Src family kinase targeting in head and neck tumor cells using SU6656, PP2 and dasatinib

BACKGROUND

We have recently shown a frequent upregulation of Src-family kinases (SFK) in head and neck squamous cell carcinoma (HNSCC). Here we tested, if SFK targeting is effective especially in HNSCC cells with upregulated SFK signaling.

METHODS

The impact of SFK inhibitors SU6656, PP2 and dasatinib on three HNSCC cell lines with different SFK activity levels was analyzed using proliferation and colony formation assays, Western blot and functional kinomics.

RESULTS

Proliferation was blocked by all inhibitors in a micro-molar range. With respect to cell kill, dasatinib was most effective, while SU6656 showed moderate and PP2 minor effects. Cellular signaling was affected differently, with PP2 having no effect on SFK signaling while dasatinib probably has non-SFK specific effects. Only SU6656 showed clear SFK specific effects on signaling.

CONCLUSION

The results demonstrate potential benefit of SFK inhibition in HNSCC but they also highlight challenges due to non-specificities of the different drugs.

Kinomic comparison of snap frozen and ex vivo-cultured head and neck tumors

OBJECTIVES

The use of primary tumor tissue in experimental and pre-clinical cancer research is becoming increasingly important. Especially the use of tissue slice cultures of tumor specimen, so called ex vivo cultures or tumor explants, promises functional analysis under approximate physiological conditions. This includes screening and testing of targeted therapeutics directed against deregulated protein kinases. However, it is unclear if ex vivo cultures indeed represent the in situ situation especially with respect to very sensitive and transient molecular processes such as kinase dependent signaling. We now asked here, if and to what extent ex vivo culturing affects kinase activity.

MATERIALS AND METHODS

We analyzed the activity of protein tyrosine kinases (PTK) using functional kinome profiling of either snap frozen or ex vivo-cultured tumor tissue samples of head and neck cancer patients.

RESULTS

Although we observed a quantitative decline in overall kinase activity after 24 h or 48 h of ex vivo cultivation, we most importantly noticed that the signaling characteristics were conserved in most samples; approximately two thirds of all ex vivo-cultured samples displayed a signaling pattern which was qualitatively comparable to the parental tumor. We could also demonstrate kinase inhibition by treatment of ex vivo slice cultures with the multi-kinase inhibitor staurosporine, although higher concentrations were needed compared to cell cultures.

CONCLUSION

We here demonstrate that the tyrosine kinase dependent signaling is conserved under exvivo culturing conditions in the majority of samples, which highlights the power of this method in experimental and pre-clinical cancer research.

Serum albumin level predicts survival of patients with gastrointestinal acute graft-versus-host disease after allogeneic stem cell transplantation

In a retrospective single-centre study, we analysed the prognostic impact of factors identifiable at initial diagnosis of acute GVHD (aGVHD). We retrospectively analysed 495 adult patients of whom 308 (62 %) developed acute GVHD (I-IV) and were included in further analysis. Gut aGVHD was diagnosed in 163/308 cases (53 %). Conditioning was myeloablative conditioning (MAC) in 123 (39.9 %) and reduced intensity (RIC) in 185 (60.1 %) patients. Median serum albumin level at diagnosis of aGVHD was 34 g/l, which was used as cut-off for low vs. normal albumin levels. In patients with gut aGVHD, low albumin level at the time of diagnosis of aGVHD was associated with poorer overall survival (OS) which was 52 vs. 67 % at 1 year and 40 vs. 61 % at 3 years, p = 0.015. In patients with only skin aGVHD, 1- and 3-year OS of patients with low vs. normal albumin levels were 72 vs. 72 % and 59 vs. 57 %, respectively, p = 0.69. In multivariate analysis of patients with gut aGVHD, low serum albumin level ≤34 g/l (relative risk (RR) 2.13, p = 0.003), gut aGVHD grades 3-4 (RR 2.70, p = 0.001), RIC (RR 1.84, p = 0.024), matched unrelated donor (RR 1.86, p = 0.18) and mismatched unrelated donor (RR 2.76, p = 0.03) retained negative impact on OS. Subgroup analysis revealed that impact of albumin was restricted to patients with gut aGVHD after RIC. Low serum albumin levels are associated with poorer OS in patients with gut but not skin aGVHD after RIC but not MAC allogeneic stem cell transplantation.

82 EFFECT OF DONOR CELL TRANSFECTION EVENTS ON EMBRYO AND FETAL SURVIVAL IN CLONING

In a large-scale bovine cloning program intended to obtain transgenic animals, it is important to maximize the number of calves produced. The present experiment was designed to test the hypothesis that different transfection events of the same somatic cell line can affect embryo and/or fetal survival. A fetal cell line was established from a 75-day-old Jersey female fetus. It was used as control and was also transfected 3 times with the same protocol. They were named Transfection 1, 2, and 3. Genetically modified cells were produced and isolated after selection with geneticin for 10–15 days following liposome transfection with a DNA construct containing a selectable neomycin resistance gene. Oocytes were aspirated from slaughterhouse ovaries and matured in TCM-199 + 5% FCS at 39°C for 24 h. Matured oocytes were denuded by vortexing for 3 min in TL-HEPES with 1 mg mL−1 bovine testis hyaluronidase. Metaphases were assessed, and oocytes were enucleated by visualization with Hoechst 33342 (5 µg mL−1) under UV light (<6 s). Donor cells from different treatments were used for nuclear transfer at G0/G1 cell cycle stages and were fused to enucleated oocytes by an electrical pulse. After 3 h, activation was induced by incubation in TL-HEPES with 5 µM ionomycin for 4 min and 2 mM 6-DMAP for 3 h. The oocytes were then washed with TL-HEPES and cultured in SOF medium with an atmosphere of 5% CO2 + 5% O2 + 90% N2. Development to blastocysts (Days 7 to 9) was recorded. Two blastocysts were transferred nonsurgically per recipient cow, and pregnancies at 30 days were determined by ultrasonography. All data were analyzed by chi-square test. In vitro development to blastocysts was similar in all treatment groups. One birth was obtained from the control. Four and 7 births were obtained from Transfections 1 and 3, respectively. Although Transfection 2 had good in vitro development, this treatment did not produce any pregnancy. This fact demonstrated that the transfection event provides an additional source of variability in obtaining live transgenic animals. Our results pointed out the necessity to monitor fetal survival by ultrasonography in order to detect as soon as possible any deficiencies in development introduced by transfection. Table 1.Effect of different transfection events of same line on embryo and fetal survival

The environment of cytochrome P-450 in testicular microsomes

The effects of trypsin, phospholipase A, and chymotrypsin on NADPH-cytochrome c reductase and cytochrome P-450 of microsomes from cryptorchid mouse testes and liver were compared. Trypsin released both enzymes almost completely from testis microsomes, while it readily released only NADPH-cytochrome c reductase from liver microsomes. Chymotrypsin alone, even under conditions where 30-40% of the microsomal protein was hydrolyzed, had little effect on localization or activity of either enzyme in either tissue. Phospholipase A destroyed cytochrome P-450 in testicular microsomes but had little effect on this enzyme in hepatic microsomes or on NADPH-cytochrome c reductase in either preparation. When, however, the microsomes were incubated with chymotrypsin in the presence of a detergent, the effects were similar to those of trypsin alone; testicular cytochrome P-450 was destroyed, while hepatic cytochrome P-450 was only slightly solubilized, and NADPH-cytochrome c reductase from both types of microsomes was both solubilized and activated. From these results we conclude that arginyl and/or lysyl bonds may play a significant role in the junction between the hydrophobic region of the membrane and the anchor region of the reductase molecule and that cytochrome P-450 of testicular microsomes is more superficially located in the lipid bilayer than is hepatic microsomal cytochrome P-450.

Effects of trypsin and phospholipases A2 and C on enzyme organization in testis microsomes

Pregnenolone and progesterone concentrated in the microsomal fraction of cryptorchid mouse testis compared with mitochondria and cytosol. While the concentrating mechanisms had high capacity and low association constants the effect did not seem to be due to nonspecific solubility in the lipid components since 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione and testosterone did not show differential concentration. Also digestion with phospholipases A2 and C to the point where most of the phospholipids were specifically split, only lowered the differential binding of pregnenolone and progesterone by less than half. Trypsin had a greater effect, short digestion at 0 degrees C lowering the specific binding to 35-40% and decreasing the steroid dehydrogenases to a similar extent. The members of the mixed function oxidase system in the testis microsomes were particularly sensitive to trypsin, cytochrome P-450 and, as a consequence, 17alpha-hydroxylase and 17, 20-lyase activity being eliminated under tha same conditions while liver microsomal cytochrome P-450 was hardly affected. Bonds split by trypsin seem to play a more important role in the hydroxylase activity of testis microsomes than in the hepatic system.