Does a bicycle accident as the cause of proximal femur fracture indicate that geriatric co-management is superfluous? A retrospective cohort study.

BACKGROUND: Deployment of geriatric care would be more sustainable if we could limit geriatric co-management to older hip fracture patients who benefit most from it. We assumed that riding a bicycle is a proxy of good health and hypothesized that older patients with a hip fracture due to a bicycle accident have a more favorable prognosis than patients whose hip fracture was caused by another type of accident. METHODS: Retrospective cohort study of hip fracture patients ≥ 70 years admitted to hospital. Nursing home residents were excluded. Primary outcome was length of hospital stay (LOS). Secondary outcomes were delirium, infection, blood transfusion, intensive care unit stay and death during hospitalization. The group with a bicycle accident (BA) was compared to the non-bicycle accident (NBA) group using linear and logistic regression  models, with correction for age and sex. RESULTS: Of the 875 patients included, 102 (11.7%) had a bicycle accident. BA patients were younger (79.8 versus 83.9 years, p < 0.001), less often female (54.9 versus 71.2%, p = 0.001) and lived independently more often (100 versus 85.1%, p < 0.001). Median LOS in the BA group was 0.91 times the median LOS in the NBA group (p = 0.125). For none of the secondary outcomes the odds ratio favored the BA group, except for infection during hospital stay (OR = 0.53, 95%CI 0.28-0.99; p = 0.048). CONCLUSIONS: Although older hip fracture patients who had a bicycle accident appeared more healthy than other older hip fracture patients, their clinical course was not more favorable. Based on this study, a bicycle accident is not an indicator that geriatric co-management can be omitted.

Factors Affecting Hospital Length of Stay in Geriatric Patients With a Surgically Treated Fragility Ankle Fracture.

Fragility ankle fractures in elderly have a rising incidence and hospitalization may be prolonged due to pre-existing comorbidities, compromised soft tissue and postoperative difficulties in the rehabilitation process. The aim of this retrospective cohort study was to investigate risk factors for longer total hospitalization duration in elderly patients with surgically treated fragility (Lauge Hansen supination external rotation type 4) fractures. We included all patients ≥ 70 years with a fragility fracture, who were treated surgically between 2011 and 2019 (n = 97) in a level 1 and 2 trauma center. Data on patient demographics, fracture characteristics, surgical treatment strategies and postoperative complications were retrieved from medical records. Multivariate regression analysis was performed to identify independent risk factors for longer hospitalization duration. The mean age of the included patients was 78.27 (± 6.56) years; 71 patients (73.20%) were female. Ten fractures (10.30%) were classified as open and 49 (50.50%) as a luxation type fracture. Fifty-nine patients (60.80%) were hospitalized after admission to the emergency department. External fixation was performed in 34 patients (35.10%) and served as bridge to definitive fixation in 29 patients (85.30%). The mean total hospital length of stay of all patients was 7.04 (± 6.58) days. Multivariate regression analysis demonstrated that the use of external fixation (p < .001) and the postoperative discharge destination (p < .001) were independently associated with a prolonged hospital stay. External fixation and discharge destination were independent risk factors for a prolonged hospital stay in elderly patients with a fragility fracture.

Postoperative Complications of Minimally Invasive Intramedullary Nail Fixation Versus Plate Fixation for Distal Fibular Fractures in Elderly Patients: A Retrospective Double Cohort Study in a Geriatric Trauma Unit in the Netherlands.

Intramedullary fixation using a fibular nail is a minimally invasive alternative to conventional plate fixation that provides superior biomechanical strength and allows immediate full weightbearing postoperatively. The study aim was to compare the postoperative complications of minimally invasive intramedullary fibular nail fixation to plate fixation for Lauge-Hansen supination external rotation type 4 (Weber B) fractures in patients aged 65 years or older treated in a single geriatric trauma unit in the Netherlands. A retrospective cohort study was performed including patients aged 65 years or older with a Lauge-Hansen supination external rotation type 4 (Weber B) fracture treated with either intramedullary fibular fixation or plate fixation between January 2017 and January 2019. A total number of 58 patients were included with a mean age of 73.9 years (range 65-95). The intramedullary fixation-cohort (n = 13) had a significantly higher mean age (82.5 vs 71.4 years, p = .002) and Charlson Co-morbidity Index (4.7 vs 3.6, p = .005) compared to the plate fixation-cohort (n = 45). The total number of postoperative complications was lower after intramedullary fixation (n = 2, 15%) compared to plate fixation (n = 15, 33%), although this relative difference was not significant (p = .307). All 2 complications observed after intramedullary fixation were wound infections demanding no debridement or implant removal. No implant related complications, hospital-acquired complications or mortality were observed after intramedullary fixation. Despite the higher mean age and co-morbidity status of patients treated with minimally invasive intramedullary fibular nailing, the total number of postoperative complications was lower after intramedullary fixation compared to plate fixation. This technique might be a promising alternative in selected patients.

Minimally invasive double-plating osteosynthesis of the distal femur.

OBJECTIVE: Technical description of minimally invasive double-plating of the distal femur. INDICATIONS: Peri- and interprosthetic distal femur fractures with limited (periprosthetic) bone stock in geriatric patients. Re-operations (delayed and non-unions; infected non-unions) of the distal femur. Distal femoral fractures or femoral shaft fractures that do not qualify for femoral nailing and where the patient is unable to comply with weight-bearing restrictions. CONTRAINDICATIONS: Peri- and interprosthetic femoral fractures with unstable knee prosthesis and local soft tissue infection. Peri- and interprosthetic fractures of the proximal femur. SURGICAL TECHNIQUE: Supine position on a radiolucent table with both legs draped free. Support the knee to release traction on the distal fragment by the gastrocnemius muscle. Reduction and fixation of the fracture using a minimally invasive lateral approach. To reduce stress riser zones in interprosthetic fractures, the fixation device should overlap both the prosthesis by at least twice the diameter of the femoral diaphysis. Control plate position and reduction with special emphasis on length, rotation and longitudinal axes, using the healthy side as a reference. After sufficient reduction and fixation of the fracture, one proceeds to the medial plate fixation of the femur. Pre- or intraoperative contouring of a narrow large fragment locking compression plate into a helical shaped plate should be performed, using bending irons and a saw bone of a standard femur. The helical shaped plate is introduced submuscular and epiperiosteal in a minimally invasive fashion and fixed with bicortical locking screws. POSTOPERATIVE MANAGEMENT: Unrestricted weight bearing with walker or crutches under supervision of physiotherapist. RESULTS: Between 2015 and December 2018, minimally invasive double-plate osteosynthesis using a medial helical shaped plate was performed in 11 patients. In 6 cases it was applied in patients (81 years ± 7 SD) with a supracondylar peri- or interprosthetic femoral fracture. No implant failure or loss of reduction was seen after postoperative unrestricted weight bearing. In the additional 5 cases double-plating was used in salvage procedures ([infected] non-unions, hardware failure). One of these patients developed a fracture-related infection for which all material was removed. The fracture healed after a new attempt of antegrade nailing combined with an additional locking plate. In the remaining patients complete bone healing without hardware failure was seen.

Retrograde intramedullary nailing for humeral midshaft fractures : a retrospective cohort study.

This study evaluates the patient-reported functional outcome, clinical functional outcome and frequency of complications of simple oblique and transverse humeral midshaft fractures treated with a retrograde expert humeral nail. A retrospective cohort study of humeral midshaft fractures (AO 12-A2, 12-A3) treated with retrograde nailing between January 2010 and February 2018 in a level II trauma center was performed. Patients' perception of functional outcome was measured using the Disabilities of the Arm, Shoulder and Hand (DASH) scores. Thirteen patients with a median age of 20-years were treated with a retrograde nail. The median DASH score, administered 29 months (IQR 74) after surgery, was 7.9 (IQR 15.9). There were no perioperative frac- tures and the frequency of complications was 8%, being one nonunion. Retrograde nailing for humeral midshaft fractures is a safe technique, with excellent patient reported and clinical functional outcome. No iatrogenic peri- operative fractures occurred and the frequency of complications was low. We recommend the retrograde technique, if surgical fixation of humeral midshaft fractures is needed, especially in younger patients for who rotator cuff associated injuries will have a major impact on quality of life.

Intramedullary screw fixation for simple displaced olecranon fractures.

PURPOSE: Olecranon fractures are common and typically require surgical fixation due to displacement generated by the pull of the triceps muscle. The most common techniques for repairing olecranon fractures are tension-band wiring or plate fixation, but these methods are associated with high rates of implant-related soft-tissue irritation. Another treatment option is fixation with an intramedullary screw, but less is known about surgical results using this strategy. Thus, the purpose of this study was to report the clinical and functional outcomes of olecranon fractures treated with an intramedullary cannulated screw. METHODS: We identified 15 patients (average age at index procedure 44 years, range 16-83) with a Mayo type I or IIA olecranon fracture who were treated with an intramedullary cannulated screw at a single level 2 trauma center between 2012 and 2017. The medical record was reviewed to assess radiographic union, postoperative range of motion and complications (including hardware removal). Patient-reported outcome was evaluated using the Disabilities of the Arm, Shoulder and Hand (DASH) score. Average follow-up was 22 months (range 8-36 months). RESULTS: By the 6th month post-operative visit, 14 patients had complete union of their fracture and 1 patient had an asymptomatic non-union that did not require further intervention. Average flexion was 145° (range 135-160) and the average extension lag was 11° (range 0-30). Implants were removed in 5 patients due to soft-tissue irritation. Average DASH score (± standard deviation) by final follow-up was 16 ± 10. CONCLUSIONS: Fixation of simple olecranon fractures with an intramedullary screw is a safe and easy fixation method in young patients, leading to good functional and radiological results. Compared to available data, less hardware removal is necessary than with tension-band wiring or plate fixation.

Correction to: Intramedullary screw fixation for simple displaced olecranon fractures.

The original version of this article unfortunately contained some mistakes. The spelling of the Willem Maarten P. F. Bosmans' name was incorrect.

Surgical treatment of acute and chronic AC joint dislocations: Five-year experience with conventional and modified LARS fixation by a single surgeon.

BACKGROUND: Different surgical fixation methods are available for the treatment of acromioclavicular (AC) joint dislocations. The aim of this study was to present the results of five years of experience with the Ligament Augmentation and Reconstruction System (LARS) fixation technique by a single surgeon. METHODS: A single-center retrospective cohort study was performed. All patients treated for an AC joint dislocation with LARS fixation by the same surgeon between 2012 and 2016 (n = 20) were eligible for inclusion. All these dislocations were unstable injuries, Rockwood type-III or higher, requiring acute or chronic repair. The primary outcome was the QuickDASH score. Secondary outcomes were the Subjective Shoulder Value (SSV), Numerical Rating Scale (NRS) pain score, return to work, complications, and implant removal. RESULTS: 17 patients (85%) were available for final follow-up. The median follow-up was 23 months (IQR; 17─34). The median QuickDASH score was 7 (IQR; 2-18), the median SSV was 90 (IQR; 80-90), and the median NRS pain score was 2 (IQR; 1-3). Patients returned to work after a median of 8 weeks (IQR; 6-12). There was no significant difference in functional outcome scores between acute and chronic repair, or between the conventional and modified LARS fixation groups. There were two major complications requiring revision surgery, one ruptured LARS ligament and one case of deep wound infection. Implant removal was performed in one patient. CONCLUSIONS: The LARS ligament fixation technique seems to be effective for the treatment of AC joint dislocations, resulting in good short- and mid-term patient-reported functional outcome. LARS fixation might also be an acceptable treatment option for active patients with symptomatic chronic AC dislocations. LEVEL OF EVIDENCE: Level III, Retrospective Comparative Study, Treatment Study.

Intramedullary Fixation Versus Plate Fixation of Distal Fibular Fractures: A Systematic Review and Meta-Analysis of Randomized Controlled Trials and Observational Studies.

Intramedullary fixation (IMF) has been described as a minimally invasive alternative to open reduction and internal fixation for operative treatment of distal fibular fractures in case of compromised soft tissue or severe comorbidities. The objective was to compare postoperative complications and functional outcomes of intramedullary versus plate fixation (PF) in distal fibular fractures. A systematic review and meta-analysis was performed. The PubMed/MEDLINE, Embase, Cochrane, and CINAHL databases were searched for both randomized controlled trials and observational studies. A total of 26 studies was included, reporting on 1710 patients with a mean age of 51.6 years. Meta-analysis was performed on 8 comparative studies, including subgroup and sensitivity analyses on all outcomes. IMF was associated with significantly fewer wound related complications (odds ratio [OR], 0.11; 95% confidence interval [CI], 0.04 to 0.25; p < .01), implant removals (OR, 0.54; 95% CI, 0.31 to 0.93; p = .03), and nonunions (OR, 0.31; 95% CI, 0.15 to 0.62; p < .01). No differences were found regarding malunion (OR, 0.45; 95% CI, 0.17 to 1.21; p = .11) and the Olerud Molander Ankle Score for long-term functional outcome (mean difference, 9.56; 95% CI, 1.24 to 20.37; p = .08). Results of this study apply to a select group of patients, in which the advantages of minimal soft tissue damage by IMF are preferable to optimal fracture reduction by PF. IMF of distal fibular fractures resulted in fewer wound-related complications, implant removals, and nonunions compared with PF. Especially in elderly patients, patients with chronic comorbidity, and patients with compromised soft tissue, IMF may be preferred over PF.

[Complete triceps tendon rupture; a rare tendon injury]. / Complete tricepspeesruptuur.

Only 1% of all tendon injuries affect the triceps tendon, making triceps ruptures very rare. An acute rupture can therefore easily be missed due to a low degree of suspicion. A palpable gap, inability to flex the elbow against resistance and a positive modified Thompson test are indicative for a complete triceps tendon rupture. The mechanism of injury is most commonly a sudden eccentric muscle contraction. We present the case of a 48-year-old man with an acute complete triceps tendon rupture, after a fall from an unstable chair while performing a one arm push-up. The rupture was surgically treated with Krackow sutures tunneled through drill holes in the olecranon. Postoperative treatment consisted of gradually increasing elbow flexion for six weeks with a brace. Three months following the operation, 150 degree flexion was possible with a 5 degree extension limitation. The Disabilities of the Arm, Shoulder and Hand score was 10.5. We demonstrate that early diagnosis and treatment facilitate excellent functional outcome.

SIRT1/PGC1α-Dependent Increase in Oxidative Phosphorylation Supports Chemotherapy Resistance of Colon Cancer.

PURPOSE: Chemotherapy treatment of metastatic colon cancer ultimately fails due to development of drug resistance. Identification of chemotherapy-induced changes in tumor biology may provide insight into drug resistance mechanisms. EXPERIMENTAL DESIGN: We studied gene expression differences between groups of liver metastases that were exposed to preoperative chemotherapy or not. Multiple patient-derived colonosphere cultures were used to assess how chemotherapy alters energy metabolism by measuring mitochondrial biomass, oxygen consumption, and lactate production. Genetically manipulated colonosphere-initiated tumors were used to assess how altered energy metabolism affects chemotherapy efficacy. RESULTS: Gene ontology and pathway enrichment analysis revealed significant upregulation of genes involved in oxidative phosphorylation (OXPHOS) and mitochondrial biogenesis in metastases that were exposed to chemotherapy. This suggested chemotherapy induces a shift in tumor metabolism from glycolysis towards OXPHOS. Indeed, chemotreatment of patient-derived colonosphere cultures resulted in an increase of mitochondrial biomass, increased expression of respiratory chain enzymes, and higher rates of oxygen consumption. This was mediated by the histone deacetylase sirtuin-1 (SIRT1) and its substrate, the transcriptional coactivator PGC1α. Knockdown of SIRT1 or PGC1α prevented chemotherapy-induced OXPHOS and significantly sensitized patient-derived colonospheres as well as tumor xenografts to chemotherapy. CONCLUSIONS: Chemotherapy of colorectal tumors induces a SIRT1/PGC1α-dependent increase in OXPHOS that promotes tumor survival during treatment. This phenomenon is also observed in chemotherapy-exposed resected liver metastases, strongly suggesting that chemotherapy induces long-lasting changes in tumor metabolism that potentially interfere with drug efficacy. In conclusion, we propose a novel mechanism of chemotherapy resistance that may be clinically relevant and therapeutically exploitable.

Wnt signalling induces accumulation of phosphorylated ß-catenin in two distinct cytosolic complexes.

Wnt/ß-catenin signalling controls development and adult tissue homeostasis and causes cancer when inappropriately activated. In unstimulated cells, an Axin1-centred multi-protein complex phosphorylates the transcriptional co-activator ß-catenin, marking it for degradation. Wnt signalling antagonizes ß-catenin proteolysis, leading to its accumulation and target gene expression. How Wnt stimulation alters the size distribution, composition and activity of endogenous Axin1 complexes remains poorly understood. Here, we employed two-dimensional blue native/SDS-PAGE to analyse endogenous Axin1 and ß-catenin complexes during Wnt signalling. We show that the size range of Axin1 complexes is conserved between species and remains largely unaffected by Wnt stimulation. We detect a striking Wnt-dependent, cytosolic accumulation of both non-phosphorylated and phosphorylated ß-catenin within a 450 kDa Axin1-based complex and in a distinct, Axin1-free complex of 200 kDa. These results argue that during Wnt stimulation, phosphorylated ß-catenin is released from the Axin1 complex but fails to undergo immediate degradation. Importantly, in APC-mutant cancer cells, the distribution of Axin1 and ß-catenin complexes strongly resembles that of Wnt-stimulated cells. Our findings argue that Wnt signals and APC mutations interfere with the turnover of phosphorylated ß-catenin. Furthermore, our results suggest that the accumulation of small-sized ß-catenin complexes may serve as an indicator of Wnt pathway activity in primary cancer cells.

GPx2 suppression of H2O2 stress links the formation of differentiated tumor mass to metastatic capacity in colorectal cancer.

Colorectal tumorigenesis is accompanied by the generation of oxidative stress, but how this controls tumor development is poorly understood. Here, we studied how the H2O2-reducing enzyme glutathione peroxidase 2 (GPx2) regulates H2O2 stress and differentiation in patient-derived "colonosphere" cultures. GPx2 silencing caused accumulation of radical oxygen species, sensitization to H2O2-induced apoptosis, and strongly reduced clone- and metastasis-forming capacity. Neutralization of radical oxygen species restored clonogenic capacity. Surprisingly, GPx2-suppressed cells also lacked differentiation potential and formed slow-growing undifferentiated tumors. GPx2 overexpression stimulated multilineage differentiation, proliferation, and tumor growth without reducing the tumor-initiating capacity. Finally, GPx2 expression was inversely correlated with H2O2-stress signatures in human colon tumor cohorts, but positively correlated with differentiation and proliferation. Moreover, high GPx2 expression was associated with early tumor recurrence, particularly in the recently identified aggressive subtype of human colon cancer. We conclude that H2O2 neutralization by GPx2 is essential for maintaining clonogenic and metastatic capacity, but also for the generation of differentiated proliferating tumor mass. The results reveal an unexpected redox-controlled link between tumor mass formation and metastatic capacity.

Hypoxia after liver surgery imposes an aggressive cancer stem cell phenotype on residual tumor cells.

OBJECTIVE: To assess the contribution of hypoxia and bone marrow-derived cells to aggressive outgrowth of micrometastases after liver surgery. BACKGROUND: Liver surgery generates a microenvironment that fosters aggressive tumor recurrence. These areas are characterized by chronic hypoxia and influx of bone marrow-derived cells. METHODS: The contribution of hematopoietic cell types was studied in mice lacking specific components of the immune system and in irradiated mice lacking all bone marrow-derived cells. Tumor cells were derived from colorectal cancer patients and from a metastatic tumor cell line. Hypoxia-induced changes in stem cell and differentiation marker expression, clone-forming potential, and metastatic capacity were assessed. The effect of vascular clamping on cancer stem cell (CSC) characteristics was performed in mice bearing patient-derived liver metastases. RESULTS: Immune cells and bone marrow-derived cells were not required for aggressive outgrowth of micrometastases in livers treated with surgery. Rather, hypoxia was sufficient to promote invasion and accelerate metastatic outgrowth. This was associated with a rapid loss of differentiation markers and increased expression of CSC markers and clone-forming capacity. Likewise, metastases residing in ischemia-reperfusion-injured liver lobes acquired CSC characteristics. Despite their renowned general resistance to chemotherapy, clone-forming CSCs were readily killed by the hypoxia-activated prodrug tirapazamine. CONCLUSIONS: Surgery-generated hypoxia in the liver causes rapid dedifferentiation of tumor cells into immature CSCs with high clone- and metastasis-forming capacity. The results help explain the phenomenon of aggressive local tumor recurrence after liver surgery and offer a potential strategy to kill aggressive CSCs by hypoxia-activated prodrugs.

The secretome of colon cancer stem cells contains drug-metabolizing enzymes.

Drug-resistant cancer stem cells (CSCs) have been implicated in tumor recurrence following chemotherapy. However, the contribution of CSCs to drug-resistance in colorectal cancer is unclear and CSC-intrinsic drug-resistance mechanisms are ill-defined. Here, we address these issues by proteomic analysis of the secretomes of CSCs and isogenic differentiated tumor cells (DTCs) isolated from three distinct metastasized colon tumors. Mass spectrometry-based proteomics identified 1254 unique proteins in the conditioned media of the paired CSC and DTC cultures. Ingenuity Pathway Analysis revealed that proteins governing 'Cell Death' were most significantly enriched in the CSC secretome. The vast majority of these (37/43) promote cell survival. The CSC secretome is also characterized by a pro-survival Nrf2 antioxidant signature. Interestingly, proteome-maintenance networks are highly enriched in the CSC secretome. CSCs also secrete high levels of drug-metabolizing enzymes, including aldehyde dehydrogenase 1 (ALDH1A1) and bleomycin hydrolase (BLMH). We show that these enzymes cause extracellular detoxification of maphosphamide and bleomycin respectively. We conclude that colorectal CSCs are characterized by extensive survival and anti-oxidant networks, which are likely to contribute to CSC-intrinsic drug-resistance. In addition, CSCs may modulate drug responses in nearby tumor cells by detoxifying chemotherapeutic drugs in the extracellular space. BIOLOGICAL SIGNIFICANCE: Cancer stem cells are thought to play an important role in mediating drug resistance and tumor recurrence following chemotherapy. Therefore, it is important to identify the factors that are secreted by them. Our results provide novel insights into the pathways that govern the intrinsic resistance of CSCs to chemotherapy and, furthermore, demonstrate that they can also inactivate chemotherapeutic drugs in the extracellular space. A better understanding of the pathways that govern drug resistance in CSCs may help in developing effective CSC-targeting drugs.

Inertial focusing for tumor antigen-dependent and -independent sorting of rare circulating tumor cells.

Circulating tumor cells (CTCs) are shed into the bloodstream from primary and metastatic tumor deposits. Their isolation and analysis hold great promise for the early detection of invasive cancer and the management of advanced disease, but technological hurdles have limited their broad clinical utility. We describe an inertial focusing-enhanced microfluidic CTC capture platform, termed "CTC-iChip," that is capable of sorting rare CTCs from whole blood at 10(7) cells/s. Most importantly, the iChip is capable of isolating CTCs using strategies that are either dependent or independent of tumor membrane epitopes, and thus applicable to virtually all cancers. We specifically demonstrate the use of the iChip in an expanded set of both epithelial and nonepithelial cancers including lung, prostate, pancreas, breast, and melanoma. The sorting of CTCs as unfixed cells in solution allows for the application of high-quality clinically standardized morphological and immunohistochemical analyses, as well as RNA-based single-cell molecular characterization. The combination of an unbiased, broadly applicable, high-throughput, and automatable rare cell sorting technology with generally accepted molecular assays and cytology standards will enable the integration of CTC-based diagnostics into the clinical management of cancer.

PDGFRB promotes liver metastasis formation of mesenchymal-like colorectal tumor cells.

In epithelial tumors, the platelet-derived growth factor receptor B (PDGFRB) is mainly expressed by stromal cells of mesenchymal origin. Tumor cells may also acquire PDGFRB expression following epithelial-to-mesenchymal transition (EMT), which occurs during metastasis formation. Little is known about PDGFRB signaling in colorectal tumor cells. We studied the relationship between PDGFRB expression, EMT, and metastasis in human colorectal cancer (CRC) cohorts by analysis of gene expression profiles. PDGFRB expression in primary CRC was correlated with short disease-free and overall survival. PDGFRB was co-expressed with genes involved in platelet activation, transforming growth factor beta (TGFB) signaling, and EMT in three CRC cohorts. PDGFRB was expressed in mesenchymal-like tumor cell lines in vitro and stimulated invasion and liver metastasis formation in mice. Platelets, a major source of PDGF, preferentially bound to tumor cells in a non-activated state. Platelet activation caused robust PDGFRB tyrosine phosphorylation on tumor cells in vitro and in liver sinusoids in vivo. Platelets also release TGFB, which is a potent inducer of EMT. Inhibition of TGFB signaling in tumor cells caused partial reversion of the mesenchymal phenotype and strongly reduced PDGFRB expression and PDGF-stimulated tumor cell invasion. These results suggest that PDGFRB may contribute to the aggressive phenotype of colorectal tumors with mesenchymal properties, most likely downstream of platelet activation and TGFB signaling.

Proteomics in studying cancer stem cell biology.

Normal multipotent tissue stem cells (SCs) are the driving force behind tissue turnover and repair. The cancer stem cell theory holds that tumors also contain stem-like cells that drive tumor growth and metastasis formation. However, very little is known about the regulation of SC maintenance pathways in cancer and how these are affected by cancer-specific genetic alterations and by treatment. Proteomics is emerging as a powerful tool to identify the signaling complexes and pathways that control multi- and pluri-potency and SC differentiation. Here, the authors review the novel insights that these studies have provided and present a comprehensive strategy for the use of proteomics in studying cancer SC biology.

The death receptor CD95 activates the cofilin pathway to stimulate tumour cell invasion.

The death receptor CD95 promotes apoptosis through well-defined signalling pathways. In colorectal cancer cells, CD95 primarily stimulates migration and invasion through pathways that are incompletely understood. Here, we identify a new CD95-activated tyrosine kinase pathway that is essential for CD95-stimulated tumour cell invasion. We show that CD95 promotes Tyr 783 phosphorylation of phospholipase C-γ1 through the platelet-derived growth factor receptor-ß, resulting in ligand-stimulated phosphatidylinositol (4,5)-bisphosphate (PIP(2)) hydrolysis. PIP(2) hydrolysis liberates the actin-severing protein cofilin from the plasma membrane to initiate cortical actin remodelling. Cofilin activation is required for CD95-stimulated formation of membrane protrusions and increased tumour cell invasion.

Differentiated human colorectal cancer cells protect tumor-initiating cells from irinotecan.

BACKGROUND & AIMS: Stem cells of normal tissues have resistance mechanisms that allow them to survive genotoxic insults. The stem cell-like cells of tumors are defined by their tumor-initiating capacity and may have retained these resistance mechanisms, making them resistant to chemotherapy. We studied the relationship between resistance to the topoisomerase I inhibitor irinotecan and tumor-initiating potential in human colonosphere cultures and in mice with colorectal xenograft tumors. METHODS: Colonosphere cultures were established from human colorectal tumor specimens obtained from patients who underwent colon or liver resection for primary or metastatic adenocarcinoma. Stem cell and differentiation markers were analyzed by immunoblotting and fluorescence-activated cell sorting. Clone- and tumor-initiating capacities were assessed by single-cell cloning and in immune-deficient mice. Sensitivity to irinotecan was assessed in vitro and in tumor-bearing mice. The relationship between drug resistance and tumor-initiating capacity was tested by fluorescence-activated cell sorting of colonosphere cells, based on expression of ABCB1 and aldehyde dehydrogenase (ALDH) activity. RESULTS: Colonosphere cultures had a high capacity to initiate tumors in mice and were resistant to irinotecan. Inhibition of the drug-efflux pump ABCB1 by PSC-833 allowed irinotecan to eradicate tumor-initiating cells. However, ABCB1 was expressed only by a subpopulation of differentiated tumor cells that did not form clones or tumors. Conversely, tumor-initiating cells were ABCB1-negative and were identified by high ALDH activity. Tumorigenic ALDHhigh/ABCB1negative cells generated nontumorigenic ALDHlow/ABCB1positive daughter cells in vitro and in tumor xenografts. PSC-833 increased the antitumor efficacy of irinotecan in mice. CONCLUSIONS: The resistance of colorectal tumors to irinotecan requires the cooperative action of tumor-initiating ALDHhigh/ABCB1negative cells and their differentiated, drug-expelling, ALDHlow/ABCB1positive daughter cells.