Steven Lau

An integrin alpha(v)beta(3)-c-Src oncogenic unit promotes anchorage-independence and tumor progression.

Integrins regulate adhesion-dependent growth, survival and invasion of tumor cells. In particular, expression of integrin αvβ3 is associated with progression of a variety of human tumors. Here we reveal a previously undescribed adhesion-independent role for integrin αvβ3 in pancreatic cancer and other carcinomas. Specifically, αvβ3 expressed in carcinoma cells enhanced anchorage-independent tumor growth in vitro and increased lymph node metastases in vivo. These effects required recruitment of c-Src to the β3 integrin cytoplasmic tail, leading to c-Src activation, Crk-associated substrate (CAS) phosphorylation and tumor cell survival that, unexpectedly, was independent of cell adhesion or focal adhesion kinase (FAK) activation. Pharmacological blockade of c-Src kinase activity or decreased expression of endogenous αvβ3 integrin or c-Src not only inhibited anchorage-independent growth but also suppressed metastasis in vivo, yet these manipulations did not affect tumor cell migration or invasion. These data define an unexpected role for an integrin as a mediator of anchorage independence, suggesting that an αvβ3–c-Src signaling module may account for the aggressive behavior of integrin αvβ3–expressing tumors in humans.

Specific Cross-talk between Epidermal Growth Factor Receptor and Integrin αvβ5 Promotes Carcinoma Cell Invasion and Metastasis

Tyrosine kinase receptors and integrins play essential roles in tumor cell invasion and metastasis. Previously, we showed that epidermal growth factor (EGF) stimulation of pancreatic carcinoma cells led to invasion and metastasis that was blocked by antagonists of integrin alpha(v)beta(5). Here, we show that EGF stimulates metastasis of carcinoma cells via a Src-dependent phosphorylation of p130 CAS leading to activation of Rap1, a small GTPase involved in integrin activation. Specifically, EGF receptor (EGFR)-induced Src activity leads to phosphorylation of a region within the CAS substrate domain, which is essential for Rap1 and alpha(v)beta(5) activation. This pathway induces alpha(v)beta(5)-mediated invasion and metastasis in vivo yet does not influence primary tumor growth or activation of other integrins on these cells. These findings show cross-talk between a tyrosine kinase receptor and an integrin involved in carcinoma cell invasion and metastasis and may explain in part how inhibitors of EGFR affect malignant disease.

Correlation Between Radiation Dose to 18F-FDG-PET Defined Active Bone Marrow Subregions and Acute Hematologic Toxicity in Cervical Cancer Patients Treated With Chemoradiotherapy

PURPOSE To test the hypothesis that radiation dose to (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET)-defined active bone marrow (BM(ACT)) subregions is correlated with hematologic toxicity in cervical cancer patients treated with chemoradiotherapy. METHODS AND MATERIALS The conditions of 26 women with cervical cancer who underwent (18)F-FDG-PET before treatment with concurrent cisplatin and intensity-modulated radiation therapy were analyzed. BM(ACT) was defined as the subregion of total bone marrow (BM(TOT)) with a standardized uptake value (SUV) equal to or above the mean for that individual. Inactive bone marrow (BM(INACT)) was defined as BM(TOT) - BM(ACT). Generalized linear modeling was used to test the correlation between BM(ACT) and BM(INACT) dose-volume metrics and hematologic nadirs, particularly white blood cell count (WBC) and absolute neutrophil count (ANC). RESULTS Increased BM(ACT) mean dose was significantly associated with decreased log(WBC) nadir (β = -0.04; 95% CI, -0.07 to -0.01; p = 0.009), decreased log(ANC) nadir (β = -0.05; 95% CI, -0.08 to -0.02; p = 0.006), decreased hemoglobin nadir (β = -0.16; 95% CI, -0.27 to -0.05; p = 0.010), and decreased platelet nadir (β = -6.16; 95% CI, -9.37 to -2.96; p < 0.001). By contrast, there was no association between BM(INACT) mean dose and log(WBC) nadir (β = -0.01; 95% CI, -0.06 to 0.05; p = 0.84), log(ANC) nadir (β = -0.03; 95% CI, -0.10 to 0.04; p = 0.40), hemoglobin nadir (β = -0.09; 95% CI, -0.31 to 0.14; p = 0.452), or platelet nadir (β = -3.47; 95% CI, -10.44 to 3.50; p = 0.339). CONCLUSIONS Irradiation of BM subregions with higher (18)F-FDG-PET activity was associated with hematologic toxicity, supporting the hypothesis that reducing dose to BM(ACT) subregions could mitigate hematologic toxicity. Future investigation should seek to confirm these findings and to identify optimal SUV thresholds to define BM(ACT).

RBBP9: A tumor-associated serine hydrolase activity required for pancreatic neoplasia

Pancreatic cancer is one of the most lethal malignancies. To discover functionally relevant modulators of pancreatic neoplasia, we performed activity-based proteomic profiling on primary human ductal adenocarcinomas. Here, we identify retinoblastoma-binding protein 9 (RBBP9) as a tumor-associated serine hydrolase that displays elevated activity in pancreatic carcinomas. Whereas RBBP9 is expressed in normal and malignant tissues at similar levels, its elevated activity in tumor cells promotes anchorage-independent growth in vitro as well as pancreatic carcinogenesis in vivo. At the molecular level, RBBP9 activity overcomes TGF-β-mediated antiproliferative signaling by reducing Smad2/3 phosphorylation, a previously unknown role for a serine hydrolase in cancer biology. Conversely, loss of endogenous RBBP9 or expression of mutationally inactive RBBP9 leads to elevated Smad2/3 phosphorylation, implicating this serine hydrolase as an essential suppressor of TGF-β signaling. Finally, RBBP9-mediated suppression of TGF-β signaling is required for E-cadherin expression as loss of the serine hydrolase activity leads to a reduction in E-cadherin levels and a concomitant decrease in the integrity of tumor cell–cell junctions. These data not only define a previously uncharacterized serine hydrolase activity associated with epithelial neoplasia, but also demonstrate the potential benefit of functional proteomics in the identification of new therapeutic targets.

Oncogenic Ras/Src cooperativity in pancreatic neoplasia

Pancreas cancer is one of the most lethal malignancies and is characterized by activating mutations of Kras, present in 95% of patients. More than 60% of pancreatic cancers also display increased c-Src activity, which is associated with poor prognosis. Although loss of tumor suppressor function (for example, p16, p53, Smad4) combined with oncogenic Kras signaling has been shown to accelerate pancreatic duct carcinogenesis, it is unclear whether elevated Src activity contributes to Kras-dependent tumorigenesis or is simply a biomarker of disease progression. Here, we demonstrate that in the context of oncogenic Kras, activation of c-Src through deletion of C-terminal Src kinase (CSK) results in the development of invasive pancreatic ductal adenocarcinoma (PDA) by 5–8 weeks. In contrast, deletion of CSK alone fails to induce neoplasia, while oncogenic Kras expression yields PDA at low frequency after a latency of 12 months. Analysis of cell lines derived from Ras/Src-induced PDAs indicates that oncogenic Ras/Src cooperativity may lead to genomic instability, yet Ras/Src-driven tumor cells remain dependent on Src signaling and as such, Src inhibition suppresses growth of Ras/Src-driven tumors. These findings demonstrate that oncogenic Ras/Src cooperate to accelerate PDA onset and support further studies of Src-directed therapies in pancreatic cancer.

EGFR-Mediated Carcinoma Cell Metastasis Mediated by Integrin αvβ5 Depends on Activation of c-Src and Cleavage of MUC1

Receptor tyrosine kinases and integrins play an essential role in tumor cell invasion and metastasis. We previously showed that EGF and other growth factors induce human carcinoma cell invasion and metastasis mediated by integrin αvβ5 that is prevented by Src blockade [1]. MUC1, a transmembrane glycoprotein, is expressed in most epithelial tumors as a heterodimer consisting of an extracellular and a transmembrane subunit. The MUC1 cytoplasmic domain of the transmembrane subunit (MUC1.CD) translocates to the nucleus where it promotes the transcription of a metastatic gene signature associated with epithelial to mesenchymal transition. Here, we demonstrate a requirement for MUC1 in carcinoma cell metastasis dependent on EGFR and Src without affecting primary tumor growth. EGF stimulates Src-dependent MUC1 cleavage and nuclear localization leading to the expression of genes linked to metastasis. Moreover, expression of MUC1.CD results in its nuclear localization and is sufficient for transcription of the metastatic gene signature and tumor cell metastasis. These results demonstrate that EGFR and Src activity contribute to carcinoma cell invasion and metastasis mediated by integrin αvβ5 in part by promoting proteolytic cleavage of MUC1 and highlight the ability of MUC1.CD to promote metastasis in a context-dependent manner. Our findings may have implications for the use and future design of targeted therapies in cancers known to express EGFR, Src, or MUC1.

Stereotactic body radiation therapy in octogenarians with stage I lung cancer.

BACKGROUND The purpose of this study was to describe our clinical experience using stereotactic body radiation therapy (SBRT) to treat medically inoperable stage I non-small-cell lung cancer (NSCLC) in very elderly patients. PATIENTS AND METHODS Twenty-four consecutive octogenarians with stage I NSCLC were treated with SBRT between 2007 and 2011 at a single center. Median prescription dose was 48 Gy (range, 48-56). Follow-up clinical examination and computed tomography (CT) were performed every 2 to 3 months. RESULTS Median age was 85 years (range, 80-89). Twenty-three (96%) patients had peripheral tumors, and median tumor size was 22 mm (range, 11-49). Tissue diagnosis was obtained in 16 (67%) patients. Median follow-up for all patients was 27.6 months (range, 4.3-61.2). The 24-month disease-free survival was 77% (95% confidence interval [CI], 61%-97%). The 24-month overall survival (OS) was 74% (95% CI, 57%-94%). No local failure (LF) was observed during the period of observation. Nodal failure (NF) and distant failure (DF) occurred in 2 and 4 patients, respectively. The cumulative incidence of competing mortality at 24 months was estimated at 13% (95% CI, 3%-30%). No difference in outcomes with or without tissue diagnosis was observed. No grade ≥ 3 early or late treatment-related toxicities were observed. CONCLUSION Octogenarians tolerate SBRT well, which makes it an attractive treatment option.

Single-Isocenter Frameless Volumetric Modulated Arc Radiosurgery for Multiple Intracranial Metastases.

BACKGROUND Stereotactic radiosurgery (SRS) is a well-accepted treatment for patients with intracranial metastases, but outcomes with volumetric modulated arc radiosurgery (VMAR) are poorly described. OBJECTIVE To report our initial clinical experience applying a novel single-isocenter technique to frameless VMAR for simultaneous treatment of multiple intracranial metastases. METHODS We performed a retrospective analysis of 15 patients undergoing frameless VMAR for multiple intracranial metastases using a single, centrally located isocenter in the period 2009 and 2011. Of these, 3 patients were treated for progressive or recurrent intracranial disease. A total of 62 metastases (median, 3 per patient; range, 2-13) were treated to a median dose of 20 Gy (range, 15-30 Gy). Three patients were treated with fractionated SRS. Follow-up including clinical examination and magnetic resonance imaging (MRI) occurred every 3 months. RESULTS The median follow-up for all patients was 7.1 months (range, 1.1-24.3), with 11 patients (73.3%) followed until death. For the remaining 4 patients alive at the time of analysis, the median follow-up was 19.6 months (range, 9.2-24.3). Local control at 6 and 12 months was 91.7% (95% confidence interval [CI], 84.6%-100.0%) and 81.5% (95% CI, 67.9%-100.0%), respectively. Regional failure was observed in 9 patients (60.0%), and 7 patients (46.7%) received salvage therapy. Overall survival at 6 months was 60.0% (95% CI, 40.3%-88.2%). Grade 3 or higher treatment-related toxicity was not observed. The median total treatment time was 7.2 minutes (range, 2.8-13.2 minutes). CONCLUSION Single-isocenter, frameless VMAR for multiple intracranial metastases is a promising technique that may provide similar clinical outcomes compared with conventional radiosurgery.

Local Therapy for Limited Metastatic Non-Small Cell Lung Cancer: What Are the Options and Is There a Benefit?

Distant metastasis is common in non-small cell lung cancer (NSCLC) and typically associated with poor prognosis. Aggressive local therapy including surgery and/or radiation for limited metastatic disease from colorectal cancer and sarcoma is associated with survival benefit and has become part of the standard of care. In this article, we review the literature and ongoing studies concerning surgery, radiation, and radiofrequency ablation for oligometastatic NSCLC.

Reporting of cause-specific treatment effects in cancer clinical trials with competing risks: A systematic review

BACKGROUND Separate analysis of cause-specific treatment effects is important for interpreting results of randomized trials. We sought to determine the extent to which cause-specific effects on primary events are reported in contemporary randomized controlled trials in oncology. METHODS We screened 833 randomized trials published in eight leading medical journals between January 2006 and December 2009. We excluded prevention studies (n=52), secondary reports (n=100), and one retracted study. Analysis was further restricted to 116 trials in non-metastatic/recurrent cancer that used an event-free survival primary endpoint. For each study included in the analysis, we evaluated whether treatment effects on both cancer and non-cancer events comprising the primary endpoint were reported separately and whether statistical analysis was provided. RESULTS Of the 116 randomized trials, 47 (40%; 95% confidence interval (CI), 32-50%) reported effects on both cancer and non-cancer events comprising the primary endpoint, with statistical analysis provided in 13 (11%; 95% CI, 7-19%). Twenty-six trials (22%; 95% CI, 15-31%) reported effects on cancer but not non-cancer events, with statistical analysis provided in 11 (9%; 95% CI, 5-17%). In 43 studies (37%; 95% CI, 28-47%), no effects on cancer-specific components of the primary endpoint were given. Of these, 33 studies (28%; 95% CI, 21-38%) did report effects on some cancer-specific event, while ten (9%; 95% CI, 4-16%) did not report effects of treatment on any cancer event. DISCUSSION Many randomized trials in oncology do not report cause-specific effects on primary events. Increased specificity is needed in the design and reporting of cancer clinical trials.