Unveiling acquired resistance to anti-EGFR therapies in colorectal cancer: a long and winding road

Emergence of acquired resistance limits the efficacy of the anti-EGFR therapies cetuximab and panitumumab in metastatic colorectal cancer. In the last decade, preclinical and clinical cohort studies have uncovered genomic alterations that confer a selective advantage to tumor cells under EGFR blockade, mainly downstream re-activation of RAS-MEK signaling and mutations in the extracellular domain of EGFR (EGFR-ECD). Liquid biopsies (genotyping of ctDNA) have been established as an excellent tool to easily monitor the dynamics of genomic alterations resistance in the blood of patients and to select patients for rechallenge with anti-EGFR therapies. Accordingly, several clinical trials have shown clinical benefit of rechallenge with anti-EGFR therapy in genomically-selected patients using ctDNA. However, alternative mechanisms underpinning resistance beyond genomics -mainly related to the tumor microenvironment-have been unveiled, specifically relevant in patients receiving chemotherapy-based multi-drug treatment in first line. This review explores the complexity of the multifaceted mechanisms that mediate secondary resistance to anti-EGFR therapies and potential therapeutic strategies to circumvent acquired resistance.

The prognostic potential of CDX2 in colorectal cancer: Harmonizing biology and clinical practice

Adjuvant chemotherapy following surgical intervention remains the primary treatment option for patients with localized colorectal cancer (CRC). However, a significant proportion of patients will have an unfavorable outcome after current forms of chemotherapy. While reflecting the increasing complexity of CRC, the clinical application of molecular biomarkers provides information that can be utilized to guide therapeutic strategies. Among these, caudal-related homeobox transcription factor 2 (CDX2) emerges as a biomarker of both prognosis and relapse after therapy. CDX2 is a key transcription factor that controls intestinal fate. Although rarely mutated in CRC, loss of CDX2 expression has been reported mostly in right-sided, microsatellite-unstable tumors and is associated with aggressive carcinomas. The pathological assessment of CDX2 by immunohistochemistry can thus identify patients with high-risk CRC, but the evaluation of CDX2 expression remains challenging in a substantial proportion of patients. In this review, we discuss the roles of CDX2 in homeostasis and CRC and the alterations that lead to protein expression loss. Furthermore, we review the clinical significance of CDX2 assessment, with a particular focus on its current use as a biomarker for pathological evaluation and clinical decision-making. Finally, we attempt to clarify the molecular implications of CDX2 deficiency, ultimately providing insights for a more precise evaluation of CDX2 protein expression.

Peptide-Platinum(IV) Conjugation Minimizes the Negative Impact of Current Anticancer Chemotherapy on Nonmalignant Cells

The relative success of platinum (Pt)-based chemotherapy comes at the cost of severe adverse side effects and is associated with a high risk of pro-oncogenic activation in the tumor microenvironment. Here, we report the synthesis of C-POC, a novel Pt(IV) cell-penetrating peptide conjugate showing a reduced impact against nonmalignant cells. In vitro and in vivo evaluation using patient-derived tumor organoids and laser ablation inductively coupled plasma mass spectrometry indicates that C-POC maintains robust anticancer efficacy while displaying diminished accumulation in healthy organs and reduced adverse toxicity compared to the standard Pt-based therapy. Likewise, C-POC uptake is significantly lowered in the noncancerous cells populating the tumor microenvironment. This results in the downregulation of versican, a biomarker of metastatic spreading and chemoresistance that we found upregulated in patients treated with standard Pt-based therapy. Altogether, our findings underscore the importance of considering the off-target impact of anticancer treatment on normal cells to improve drug development and patient care.

Determinants and Functions of CAFs Secretome During Cancer Progression and Therapy

Multiple lines of evidence are indicating that cancer development and malignant progression are not exclusively epithelial cancer cell-autonomous processes but may also depend on crosstalk with the surrounding tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs) are abundantly represented in the TME and are continuously interacting with cancer cells. CAFs are regulating key mechanisms during progression to metastasis and response to treatment by enhancing cancer cells survival and aggressiveness. The latest advances in CAFs biology are pointing to CAFs-secreted factors as druggable targets and companion tools for cancer diagnosis and prognosis. Especially, extensive research conducted in the recent years has underscored the potential of several cytokines as actionable biomarkers that are currently evaluated in the clinical setting. In this review, we explore the current understanding of CAFs secretome determinants and functions to discuss their clinical implication in oncology.

Minimal Residual Disease, Metastasis and Immunity

Progression from localized to metastatic disease requires cancer cells spreading to distant organs through the bloodstream. Only a small proportion of these circulating tumor cells (CTCs) survives dissemination due to anoikis, shear forces and elimination by the immune system. However, all metastases originate from CTCs capable of surviving and extravasating into distant tissue to re-initiate a tumor. Metastasis initiation is not always immediate as disseminated tumor cells (DTCs) may enter a non-dividing state of cell dormancy. Cancer dormancy is a reversible condition that can be maintained for many years without being clinically detectable. Subsequently, late disease relapses are thought to be due to cancer cells ultimately escaping from dormant state. Cancer dormancy is usually associated with minimal residual disease (MRD), where DTCs persist after intended curative therapy. Thus, MRD is commonly regarded as an indicator of poor prognosis in all cancers. In this review, we examine the current understanding of MRD and immunity during cancer progression to metastasis and discuss clinical perspectives for oncology.

Reproducibility of Histopathologic Diagnosis and Classification of Non-Melanocytic Skin Cancer: A Panel Exercise in the Framework of the Multicenter Southern European Study Helios

Aims and background

The reproducibility of histologic diagnoses, and in particular of the distinction between basal and squamous cell forms, has been evaluated in the framework of a multicenter case-control study (in Italy, France, Spain and Switzerland) aimed to assess the causes of non-melanocytic skin cancers.

Methods

A panel composed of 10 pathologists from the collaborating centers was appointed. A total of 1774 slides of routine diagnoses were blindly reviewed by a second panelist; discordant diagnoses underwent a third examination. Controversial and interesting cases were discussed during general sessions.

Results

The results showed a high degree of concordance (99.5%), with a Cohen's kappa of 0.85 (95% CI, 0.77–0.94) in the assessment of malignancy of lesions. The concordance in the distinction between large morphologic groups, basal cell carcinoma and squamous cell carcinoma was also high (Cohen's kappa = 0.85; 95% CI, 0.82–0.89). The assessment of histologic subtypes, degree of invasion and differentiation showed a lower degree of concordance, presumably as a consequence of a weaker consistency in the relevant classifications.

Conclusions

The reproducibility study has therefore validated the epidemiologic study and in particular allowed to correct some misclassifications that could have lessened the analysis of the case-control study. In general, because of its characteristics (number of pathologists and variety of their origins, the large number of cases examined, blind examination of histologic slides), the conclusions of the study may show a certain degree of generalization, at least with regard to the countries represented. Routine histologic diagnoses of cutaneous carcinoma showed a high degree of reliability with reference to the assessment of malignancy and the distinction between basal and squamous cell carcinoma morphotypes.

Intratumoural evolutionary landscape of high-risk prostate cancer: the PROGENY study of genomic and immune parameters

BACKGROUND

Intratumoural heterogeneity (ITH) is well recognised in prostate cancer (PC), but its role in high-risk disease is uncertain. A prospective, single-arm, translational study using targeted multiregion prostate biopsies was carried out to study genomic and T-cell ITH in clinically high-risk PC aiming to identify drivers and potential therapeutic strategies.

PATIENTS AND METHODS

Forty-nine men with elevated prostate-specific antigen and multiparametric-magnetic resonance imaging detected PC underwent image-guided multiregion transperineal biopsy. Seventy-nine tumour regions from 25 patients with PC underwent sequencing, analysis of mutations, copy number and neoepitopes combined with tumour infiltrating T-cell subset quantification.

RESULTS

We demonstrated extensive somatic nucleotide variation and somatic copy number alteration heterogeneity in high-risk PC. Overall, the mutational burden was low (0.93/Megabase), but two patients had hypermutation, with loss of mismatch repair (MMR) proteins, MSH2 and MSH6. Somatic copy number alteration burden was higher in patients with metastatic hormone-naive PC (mHNPC) than in those with high-risk localised PC (hrlPC), independent of Gleason grade. Mutations were rarely ubiquitous and mutational frequencies were similar for mHNPC and hrlPC patients. Enrichment of focal 3q26.2 and 3q21.3, regions containing putative metastasis drivers, was seen in mHNPC patients. We found evidence of parallel evolution with three separate clones containing activating mutations of β-catenin in a single patient. We demonstrated extensive intratumoural and intertumoural T-cell heterogeneity and high inflammatory infiltrate in the MMR-deficient (MMRD) patients and the patient with parallel evolution of β-catenin. Analysis of all patients with activating Wnt/β-catenin mutations demonstrated a low CD8+/FOXP3+ ratio, a potential surrogate marker of immune evasion.

CONCLUSIONS

The PROGENY (PROstate cancer GENomic heterogeneitY) study provides a diagnostic platform suitable for studying tumour ITH. Genetic aberrations in clinically high-risk PC are associated with altered patterns of immune infiltrate in tumours. Activating mutations of Wnt/β-catenin signalling pathway or MMRD could be considered as potential biomarkers for immunomodulation therapies.

CLINICAL TRIALS.GOV IDENTIFIER

NCT02022371.

Effects of nanocrystalline hydroxyapatites on macrophage polarization

Silicon substituted and nanocrystalline hydroxyapatites have attracted the attention of many researchers due to their up-regulation in osteoblast cell metabolism and enhanced bioreactivity, respectively. On the other hand, the biomaterial success or failure depends ultimately on the immune response triggered after its implantation. Macrophages are the main components of the innate immune system with an important role in healing and tissue remodelling due to their remarkable functional plasticity, existing in a whole spectrum of functional populations with varying phenotypic features. The effects of nanocrystalline hydroxyapatite (nano-HA) and nanocrystalline silicon substituted hydroxyapatite (nano-SiHA) on the macrophage populations defined as pro-inflammatory (M1) and reparative (M2) phenotypes have been evaluated in the present study using RAW 264.7 cells and mouse peritoneal macrophages as in vitro models. M1 and M2 macrophage phenotypes were characterized by flow cytometry and confocal microscopy by the expression of CD80 and CD163, known as M1 and M2 markers, respectively. The polarization of primary macrophages towards the M1 or M2 phenotype was induced with the pro-inflammatory stimulus LPS or the anti-inflammatory stimulus IL-10, respectively, evaluating the biomaterial effects under these conditions. Our results show that both nano-HA and nano-SiHA favour the macrophage polarization towards an M2 reparative phenotype, decreasing M1 population and ensuring an appropriate response in the implantation site of these biomaterials designed for bone repair and bone tissue engineering.

In vitro evaluation of graphene oxide nanosheets on immune function

HYPOTHESIS

Graphene oxide (GO) has attracted the scientific community attention due to its novel properties and wide range of potential applications including hyperthermia cancer therapy. However, little is known about the GO effects on the immune function which involves both innate and adaptive defence mechanisms through the activation of different cell populations and secretion of several cytokines. The effect of different GO nanosheets designed for hyperthermia cancer therapy on macrophage and lymphocyte function should be determined before using GO for this application.

EXPERIMENTS

The effects of GO nanosheets with 1 (1-GOs) and 6 arms (6-GOs) of polyethylene glycol on RAW-264.7 macrophages and primary splenocytes (as approximation to the in vivo situation) were evaluated through the proinflammatory cytokine secretion and the modulation of cell proliferation in the presence of specific stimuli for either T-lymphocytes (concanavalin A, anti-CD3 antibody) or B-lymphocytes/macrophages (lipopolysaccharide).

FINDINGS

6-GOs significantly increased the secretion of TNF-α by RAW-264.7 macrophages without alteration of IL-6 and IL-1β levels. The treatment of primary splenocytes with 1-GOs and 6-GOs in the presence of concanavalin A, anti-CD3 antibody and lipopolysaccharide, produced significant dose-dependent decreases of cell proliferation and IL-6 levels, revealing weak inflammatory properties of GOs which are favourable for hyperthermia cancer therapy.

Triggering cell death by nanographene oxide mediated hyperthermia

Graphene oxide (GO) has been proposed as an hyperthermia agent for anticancer therapies due to its near-infrared (NIR) optical absorption ability which, with its small two-dimensional size, could have a unique performance when compared to that of any other nanoparticle. Nevertheless, attention should be given to the hyperthermia route and the kind of GO-cell interactions induced in the process. The hyperthermia laser irradiation parameters, such as exposure time and laser power, were investigated to control the temperature rise and consequent damage in the GOs containing cell culture medium. The type of cell damage produced was evaluated as a function of these parameters. The results showed that cell culture temperature (after irradiating cells with internalized GO) increases preferentially with laser power rather than with exposure time. Moreover, when laser power is increased, necrosis is the preferential cell death leading to an increase of cytokine release to the medium.

Análisis comparativo de las características neuropsicológicas de pacientes con demencia fronto-temporal, variante conductual y enfermedad de Alzheimer

Objetivo: Describir las características neuropsicológicas de pacientes con demencia frontotemporal varianteconductual (DFTvc) y compararlas con las de pacientes con enfermedad de Alzheimer (EA). Pacientes y métodos:Se evaluó una muestra de 60 controles sanos, 60 pacientes con EA y 32 pacientes con DFTvc, empleando una bateríaneuropsicológica clásica. Resultados: Los pacientes con DFTvc tienen peor rendimiento que pacientes con EA enalgunos parámetros de atención y funciones ejecutivas (FE) y menor compromiso de la memoria. La evaluaciónde atención muestra diferencia altamente significativa en el rendimiento del Trail Making Test (TMT)-A entre EAy DFTvc (t28=-2,18, p<0,001). De la misma manera, en la evaluación de FE, sólo el TMT-B (t31= -6,8, p<0,001) ylas respuestas perseverativas en el Wisconsin Card Sorting Test (WCST) (U = 30,5, p<0,001) alcanzaron diferenciaestadísticamente significativa entre los grupos EA y DFTvc. Conclusiones: Los pacientes con DFTvc en estadiosleve a moderado presentan una relativa menor afectación de memoria, lenguaje y habilidades viso-constructivas/viso-espaciales, pero con un marcado deterioro de atención y FE.

Cortisol hyporesponsiveness to the low dose ACTH test is a frequent finding in a pediatric population with type 1 diabetes mellitus

INTRODUCTION

In adults with type 1 diabetes mellitus (DM1), a 25% of risk of hypocortisolism has been found through a low dose ACTH test with negative antibodies suggesting other causes of hypothalamic-pituitary-adrenal axis dysfunction.

AIM

To evaluate adrenal function in pediatric patients with DM1 and correlate the results with the frequency of hypoglycemia and metabolic control.

METHODS

Sixty-nine patients were enrolled, age 12.3 (5.7-18.1); 50 boys and 19 girls. A 20% had additional autoimmune diseases. Mean hemoglobin A1c (HbA1c) was 8.1% and insulin dose was 1.14 U/kg/d. After an overnight fast, a low dose ACTH test (1 µg) was performed. Basal and stimulated cortisol concentrations, DHEAS, and plasma renin activity (PRA) were measured. A cortisol response post-ACTH below 18 µg/dL was considered abnormal.

RESULTS

58% of the tested patients had an abnormal response to ACTH test. These patients also had lower DHEAS concentrations, but were not different in diabetes duration, HbA1C, severe hypoglycemia, ACTH, or PRA concentrations compared to those who had a normal cortisol post-ACTH. One patient out of 59, had a positive anti-21-hydroxylase antibody (21OHA) and presented a poor response to ACTH.

CONCLUSIONS

We found a significant proportion of our patients having a subnormal cortisol response independent of the presence of anti-adrenal cell antibodies. We did not find a correlation with metabolic control, probably due to the good metabolic control of this group. The absence of 21OHA does not rule out subclinical hypocortisolism in this population. Our results suggest testing adrenal function in children with DM1.

Methicillin-susceptible Staphylococcus aureus clone related to the early pandemic phage type 80/81 causing an outbreak among residents of three occupational centres in Barcelona, Spain

In the 1950s an unusually virulent and transmissible penicillin-resistant Staphylococcus aureus clone harbouring Panton-Valentine leukocidin (PVL) genes, known as phage type 80/81 and subsequently identified as multilocus sequence type (ST) 30, emerged and caused serious infections in hospitals and the community. We describe an outbreak of skin infections caused by a PVL-positive, methicillin-susceptible S. aureus (MSSA) strain of ST1472, related to phage type 80/81, in three associated occupational centres. After identification of the first patient an active case-finding strategy was initiated among the three centres. Epidemiological and clinical features were indistinguishable from outbreaks currently caused by community-acquired methicillin-resistant S. aureus. The S. aureus was cultured and identified from nasal swabs and skin lesions by conventional methods; PVL was detected using a PCR assay. Pulsed-field gel electrophoresis and DNA-array-based genotyping were applied to MSSA isolates. MSSA was identified in nasal swabs from 49 of 133 individuals (37%). A single pulsed-field gel electrophoresis pattern, belonging to ST1472 (CC30) and PVL positivity, were detected in 20 individuals, including eight of 18 skin cultures, i.e. 15% of the screened individuals were colonized by the epidemic strain. Nasal and cutaneous decontamination with 5% nasal mupirocin ointment and 2% aqueous chlorhexidine was implemented for all individuals. Patients with active skin infections were treated with a first-generation cephalosporin. General recommendations were made to prevent cross-transmission. No new cases were reported over the following 90 days.

A positive association of peripheral arterial occlusive disease (PAD) andChlamydophila (Clamydia) pneumoniae

The relationship between Chlamydophila pneumoniae (Cp) infection and peripheral arterial occlusive disease (PAD) was studied by analyzing clinical samples from 95 patients with PAD and 100 controls. The following investigations were conducted: IgG and IgA against lipopolysaccharide (LPS) and against purified Cp-specific antigens from elementary bodies (EB) with ELISA; anti-EB IgG, with MIF; Cp DNA in arterial biopsy and peripheral blood mononuclear cells with heminested PCR; LPS with ELISA; and bacteria culture in HEp-2 cells from arterial biopsy. A significantly higher ratio of anti-EB IgG was detected in patients. There were no significant differences in anti-LPS IgG, anti-LPS IgA and anti-EB IgA between cases and controls. Cp DNA findings in the vascular wall biopsy showed significant differences between cases and controls. We obtained results that significantly involve Cp infection with PAD through the detection of anti-EB IgG from serum and bacterial DNA from arterial biopsy.

Role of apolipoprotein E epsilon 4 allele on chronic allograft nephropathy after renal transplantation

Lipid abnormalities may contribute to chronic allograft nephropathy (CAN). Apolipoprotein E (ApoE) gene polymorphism regulates lipoprotein metabolism, but little is known about an association between CAN and this polymorphism. The ApoE gene (E3/E4) polymorphism was typed by PCR assay (99 E3/E3, 28 E3/E4, 1 E4/E4) on 128 consecutive renal transplant patients with functioning grafts for more than 3 years (6.7 +/- 2.8 years). Twenty-eight patients with histological CAN were compared with 100 patients who had no clinical evidence of chronic rejection (no proteinuria and sCr < 2.5 mg%). As expected, univariate analysis revealed that patients with CAN experienced a greater acute rejection rate (78% vs 21%; P=.001), a higher serum creatinine (3.6 +/- 1.7 vs 1.4 +/- 0.5 mg%; P=.0001), and an older organ donor (43 +/- 20 vs 29 +/- 13 years; P=.0001). The lipid profiles (total cholesterol and triglycerides levels) were similar in both groups with 60% in each group receiving anti-lipemic drugs. Interestingly, the ApoE epsilon 4 allele was overrepresented in the group with CAN (39% vs 17%, P=.019). Logistic regression analysis showed that the epsilon 4 allele was an independent predictor of CAN (OR: 3.4; CI 95%: 1.07 to 11; P=.040) as were donor age and acute rejection episodes. In conclusion, an interaction between risk factors and genetic factors may determine CAN in this population. This finding may help to target prophylactic interventions in these recipients.

A new microimmunofluorescence test for the detection ofChlamydia pneumoniae specific antibodies

To evaluate a microimmunofluorescence (MIF) test (Chlamydia pneumoniae IgG, Vircell, Spain) that detects IgG against Chlamydophila pneumoniae (Cp), MRL Diagnostics MIF was used as reference test. Cross-reactivity against Chlamydia trachomatis (Ct) and Chlamydophila psittaci (Cps) was investigated. Eighty sera were analysed from 22 subjects with vascular disease, 38 with multiple sclerosis and 20 healthy individuals. Vircell and MRL MIF tests assessed 58.75% and 60% of the samples as positive, respectively, and their results coincided (positive/negative) in 98.75% of samples. One major (>1 IgG titre) and 32 minor (1 titre) discrepancies were observed. Correlation between tests was significant. Vircell MIF test demonstrated 97.9% sensitivity and 100% specificity. Differences in simultaneous reactivity to Ct and Cps between the tests were not significant. Vircell MIF test showed a good performance to detect the IgG against Cp.

Regression of left ventricular hypertrophy by lisinopril after renal transplantation: role of ACE gene polymorphism

BACKGROUND

Cardiac complications are the main cause of death in renal transplantation (RT), and left ventricular hypertrophy (LVH) may play an important role in these patients. The unfavorable genotype of the angiotensin-converting enzyme (ACE) gene has been associated with cardiovascular disease, including LVH. ACE inhibitors (ACEIs) reduce LVH, but little is known about the effects of ACEIs on LVH in RT patients with different insertion/deletion (I/D) genotypes of the ACE gene.

METHODS

We prospectively studied 57 stable nondiabetic RT patients with hypertension and echocardiographic LVH as well as a functional graft for 69.5 +/- 5.6 months. Patients randomly received either lisinopril 10 mg/day (group A, N = 29; 5 were excluded due to reversible acute renal failure) or placebo (group B, N = 28) for 12 months. Echocardiography (M-mode, 2-B, and color flow Doppler) was performed at baseline and 6 and 12 months later by the same examiner without previous knowledge of the genetic typing. The ACE genotype (I or D alleles) was ascertained by polymerase chain reaction (PCR; group A, DD = 10 and ID/II = 14; group B, DD = 15 and ID/II = 13).

RESULTS

All patients maintained a good renal function (serum creatinine <2.5 mg/dL) during the follow-up and both groups received a similar proportion of antihypertensive drugs (beta-blockers 83 vs. 79%; Ca antagonists 66 vs. 68%; alpha1-adrenoreceptor antagonists 50 vs. 67%) during the study. As expected, mean arterial blood pressure and hemoglobin levels showed a higher percentage reduction in group A versus group B (-4 +/- 2.8 vs. 2.1 +/- 2.6%, P = 0.07, and -11.5 +/- 1.5 vs. -0.5 +/- 2.3%, P < 0.01, respectively). Group A patients showed a significantly higher decrement in LV mass index (LVMI) than group B at the end of follow-up, after adjusting for age, baseline LVMI, time after grafting and changes in systolic blood pressure, renal function, and hemoglobin levels (group A, -9.5 +/- 3.5% vs. group B, 3 +/- 3.2%, P < 0.05). As a result, 46% of group A and only 7% of group B patients showed a reduction of LVMI >/=15% (P < 0.01). The beneficial effect of lisinopril on LVMI reduction was more evident in DD patients (placebo DD, 8.4 +/- 4.1% vs. lisinopril DD, -7.2 +/- 5.3, P < 0.05), and a trend was observed in patients with other genotypes (placebo ID/II, 2.8 +/- 5.4% vs. lisinopril ID/II, -11.4 +/- 5%, P = 0.33).

CONCLUSIONS

Lisinopril decreases LVM in renal transplant patients with hypertension and LVH, and the ACE gene polymorphism may predict the beneficial effect of this therapy. This finding may be important in targeting prophylactic interventions in this population.

Interleukin-7, a non-redundant potent cytokine whose over-expression massively perturbs B-lymphopoiesis

Interleukin-7, originally described as a factor controlling the survival of B-cell progenitors, has been shown by gene knock-out technology to be a non-redundant cytokine. Of all single cytokine knock-out mice, those in which the IL-7 gene has been ablated show a profound defect in lymphocyte development. Likewise, mice in which signals emanating from the corresponding receptor, whether it be by ablation of the unique alpha or common gamma chain of the receptor, or by interference with downstream signalling elements generated by this receptor complex, also show profound defects in lymphocyte differentiation. Transgenic mice over-expressing the IL-7 gene also show profound changes in lymphocyte development which, in some instances can result in the development of lymphoid tumours. Here, we review some of these aspects of IL-7 biology with particular reference to an IL-7 over-expressing transgenic mouse line in which the IL-7 transgene is controlled by the mouse MHC class II promoter.

Gastric mucosa abnormalities and tumorigenesis in mice lacking the pS2 trefoil protein

To determine the function of the pS2 trefoil protein, which is normally expressed in the gastric mucosa, the mouse pS2 (mpS2) gene was inactivated. The antral and pyloric gastric mucosa of mpS2-null mice was dysfunctional and exhibited severe hyperplasia and dysplasia. All homozygous mutant mice developed antropyloric adenoma, and 30 percent developed multifocal intraepithelial or intramucosal carcinomas. The small intestine was characterized by enlarged villi and an abnormal infiltrate of lymphoid cells. These results indicate that mpS2 is essential for normal differentiation of the antral and pyloric gastric mucosa and may function as a gastric-specific tumor suppressor gene.

Spread and maintenance of a dominant methicillin-resistant Staphylococcus aureus (MRSA) clone during an outbreak of MRSA disease in a Spanish hospital

It was not until November 1989 that the 1,000-bed University-affiliated Hospital de Bellvitge "Princeps d'Espanya" in Barcelona first acquired methicillin-resistant Staphylococcus aureus (MRSA). Since that time, the outbreak of MRSA disease has continued. We have analyzed by genomic DNA fingerprinting 189 MRSA isolates collected between late 1989 and the end of 1993. The isolates include both invasive and colonizing strains as well as isolates from health-care workers and environmental sources. In addition, 52 clinical isolates of methicillin-susceptible S. aureus (MSSA) collected in the same hospital were also analyzed. Isolates were classified into clonal types on the basis of molecular typing techniques. A single MRSA clone (I::B::a) belonging to ClaI type I, pulsed-field gel electrophoretic pattern B, and Tn554 pattern a was responsible for the great majority of infections (73% of blood cultures and 79% of specimens from other clinical sources). This clone appeared at the very beginning of the outbreak, spread throughout the hospital wards, and was also carried by inpatients and health-care workers and on environmental surfaces. In contrast, no dominant lineage was apparent among MSSA isolates (33 distinct pulsed-field gel electrophoretic patterns among 52 isolates). Two MSSA isolates seem to have originated from the dominant clone by deletion of the mecA gene and some additional DNA. In several isolates, different mecA polymorphs were present in identical chromosomal backgrounds or cells with distinct chromosomal backgrounds carried the same mecA polymorph, suggesting horizontal transfer of the mecA gene.

Myxoid change in decidualized scar endometriosis mimicking malignancy

A case of cesarean scar endometriosis with massive decidualization is presented. The 25-year-old patient had an extensive, ulcerated lesion that mimicked malignancy microscopically due to myxoid change with alveolar patterns reminiscent of some soft tissue sarcomas, signet ring-like cells similar to mucin-producing carcinoma, and pseudoinfiltration of the fascia. The myxoid tissue was positive for acid mucopolysaccharides but negative with PAS. Decidual cells were vimentin positive and keratin negative. No atypia or mitoses were seen. The pseudoinfiltrative aspect was due to abundant extracellular matrix that separated the fascicles of the fascial tissue. There was a metaplastic decidual "proximity effect" in the surrounding, unaffected dermis, which may be responsible for the expansile features of the lesion. This case exemplifies the differential diagnosis of myxoid endometriosis with malignant conditions of the skin.