Topoisomerase‐1 and ‐2A gene copy numbers are elevated in mismatch repair‐proficient colorectal cancers

Introduction

Topoisomerase 1 (TOP1) and 2A (TOP2A) are potential predictive biomarkers for irinotecan and anthracycline treatment, respectively, in colorectal cancer (CRC), and we have recently reported a high frequency of gene gain of the TOP1 and TOP2A genes in CRC. Furthermore, Mismatch Repair (MMR) subtypes of CRC have been associated with benefit from adjuvant chemotherapy of primary CRC. Given the involvement of the topoisomerase enzymes in DNA replication and repair, we raised the hypothesis that an association may exist between TOP gene copy numbers and MMR proficiency/deficiency in CRC.

Material and methods

Test cohort: FISH analysis with an in‐house TOP1/CEN20 probe mix and a commercially available TOP2A/CEN17 (Dako, Glostrup, Denmark) probe mix was performed on archival formalin fixed paraffin embedded (FFPE) tissue samples from 18 patients with proficient MMR (pMMR) CRC and 18 patients with deficient MMR (dMMR) CRC. TOP1 and TOP2A gene copy numbers and their ratios per nucleus were correlated with MMR status using the Mann–Whitney test. Validation cohort: FFPE samples from 154 patients with primary stage III CRC (originally included in the RANX05 study) were classified according to MMR status by immunohistochemical analysis using validated antibodies for MLH1, MLH2, MSH6 and PMS2, and information on TOP1, CEN20, TOP2A and CEN17 status was previously published for this cohort.

Results

The observed TOP1 gene copy numbers in the 36 CRC test cohort were significantly greater (p < 0.01) in the pMMR subgroup (mean: 3.84, SD: 2.03) than in the dMMR subgroup (mean: 1.50, SD: 0.12). Similarly, the TOP2A copy numbers were significantly greater (p < 0.01) in the pMMR subgroup (mean: 1.99, SD: 0.52) than in the dMMR subgroup (mean: 1.52, SD: 0.10). These findings were confirmed in the validation cohort, where in the pMMR subgroup 51% had ≥2 extra TOP1 copies per cell, while all tumors classified as dMMR had diploid TOP1 status and mean TOP2A copy numbers were 2.30 (SD: 1.36) and 1.80 (SD: 0.31) (p = 0.01) in the pMMR subgroup vs. dMMR subgroup, respectively.

Discussion and conclusion

Our results show that TOP1 and TOP2A gene copy numbers are increased in the pMMR subgroup. We propose that this preference may reflect a selective pressure to gain and/or maintain the gained extra copies of topoisomerase genes whose products are required to cope with high replication stress present in the pMMR tumors, thereby providing a survival advantage selectively in pMMR tumors. Future studies should test this concept and explore potential differences between pMMR and dMMR tumors in response to Top1 and Top2 inhibitors.     

Improved bone biomechanical properties in xylitol-fed aged rats.

Our previous studies have shown that dietary xylitol protects against weakening of bone biomechanical properties in experimental postmenopausal osteoporosis. To study whether xylitol preserves bone biomechanics also during aging, a long-term experimental study was performed with rats. Twenty-four male Sprague-Dawley rats were divided into 2 groups. The rats in the control group (NON-XYL group) were fed a basal rat and mouse no. 1 maintenance (RM1) diet, while the rats in the experimental group (XYL group) were continuously fed the same diet supplemented with 10% xylitol (wt/wt). The rats were killed after 20 months. Their femurs were prepared for biomechanical analyses and scanning analyses with peripheral quantitative computed tomography (pQCT). In 3-point bending of the femoral diaphysis, maximum load, maximum elastic load, stiffness, energy absorption, elastic energy absorption, ultimate stress, and yield stress were significantly greater in the XYL group than in the NON-XYL group. This indicates a xylitol-induced improvement of both structural and material strength properties of cortical bone. Accordingly, the maximum load of femoral neck was significantly greater in the XYL group. In the pQCT analysis of femoral diaphysis, cortical bone area, cortical thickness (CtTh) periosteal circumference, and cross-sectional moment of inertia were greater in the XYL group. The endosteal circumference was smaller in the XYL group. In the pQCT analysis of the femoral neck cortical area of the midneck was significantly greater in the XYL group. This data indicates that xylitol exerted beneficial effects on the cross-sectional architecture of the bones. In conclusion, continuous moderate dietary xylitol supplementation leads to improved bone biomechanical properties in aged rats concerning both bone structural and material strength properties.     

A prospective study on congenital and acquired cytomegalovirus infections in infants.

A preliminary report is presented on a current prospective virological and clinical study of congenital and acquired infant cytomegalovirus (CMV) infections. During a 1-year period, 7/2200 newborn Swedish infants investigated (0.3%) had a congenital CMV infection as shown by positive virus isolation. Two of them had typical symptoms, hepatosplenomegaly and petechiae in one case and splenomegaly in the other one. All of them had a normal birth weight and normal head circumference. No sequelae have been observed during an observation period of up to 9 months. Five out of 10 control infants followed-up acquired a CMV infection within a few months. 5/7 mothers of the congenitally infected infants and 3/14 mothers of the control infants were primiparas.     

Isolation of differentially expressed aldose reductase in ovaries after estrogen withdrawal from hypophysectomized diethylstilbestrol treated rats: increased expression during apoptosis

More than 99% of the follicles are eliminated by apoptosis before reaching ovulation. Several growth factors and hormones inhibit apoptosis in the ovary, including estrogen. Using differential display of mRNA, aldose reductase was shown to increase in the ovary of diethylstilbestrol treated hypophysectomized rats after estrogen withdrawal, inducing apoptosis. The aldose reductase mRNA expression was confirmed to be 2.2 +/- 0.2-fold higher after estrogen withdrawal using northern blot analysis. In addition, untreated immature rats showed a 1.7 +/- 0.3-fold higher expression of ovarian aldose reductase mRNA compared to ovaries 24 h after pregnant mare's serum gonadotropin treatment, decreasing apoptosis in the ovary. In the prostate, the level of aldose reductase was increased 3.1 +/- 1.1-fold 2 days after castration induced apoptosis. Although the physiological role of aldose reductase in the ovary is not known, these data suggest that aldose reductase may be part of a hormonally regulated apoptotic pathway in the ovary and prostate.     

Treatment of severe haemoptysis by embolisation of the bronchial artery. A case report.

A case report is presented of a 50-year-old man with severe haemoptysis. The exact source of the bleeding was not known and medical treatment had no effect. Selective angiography of the bronchial arteries showed extravasation of the contrast medium into a bronchus. Embolisation of the bleeding bronchial artery caused the haemoptysis to stop immediately.     

Fluid balance monitoring by cuff-occluded rate of rise of peripheral venous pressure in haemodialysis patients

Cuff-occluded rate of rise of peripheral venous pressure has been proposed to reflect volume changes in experimental studies. The aim of this study was to evaluate changes in cuff-occluded rate of rise of peripheral venous pressure associated with fluid removal by haemodialysis in six adult patients with chronic renal failure on intermittent haemodialysis. Measurements were carried out before and after each haemodialysis session. The volume of fluid removed (indexed to body surface area) linearly correlated with changes in cuff-occluded rate of rise of peripheral venous pressure (r = 0.84; r(2) = 0.70; p = 0.037). Cuff-occluded rate of rise of peripheral venous pressure may be feasible for future clinical monitoring of individual fluid balance.     

GSK-3 inhibition by an orally active small molecule increases bone mass in rats

Glycogen synthase kinase 3β (GSK-3β) actions are central in the canonical Wnt pathway, important in many biological processes and a potential drug target for treating several diseases. It is appreciated that a balanced Wnt canonical signaling is crucial for the maintenance of normal bone mass. In this study we investigated the effects of a potent orally active GSK-3 inhibitor, AZD2858, on bone mass in rats. Treatment (1 μM) of human osteoblast cells with AZD2858 in vitro increased β-catenin levels after a short period of time. In rats, oral AZD2858 treatment caused a dose-dependent increase in trabecular bone mass compared to control after a two-week treatment with a maximum effect at a dose of 20 mg/kg once daily (total BMC: 172% of control; p<0.001). A small but significant effect was also seen at cortical sites (total BMC: 111% of control; p<0.001). Biomechanical testing demonstrated an increase in both vertebral compression strength at a dose of 20 mg/kg once daily (Load at failure: 370% of control, p<0.001) and diaphyseal strength of femora subjected to a three point bending test (Load at failure: 115% of control; p<0.01). Furthermore, histomorphometry showed a dramatic increase in bone formation indices, and serum markers of both bone formation (Osteocalcin, 146% of control; p<0.001) and resorption (CTX, 189% of control; p<0.001) were elevated. Our conclusion is that a GSK-3 inhibitor drug may prove effective as an anabolic strategy in the treatment of diseases characterized by low bone mass, since AZD2858 has extensive bone building effects at predominantly trabecular sites.     

Right ventricular strain predicts adverse outcomes in patients undergoing coronary artery bypass grafting

The International Journal of Cardiovascular Imaging - Patients undergoing coronary artery bypass grafting (CABG) face an elevated risk of heart failure (HF) and cardiovascular (CV) death. Detailed...     

Colonic mucosal tears in collagenous colitis

In general, the colonic mucosa is macroscopically normal in collagenous colitis, although minor, non-specific abnormalities may be found. Significant endoscopic abnormalities, “mucosal tears” representing longitudinal mucosal lacerations, have been reported in a few patients with collagenous colitis. We report the cases of three women with collagenous colitis and mucosal tears detected at the index colonoscopy in order to illustrate the endoscopic characteristics and review the literature. Including the present cases, a total of 12 patients with mucosal tears and collagenous colitis have been reported. In 10 patients, the mucosal lacerations involved the ascending or the transverse colon. Three of the 12 patients had a colonic perforation immediately after the colonoscopy. The colonoscopist should be aware that the risk of perforation is likely to be increased when mucosal tears are present.