Abstract P6-11-09: FAK Inhibitor VS-4718 Attenuates Breast Cancer Stem Cell Function In Vitro and In Vivo

Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that mediates signal transduction by integrins as well as growth factor receptors. FAK has been implicated in multiple steps of carcinogenesis including tumor initiation, growth and metastasis. Amplification and overexpression of FAK have been observed in aggressive human cancers including breast cancer. We have now observed that VS-4718, a selective FAK kinase inhibitor, exhibits preferential inhibitory effects on breast cancer stem cells.

VS-4718 is a potent and selective FAK kinase inhibitor that blocks fibronectin-stimulated FAK autophosphorylation at Tyr397 at low nanomolar concentrations. To determine if FAK plays a role in the biology of breast cancer stem cells, VS-4718 was evaluated in a multitude of cancer stem cell assays both in vitro and in vivo. In parallel, treatment of SUM159 triple negative breast cancer cells in vitro with FAK shRNA inhibits tumorsphere formation. These data taken together indicate a role of FAK in breast cancer stem cell renewal. Similarly, pre-treatment of SUM159 cells with VS-4718 in matrigel attenuated secondary tumorsphere formation. Furthermore, VS-4718 reduced the side population (SP) and the percentage of ALDEFLUOR+ cancer stem cells in SUM159 breast cancer cells in vitro. In direct contrast, standard-of-care agent paclitaxel increased the percentage of ALDEFLUOR+ cancer stem cells in all three assays.

The in vivo effect of VS-4718 on cancer stem cells was evaluated in SUM159 and MDA-MB-231 human triple negative breast cancer xenograft models. Following systemic administration, VS-4718 induced significant reduction of cancer stem cells in tumors as assessed by a decrease in ALDEFLUOR+ cells and tumorsphere-forming efficiency relative to vehicle-treated tumors.

In summary, our results indicate the importance of FAK in the self-renewal of breast cancer stem cells in vitro and in vivo, and support the clinical development of the selective FAK inhibitor VS-4718 to target cancer stem cells for the treatment of triple negative breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-11-09.

Farnesoid X receptor regulates vascular reactivity through nitric oxide mechanism

Farnesoid X receptor (FXR), a ligand-activated transcription factor and a member of nuclear receptor family, is not only highly expressed in the adrenal cortex, intestine, kidney and liver, but also has recently been found in the vasculature. However, the evidence on the roles of FXR in the vasculature is limited and whether FXR regulates vascular reactivity is poorly understood. In present study, we investigated the expression of FXR protein in rat vasculature by immunohistochemical method and tested the effects of FXR activation by chenodeoxycholic acid (CDCA) on thoracic aortic contraction and dilation. We also detected the level of nitrite/nitrate (NOx) and superoxide in the thoracic aortic segments. We found that FXR was expressed in rat carotid arteries, thoracic aorta, abdominal aorta and femoral arteries. FXR activation by CDCA significantly (P<0.01) inhibited the contractile responses of rat thoracic aorta rings to KCl and phenylephrine. The cumulative concentrations of CDCA caused a concentration-dependent relaxation, which could be partly impaired by L-NAME, an inhibitor of nitric oxide (NO) synthase. The NOx content in thoracic aorta significantly (P<0.01) increased when treated with CDCA. Meanwhile, the vascular redox status was not altered by high concentration of CDCA. The present study suggested that FXR regulated vascular reactivity through NO mechanism, which merits further attention.

SU-F-BRCD-09: Total Variation (TV) Based Fast Convergent Iterative CBCT Reconstruction with GPU Acceleration

PURPOSE

To improve image quality and reduce imaging dose in CBCT for radiation therapy applications and to realize near real-time image reconstruction based on use of a fast convergence iterative algorithm and acceleration by multi-GPUs.

METHODS

An iterative image reconstruction that sought to minimize a weighted least squares cost function that employed total variation (TV) regularization was employed to mitigate projection data incompleteness and noise. To achieve rapid 3D image reconstruction (< 1 min), a highly optimized multiple-GPU implementation of the algorithm was developed. The convergence rate and reconstruction accuracy were evaluated using a modified 3D Shepp-Logan digital phantom and a Catphan-600 physical phantom. The reconstructed images were compared with the clinical FDK reconstruction results.

RESULTS

Digital phantom studies showed that only 15 iterations and 60 iterations are needed to achieve algorithm convergence for 360-view and 60-view cases, respectively. The RMSE was reduced to 10-4 and 10-2, respectively, by using 15 iterations for each case. Our algorithm required 5.4s to complete one iteration for the 60-view case using one Tesla C2075 GPU. The few-view study indicated that our iterative algorithm has great potential to reduce the imaging dose and preserve good image quality. For the physical Catphan studies, the images obtained from the iterative algorithm possessed better spatial resolution and higher SNRs than those obtained from by use of a clinical FDK reconstruction algorithm.

CONCLUSIONS

We have developed a fast convergence iterative algorithm for CBCT image reconstruction. The developed algorithm yielded images with better spatial resolution and higher SNR than those produced by a commercial FDK tool. In addition, from the few-view study, the iterative algorithm has shown great potential for significantly reducing imaging dose. We expect that the developed reconstruction approach will facilitate applications including IGART and patient daily CBCT-based treatment localization.

SU-E-J-139: Feasibility of Using EPID for Real-Time Target Localization during Treatment

PURPOSE

This study aims to investigate the feasibility of using the images of the treatment fields acquired by an electronic portal imaging device (EPID) for real-time target localization.

METHODS

Forty one patients treated with IMRT and RapidArc were recruited in this study including 37 prostate patients and 4 lung patients. These patients were grouped as: prostate IMRT with lymph node (n=14), prostate IMRT without lymph node (n=17), prostate RapidArc (n=6), and lung IMRT (n=4). For each patient, two to four fiducial markers were implanted inside the tumor. The DRR, which projects the patient anatomy and the fiducial marker at the EPID location, was reconstructed for each field. The MLC aperture of each control point was overlay on its corresponding DRR to evaluate the fractional time when the fiducial marker was seen on the EPID image. The probability of seeing at least one, two, three, and four fiducial markers during the treatment was recorded.

RESULTS

For the prostate IMRT patients without lymph nodes included in the target volume, the average probability of seeing at least one, two, three, and four fiducial markers during the treatment was 50% (35%-59%), 39% (23%-51%), 24% (7%-38%), and 12% (4%-29%), respectively. For the prostate IMRT patients with lymph nodes, the probability was 41% (24%-51%), 29% (12%-42%), 15% (3%-24%), and 7% (4%-15%), respectively. For prostate RapidArc treatments using two arcs, the average probability of seeing at least one fiducial marker was 81% (58%-90%) for the full arc and 74% (53%-94%) for the partial arc. For the lung IMRT treatment, the average probability of seeing at least one fiducial marker was 34% (20%-52%).

CONCLUSIONS

The continuous image acquisition from the EPID during the treatment provides sufficient target movement information for real-time target localization and intrafractional target motion correction for advanced radiotherapy treatments.

MicroRNA expression profiling identifies miR-328 regulates cancer stem cell-like SP cells in colorectal cancer

Background:

Side population (SP) cells and their relationship to stem cell-like properties have been insufficiently studied in colorectal cancer (CRC). MicroRNAs (miRNAs) have attracted much attention but their roles in the maintenance of SP phenotype remain unclear.

Methods:

The SPs from CRC cell lines and primary cell cultures were analysed for stem cell-like properties. MiRNA microarray analysis identified miR-328 as a potential stemness miRNA of SP phenotype. The level of miR-328 expression in clinical samples and its correlation with SP fraction were determined. Gain-of-function and loss-of-function studies were performed to examine its roles in cancer stem-like SP cells. Furthermore, bioinformatics prediction and experimental validation were used to identify miR-328 target genes.

Results:

The SP cells sorted from CRC possess cancer stem cell (CSC)-like properties, including self-renewal, differentiation, resistance to chemotherapy, invasive and strong tumour formation ability. MiR-328 expression was significantly reduced in SP cells compared with Non-SP cells (P<0.05). Moreover, miR-328 expression was downregulated in CRC (n=33, P<0.05) and low miR-328 expression tend to correlate with high SP fraction (n=15, r=0.6559, P<0.05, Pearson's correlation). Functional studies indicated that miR-328 expression affects the number of SP cells. In addition, miR-328 overexpression reversed drug resistance and inhibited cell invasion of SP cells. Furthermore, luciferase reporter assay demonstrated that miR-328 directly targets ABCG2 and MMP16 and affects the levels of mRNA and protein expression in SP cells.

Conclusion:

These findings indicate that CRC contain cancer stem-like SP cells. MiR-328 has an important role in maintaining cancer stem-like SP phenotype that may be a potential target for effective CRC therapy.

Gastric haemolymphangioma: a literature review and report of one case

Gastric haemolymphangioma is a very rare benign tumour. Pathologically, it is composed of lymphatic vessels and blood vessels. Only a few cases of haemolymphangioma have been reported in the literature so far, all of which developed at sites other than the stomach. The authors believe that a haemolymphangioma occurring in the stomach has not been previously reported. The patient was a healthy 68-year-old male who had felt light epigastric discomfort for 3 months. A CT scan and a gastrofiberscope examination revealed a well-demarcated mass on the posterior wall of the stomach near the lesser curvature. The mass was successfully removed by surgery. During the 18-month follow-up period, the patient was asymptomatic with no recurrence. In this case report, we discuss the imaging findings as well as the pathological features of this unusual case, with a review of the related literature.

Enhanced S-adenosyl-l-methionine production in Saccharomyces cerevisiae by spaceflight culture, overexpressing methionine adenosyltransferase and optimizing cultivation

AIMS

S-adenosyl-l-methionine (SAM) is an important biochemical molecule with great potential in the pharmacological and chemotherapeutic fields. In this study, our aims were to enhance SAM production in Saccharomyces cerevisiae.

METHODS AND RESULTS

Through spaceflight culture, a SAM-accumulating strain, S. cerevisiae H5M147, was isolated and found to produce 86·89% more SAM than its ground control strain H5. Amplified fragment length polymorphism (AFLP) analysis demonstrated that there were genetic variations between strain H5M147 and its ground control. Through recombinant DNA technology, the heterologous gene encoding methionine adenosyltransferase was integrated into the genome of strain H5M147. The recombinant strain H5MR83 was selected because its SAM production was increased by 42·98% when compared to strain H5M147. Furthermore, cultivation conditions were optimized using the one-factor-at-a-time and Taguchi methods. Under optimal conditions, strain H5MR83 yielded 7·76 g l(-1) of SAM in shake flask, an increase of 536·07% when compared to the strain H5. Furthermore, 9·64 g l(-1) of SAM was produced in fermenter cultivation.

CONCLUSIONS

A new SAM-accumulating strain, S. cerevisiae H5MR83, was obtained through spaceflight culture and genetic modification. Under optimal conditions, SAM production was increased to a relative high level in our study.

SIGNIFICANCE AND IMPACT OF THE STUDY

Through comprehensive application of multiple methods including spaceflight culture, genetic modification and optimizing cultivation, the yield of SAM could be increased by 6·4 times compared to that in the control strain H5. The obtained S. cerevisiae H5MR83 produced 7·76 g l(-1) of SAM in the flask cultures, a significant improvement on previously reported results. The SAM production period with S. cerevisiae H5MR83 was 84 h, which is shorter than previously reported results. Saccharomyces cerevisiae H5MR83 has considerable potential for use in industrial applications.