the role of Eph receptor A4 (EphA4) were carried out in vitro. The biological effects of EphA4 in lung cancer cell lines were assayed following overexpression and knockdown. Of the 11 Eph receptors and 8 ephrins analyzed, only EphA4 and ephrin A1 gene expression were consistently associated with an improved outcome in patients with lung adenocarcinoma. Expression levels of EphA4 by microarray correlated well with expression levels measured by qPCR and Western blotting. EphA4 overexpression reduced cell migration and invasion but did not affect cell cycle, apoptosis, or drug sensitivity. Surprisingly, EphA4 was expressed at higher levels in cancer compared with non-cancer tissues and cell lines. EphA4 gene expression is associated with an improved outcome in patients with resected lung adenocarcinoma, possibly by affecting cancer cell migration and invasion.

Abstract 2361: Establishing a patient-derived heterotransplant mouse model of head and neck squamous carcinoma (HNSCC)

There are approximately 47,000 new cases of head and neck cancer diagnosed in the United States each year. The survival rate has not improved significantly in the past 30 years. The development of new therapies for HNSCC and the understanding of its biology both depend upon clinically relevant animal models. There are several existing animal models for HNSCC that include chemically-induced cancer models, syngeneic models using animal cancer cells, transgenic mice, and xenograft models using cultured human HNSCC cell lines injected into immunocompromised mice, either subcutaneously or orthotopically. An increasingly promising xenograft model, the heterotransplant model, is developed by surgically implanting tumor tissue directly from a patient into an immunocompromised mouse. The resulting tumor is serially passaged in vivo and never cultured on plastic. We have transplanted 20 HNSCC primary tumors from untreated patients directly into mice that included 17 tongue tumors, one maxillary gingival tumor, and two from the floor of the mouth. Although several tumors grew initially in mice, only 2 of 20 (10%) established tumors that could be serially passaged and used for therapeutic and mechanistic studies. One cell line has been established from a tongue heterotransplant (HOSC1). The two established heterotransplants maintained the histological appearance of the original tumors. To test the biological and molecular signaling response of HNSCC to targeted therapy, we utilized one heterotransplant that was passaged into 40 mice. Both the Src inhibitor dasatinib and the JAK inhibitor INCB16562 modestly inhibited tumor growth; the combination was significantly more effective than the single agents. Likewise, the tumors treated with the combination had significantly more apoptosis and less proliferation than control tumors. Consistent with our published in vitro results, Src inhibition did not result in STAT3 inhibition, but JAK inhibition abrogated STAT3 activation. Src was inhibited in vivo by dasatinib. Our results demonstrate that the heterotransplant model of HNSCC has promise as an in vivo model to test the efficacy of anti-cancer drugs. The low “take rate” is problematic but will be addressed in the future by intra-operative biopsies and larger tumor specimens.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2361. doi:1538-7445.AM2012-2361

STAT5A-mediated SOCS2 expression regulates Jak2 and STAT3 activity following c-Src inhibition in head and neck squamous carcinoma

PURPOSE

The inhibition of c-Src results in a striking reduction in cancer cell invasion, but the effect on cell survival is modest. Defining mechanisms that limit apoptosis following c-Src inhibition could result in an ideal therapeutic approach that both inhibits invasion and leads to apoptosis. In this regard, we discovered a novel feedback loop that results in STAT3 reactivation following sustained c-Src inhibition. Here we define the mechanism underlying this feedback loop and examine the effect of inhibiting it in vivo.

EXPERIMENTAL DESIGN

We measured levels and activity of pathway components using PCR, Western blotting, and kinase assays following their manipulation using both molecular and pharmacologic approaches. We used a heterotransplant animal model in which human oral squamous cancer is maintained exclusively in vivo.

RESULTS

Following c-Src inhibition, STAT5 is durably inhibited. The inhibition of STAT5A, but not STAT5B, subsequently reduces the expression of suppressors of cytokine signaling 2 (SOCS2). SOCS2 inhibits Janus kinase 2 (Jak2) activity and Jak2-STAT3 binding. SOCS2 expression is necessary for STAT3 inhibition by c-Src inhibitors. Overexpression of SOCS2 is adequate to prevent STAT3 reactivation and to enhance the cytotoxic effects of c-Src inhibition. Likewise, the combination of Jak and c-Src inhibitors led to significantly more apoptosis than either agent alone in vivo.

CONCLUSIONS

To our knowledge, ours is the first study that fully defines the mechanism underlying this feedback loop, in which sustained c-Src inhibition leads to diminished SOCS2 expression via sustained inhibition of STAT5A, allowing activation of Jak2 and STAT3, Jak2-STAT3 binding, and survival signals.

Abstract 1046: Differential interactions between c-Src and c-Met mediate resistance to c-Src inhibitors

Cancers of the head and neck are difficult to treat because both the therapy and the tumor impact essential functions such as speech and swallowing and they can also significantly alter facial appearance. One promising molecular target for which new agents have been developed is the Src family kinases (SFKs). SFK inhibition in cancer cells leads to an universal abrogation of invasion but a variable and weak effects on apoptosis and proliferation. The pathways downstream of c-Src promoting survival are not well-characterized. Because cancer therapy that both decreases invasion and induces significant apoptosis would be ideal for head and neck cancers, we sought to characterize the mechanisms of resistance to SFK inhibition in Head and Neck squamous cell carcinoma (HNSCC). SFKs were inhibited in a panel of oral cancer cell lines and the effects on subsequent survival and signaling were measured. The interactions between c-Src and c-Met were evaluated using immunoprecitation and their intrinsic kinase activity by in vitro kinase assay. Cytotoxicity was measured using an MTT assay and the Chou-Talalay combination index calculated. The in vivo effects of c-Met and SFK inhibitors were assessed using an orthotopic model of oral cancer. SFK inhibition resulted in c-Met inhibition in cell lines that were sensitive to SFK inhibitors, but not in resistant cell lines. Isolated c-Met act as a c-Src substrate in both sensitive and resistant cells, whereas distinct difference exists in c-Src and c-Met interaction in intact sensitive and resistant cells. The epidermal growth factor receptor contributed to c-Met activation in resistant cells whereas in sensitive cells c-Met acts as a direct downstream target for c-Src. We demonstrated the biological consequences of this mechanism in vitro with synergistic cytotoxicity and enhanced apoptosis when SFK and c-Met inhibitors were combined. Likewise, the combination resulted in decreased tumor size in vivo. In conclusion, we demonstrate that sustained c-Met activation can mediate resistance to SFK inhibition. The differences between c-Src and c-Met signaling in sensitive and resistant cells are not due to intrinsic structural changes in c-Src or c-Met, but rather to distinct interactions within the intact cells. The synergistic cytotoxic effects of SFK and c-Met inhibition may be important for the treatment of head and neck cancers and should be tested in future clinical trials.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1046. doi:10.1158/1538-7445.AM2011-1046

Distinct interactions between c-Src and c-Met in mediating resistance to c-Src inhibition in head and neck cancer

PURPOSE

c-Src inhibition in cancer cells leads to an abrogation of invasion but a variable effect on apoptosis. The pathways downstream of c-Src promoting survival are not well characterized. Because cancer therapy that both decreases invasion and induces significant apoptosis would be ideal, we sought to characterize the mechanisms of resistance to c-Src inhibition.

EXPERIMENTAL DESIGN

c-Src was inhibited in a panel of oral cancer cell lines and subsequent survival and signaling measured. The interactions between c-Src and c-Met were evaluated using immunoprecitation and an in vitro kinase assay. Cytotoxicity was measured and the Chou-Talalay combination index calculated. An orthotopic model of oral cancer was used to assess the effects of c-Met and c-Src inhibitors.

RESULTS

Inhibition of c-Src resulted in c-Met inhibition in sensitive cells lines, but not in resistant cell lines. Isolated c-Met was a c-Src substrate in both sensitive and resistant cells, but there was no interaction of c-Src and c-Met in intact resistant cells. To examine the biological consequences of this mechanism, we demonstrated synergistic cytotoxicity, enhanced apoptosis, and decreased tumor size with the combination of c-Src and c-Met inhibitors.

CONCLUSIONS

Sustained c-Met activation can mediate resistance to c-Src inhibition. These data suggest that the differences between c-Met and c-Src signaling in sensitive and resistant cells are due to distinct factors promoting or inhibiting interactions, respectively, rather than to intrinsic structural changes in c-Src or c-Met. The synergistic cytotoxic effects of c-Src and c-Met inhibition may be important for the treatment of head and neck cancers.

Src inhibitors in lung cancer: current status and future directions

Src tyrosine kinases regulate multiple genetic and signaling pathways involved in the proliferation, survival, angiogenesis, invasion, and migration of various types of cancer cells They are frequently expressed and activated in many cancer types, including lung cancer. Several Src inhibitors, including dasatinib, saracatinib, bosutinib, and KX2-391, are currently being investigated in clinical trials. Preliminary results of the use of single-agent Src inhibitors in unselected patients with lung cancer show that these inhibitors have a favorable safety profile and anticancer activity. Their combination with cytotoxic chemotherapy, other targeted therapy, and radiation therapy is currently being explored. In this review, we summarize the rationale for and the current status of Src inhibitor development and discuss future directions based on emerging preclinical data.

Phase II study of dasatinib in patients with advanced non-small-cell lung cancer

PURPOSE

Src family kinases (SFKs) promote cancer progression and are commonly expressed in non-small-cell lung cancer (NSCLC), but the clinical effects of SFK inhibition in NSCLC are unknown. We conducted a phase II trial of the SFK inhibitor dasatinib for advanced NSCLC. We tested the hypotheses that the activation of epidermal growth factor receptor (EGFR) or SFK or modulation of serum cytokines may predict a response to dasatinib.

PATIENTS AND METHODS

Patients received dasatinib as first-line therapy. Response was measured by tumor size on computed tomography scans and by metabolic activity on positron emission tomography scans. Tissue samples taken before patients received dasatinib were tested for EGFR and Kras mutation and phosphorylated SFK expression.

RESULTS

Thirty-four patients were enrolled. The overall disease control rate (partial responses plus stable disease) for dasatinib was 43%. One patient had a partial response to therapy. Eleven patients (32%) had a metabolic response to dasatinib. SFK activation and EGFR and Kras mutations in tumor tissue did not predict response to dasatinib. Significant toxicities included fatigue and dyspnea. The presence of a pleural effusion before dasatanib therapy predicted the development of a clinically significant effusion during therapy.

CONCLUSION

Dasatinib as a single agent had modest clinical activity that was lower than that generally observed in patients with NSCLC who receive chemotherapy. Pleural effusion was an expected and problematic toxicity that was successfully treated with steroids, diuretics, and dose interruptions. Marked activity in one patient and prolonged stable disease in four others suggested a potential subpopulation of patients with dasatinib-sensitive NSCLC.

Drosophila melanogaster: Inheritance of a Deficiency of Alkaline Phosphatase in Larvae

A deficiency of the normally prominent alkaline phosphatase zone (by starch-gel electrophoresis) has been discovered in a newly investigated laboratory strain of Drosophila melonogaster. Mating experiments indicate that genetic control is by an allele of a previously described electrophoretic variation. Heterozygotes resulting from crosses of the deficient type and the fast electrophoretic variant show only the fast phenotype. In deficient x slow heterozygotes, however, there is a new band that does not correspond in electrophoretic mobility with any of the bands of other heterozygous or homozygous types. It is suggested that the allele responsible for the deficiency leads to the manufacture of an inactive subunit that is able to hybridize with the subunits of the slow electrophoretic form.

Epidermal growth factor receptor expression and gene copy number in the risk of oral cancer

Leukoplakia is the most common premalignant lesion of the oral cavity. Epidermal growth factor receptor (EGFR) abnormalities are associated with oral tumorigenesis and progression. We hypothesized that EGFR expression and gene copy number changes are predictors of the risk of an oral premalignant lesion (OPL) progressing to oral squamous cell carcinoma (OSCC). A formalin-fixed, paraffin-embedded OPL biopsy specimen was collected from each of 162 patients in a randomized controlled clinical trial. We assessed EGFR expression by immunohistochemistry with two

METHODS

a semiquantitative analysis (145 evaluable specimens) and an automated quantitative analysis (127 evaluable specimens). EGFR gene copy number was assessed by fluorescence in situ hybridization (FISH) in a subset of 49 OPLs with high EGFR expression defined by the semiquantitative analysis. We analyzed EGFR abnormalities for associations with OSCC development. High EGFR expression occurred in 103 (71%) of the 145 OPLs and was associated with a nonsignificantly higher risk of OSCC (P = 0.10). Twenty (41%) of 49 OPLs assessed by FISH had an increased EGFR gene copy number (FISH-positive). Patients with FISH-positive lesions had a significantly higher incidence of OSCC than did patients with FISH-negative (a normal copy number) lesions (P = 0.0007). Of note, 10 of 11 OSCCs that developed at the site of the examined OPL were in the FISH-positive group, leaving only one FISH-negative OPL that did so (P < 0.0001). Our data indicate that an increased EGFR gene copy number is common in and associated with OSCC development in patients with OPLs expressing high EGFR, particularly OSCC developing at the site of a high-expression OPL; they also suggest that EGFR inhibitors may prevent oral cancer in patients with OPLs having an increased EGFR gene copy number.

Weekly alternating therapy with irinotecan plus cisplatin and etoposide plus cisplatin in the treatment of patients with extensive small cell lung carcinoma

BACKGROUND

Irinotecan has significant activity in small-cell lung cancer (SCLC). The authors' previous phase 1 study of alternating weekly therapy with irinotecan/cisplatin (IP), etoposide/cisplatin (EP), and granulocyte-colony-stimulating factor (G-CSF) support was well tolerated and active in patients with SCLC. A phase 2 trial was conducted to estimate the efficacy of this regimen in previously untreated patients with extensive SCLC.

METHODS

A total of 33 patients were treated between June 2002 and July 2007. Patients received 12 weeks of therapy with cisplatin (20 mg/m(2)) on Day 1 and irinotecan (100 mg/m(2)) on Day 1 and G-CSF on Days 2 to 5 (Weeks 1, 3, 5, 7, 9, and 11) followed by cisplatin (20 mg/m(2)) on Day 1 and etoposide (60 mg/m(2)) on Days 1 to 3 with G-CSF on Days 4 to 7 (Weeks 2, 4, 6, 8, 10, and 12). The primary endpoint was 1-year survival rate.

RESULTS

Grade 4 neutropenia (toxicities were determined using the National Cancer Institute Common Toxicity Criteria [version 2.0]) was noted in 5 (1.5%) of 343 courses with neutropenic fever in only 5 (1%) of 343 courses. One patient died of neutropenic sepsis. Nonhematologic toxicities grade >or=2 were observed in 15 (4%) of 343 courses and were limited to fatigue, hyponatremia, and diarrhea. The overall objective response rate was 89% in 28 assessable patients (no complete responses and 25 partial responses). The median progression-free and overall survivals were 6.0 months and 10.9 months, respectively. The 1-year survival rate was 33%.

CONCLUSIONS

Weekly therapy with IP alternating with EP and G-CSF support was well tolerated in patients with extensive SCLC, but did not demonstrate improved progression-free or overall survival when compared with historical controls at the study institution.

Defining the role of the JAK-STAT pathway in head and neck and thoracic malignancies: implications for future therapeutic approaches

Although the role of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway has been most extensively studied in hematopoietic cells and hematologic malignancies, it is also activated in epithelial tumors, including those originating in the lungs and head and neck. The canonical pathway involves the activation of JAK following ligand binding to cytokine receptors. The activated JAKs then phosphorylate STAT proteins, leading to their dimerization and translocation into the nucleus. In the nucleus, STATs act as transcription factors with pleiotropic downstream effects. STATs can be activated independently of JAKs, most notably by c-Src kinases. In cancer cells, STAT3 and STAT5 activation leads to the increased expression of downstream target genes, leading to increased cell proliferation, cell survival, angiogenesis, and immune system evasion. STAT3 and STAT5 are expressed and activated in head and neck squamous cell carcinoma (HNSCC) where they contribute to cell survival and proliferation. In HNSCC, STATs can be activated by a number of signal transduction pathways, including the epidermal growth factor receptor (EGFR), alpha7 nicotinic receptor, interleukin (IL) receptor, and erythropoietin receptor pathways. Activated STATs are also expressed in lung cancer, but the biological effects of JAK/STAT inhibition in this cancer are variable. In lung cancer, STAT3 can be activated by multiple pathways, including EGFR. Several approaches have been used to inhibit STAT3 in the hopes of developing an antitumor agent. Although several STAT3-specific agents are promising, none are in clinical development, mostly because of drug delivery and stability issues. In contrast, several JAK inhibitors are in clinical development. These orally available, ATP-competitive, small-molecule kinase inhibitors are being tested in myeloproliferative disorders. Future studies will determine whether JAK inhibitors are useful in the treatment of HNSCC or lung cancer.

Phase 1 pharmacokinetic and drug-interaction study of dasatinib in patients with advanced solid tumors

BACKGROUND

The recently developed the Src and Abelson (Abl) kinase inhibitor dasatinib has antitumor effects in epithelial and mesenchymal tumors. Preclinical data have indicated that dasatinib is metabolized primarily through cytochrome P450 3A4 (CYP3A4) and may cause QT prolongation. In light of its improved tolerability, the authors were interested in the safety of a once-daily dasatinib regimen.

METHODS

The authors conducted a phase 1 trial of dasatinib in 29 patients with advanced solid tumors. Segment 1 of the trial was short term and sequential and was designed to determine whether the coadministration of the potent CYP3A4 inhibitor ketoconazole had an effect on the pharmacokinetics of dasatinib. Segment 2 was designed to evaluate the safety of dasatinib as dosing was increased. QT intervals were monitored closely in both segments. Efficacy was assessed in Segment 2 using both positron emission tomography and computed tomography.

RESULTS

Hematologic toxicities were markedly less than those observed in patients with leukemia, whereas nonhematologic toxicities were similar. The authors determined that the maximum recommended dose was 180 mg once daily based on the incidence of pleural effusion. Coadministration of ketoconazole led to a marked increase in dasatinib exposure, which was correlated with an increase in corrected QT (QTc) values of approximately 6 msec. No adverse cardiac events were observed.

CONCLUSIONS

The dose-limiting toxic effect for dasatinib was pleural effusion. The pharmacokinetic and cardiac studies indicated that coadministration of dasatinib with potent CYP3A4 inhibitors or agents that prolong the QTc interval should be avoided if possible. Close monitoring for toxicity and dose reduction should be considered if the coadministration of such agents cannot be avoided.

Abstract 4005: JAK/STAT activation following Src inhibition is mediated by the loss of SOCS2 expression

Systemic therapy that results in both decreased invasion and significant cytotoxicity would be ideal to treat head and neck squamous cell carcinoma (HNSCC). One promising therapeutic target is Src due to its well-defined roles in both invasion and survival. STAT3 is a key mediator of the oncogenic effects of Src. However we previously found that sustained Src inhibition resulted in only transient inhibition of STAT3. Likewise, Src inhibition resulted in a universal reduction in invasion, but a more variable effect on apoptosis. Restoring STAT3 inhibition enhanced apoptosis. Previously we showed that STAT3 reactivation was mediated by JAK2 kinase activation and altered JAK2-STAT3 binding. Reactivation of JAK2/STAT3 suggests a feedback loop, possibly via the loss of a negative regulator. Of the three known feedback loops that regulate JAK/STAT function, we considered the most likely candidate to be the suppressors of cytokine signaling (SOCS) proteins, which can compete for STAT binding and inhibit JAK kinase activity. To determine if SOCS proteins are involved in JAK/STAT3 reactivation, we measured RNA levels of all 8 SOCS family members in 5 HNSCC cell lines using quantitative PCR. The expression of most of the SOCS decrease after initial Src inhibition, but recover, consistent with their regulation by STAT3. However, the expression of SOCS2 decreased in all 5 lines. Likewise, we found that the addition of a molar stoichiometric amount of recombinant SOCS2 inhibits Jak2 kinase activity in vitro. To confirm that SOCS2 regulates STAT3 activity, we knocked-down SOCS2 by siRNA which resulted in the activation of STAT3. Similarly, transient overexpression of SOCS2 resulted in significant downregulation of activated STAT3. Others have reported that STAT5 can regulate SOCS2 expression. Consistent with this, we found that Src inhibition led to durable STAT5 inhibition. Moreover, the depletion of both isoforms of STAT5 (a and b) with siRNA resulted in a dramatic downregulation of the SOCS2 expression. To determine the biological significance of SOCS2 expression, we discovered that specific SOCS2 depletion reduced HNSCC cytotoxicity following Src inhibition. Our results demonstrate that sustained Src inhibition leads to the loss of SOCS2 expression via STAT5 inhibition. The loss of SOCS2 allows the recovery of JAK2 kinase activity, JAK2/STAT3 binding, STAT3 activation, and cell survival despite durable Src inhibition. To our knowledge, this feedback pathway has never been described previously. Given that pharmacologic Src and JAK inhibitors are currently being evaluated in clinical trials, these results have significant implications for cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4005.