Distinct profiles of proliferating CD8+/TCF1+ T cells and CD163+/PD-L1+ macrophages predict risk of relapse differently among treatment-naïve breast cancer subtypes.

Immunophenotypic analysis of breast cancer microenvironment is gaining attraction as a clinical tool improving breast cancer patient stratification. The aim of this study is to evaluate proliferating CD8 + including CD8 + TCF1 + Τ cells along with PD-L1 expressing tissue-associated macrophages among different breast cancer subtypes. A well-characterized cohort of 791 treatment-naïve breast cancer patients was included. The analysis demonstrated a distinct expression pattern among breast cancer subtypes characterized by increased CD8 + , CD163 + and CD163 + PD-L1 + cells along with high PD-L1 status and decreased fraction of CD8 + Ki67 + T cells in triple negative (TNBC) and HER2 + compared to luminal tumors. Kaplan-Meier and Cox univariate survival analysis revealed that breast cancer patients with high CD8 + , CD8 + Ki67 + , CD8 + TCF1 + cells, PD-L1 score and CD163 + PD-L1 + cells are likely to have a prolonged relapse free survival, while patients with high CD163 + cells have a worse prognosis. A differential impact of high CD8 + , CD8 + Ki67 + , CD8 + TCF1 + T cells, CD163 + PD-L1 + macrophages and PD-L1 status on prognosis was identified among the various breast cancer subtypes since only TNBC patients experience an improved prognosis compared to patients with luminal A tumors. Conversely, high infiltration by CD163 + cells is associated with worse prognosis only in patients with luminal A but not in TNBC tumors. Multivariate Cox regression analysis in TNBC patients revealed that increased CD8 + [hazard ratio (HR) = 0.542; 95% confidence interval (CI) 0.309-0.950; p = 0.032), CD8 + TCF1 + (HR = 0.280; 95% CI 0.101-0.779; p = 0.015), CD163 + PD-L1 + (HR: 0.312; 95% CI 0.112-0.870; p = 0.026) cells along with PD-L1 status employing two different scoring methods (HR: 0.362; 95% CI 0.162-0.812; p = 0.014 and HR: 0.395; 95% CI 0.176-0.884; p = 0.024) were independently linked with a lower relapse rate. Multivariate analysis in Luminal type A patients revealed that increased CD163 + was independently associated with a higher relapse rate (HR = 2.360; 95% CI 1.077-5.170; p = 0.032). This study demonstrates that the evaluation of the functional status of CD8 + T cells in combination with the analysis of immunosuppressive elements could provide clinically relevant information in different breast cancer subtypes.

Diagnostic Challenges during Inflammation and Cancer: Current Biomarkers and Future Perspectives in Navigating through the Minefield of Reactive versus Dysplastic and Cancerous Lesions in the Digestive System.

In the setting of pronounced inflammation, changes in the epithelium may overlap with neoplasia, often rendering it impossible to establish a diagnosis with certainty in daily clinical practice. Here, we discuss the underlying molecular mechanisms driving tissue response during persistent inflammatory signaling along with the potential association with cancer in the gastrointestinal tract, pancreas, extrahepatic bile ducts, and liver. We highlight the histopathological challenges encountered in the diagnosis of chronic inflammation in routine practice and pinpoint tissue-based biomarkers that could complement morphology to differentiate reactive from dysplastic or cancerous lesions. We refer to the advantages and limitations of existing biomarkers employing immunohistochemistry and point to promising new markers, including the generation of novel antibodies targeting mutant proteins, miRNAs, and array assays. Advancements in experimental models, including mouse and 3D models, have improved our understanding of tissue response. The integration of digital pathology along with artificial intelligence may also complement routine visual inspections. Navigating through tissue responses in various chronic inflammatory contexts will help us develop novel and reliable biomarkers that will improve diagnostic decisions and ultimately patient treatment.

An Unusual Manifestation of Brucella-Associated Uveitis in a Young Male Patient.

This is a unique case of retinoschisis as an ocular manifestation of brucellosis. A 38-year-old male presented with recurrent episodes of bilateral eye redness, predominately in his left eye. His visual acuity was not affected, and he did not report any other symptoms. On slit lamp examination, binocular Koeppe nodules of the iris and cells in the left anterior chamber were observed. Fundoscopy followed by meticulous multimodal imaging confirmed left inferior retinoschisis. The patient was diagnosed with panuveitis, and a series of laboratory examinations revealed positive anti-IgM Brucella antibodies. Ocular brucellosis can cause variable, atypical, and serious presentations, hence, early diagnosis is paramount to avoid complications.

Senescent cells in giant cell arteritis display an inflammatory phenotype participating in tissue injury via IL-6-dependent pathways.

OBJECTIVES: Age is the strongest risk factor of giant cell arteritis (GCA), implying a possible pathogenetic role of cellular senescence. To address this question, we applied an established senescence specific multimarker algorithm in temporal artery biopsies (TABs) of GCA patients. METHODS: 75(+) TABs from GCA patients, 22(-) TABs from polymyalgia rheumatica (PMR) patients and 10(-) TABs from non-GCA/non-PMR patients were retrospectively retrieved and analysed. Synovial tissue specimens from patients with inflammatory arthritis and aorta tissue were used as disease control samples. Senescent cells and their histological origin were identified with specific cellular markers; IL-6 and MMP-9 were investigated as components of the senescent associated secretory phenotype by triple costaining. GCA or PMR artery culture supernatants were applied to fibroblasts, HUVECs and monocytes with or without IL-6R blocking agent to explore the induction of IL-6-associated cellular senescence. RESULTS: Senescent cells were present in GCA arteries at higher proportion compared with PMR (9.50% vs 2.66%, respectively, p<0.0001) and were mainly originated from fibroblasts, macrophages and endothelial cells. IL-6 was expressed by senescent fibroblasts, and macrophages while MMP-9 by senescent fibroblasts only. IL-6(+) senescent cells were associated with the extension of vascular inflammation (transmural inflammation vs adventitia limited disease: 10.02% vs 4.37%, respectively, p<0.0001). GCA but not PMR artery culture supernatant could induce IL-6-associated senescence that was partially inhibited by IL-6R blockade. CONCLUSIONS: Senescent cells with inflammatory phenotype are present in GCA arteries and are associated with the tissue inflammatory bulk, suggesting a potential implication in disease pathogenesis.

Comprehensive Analysis of Virulence Determinants and Genomic Islands of blaNDM-1-Producing Enterobacter hormaechei Clinical Isolates from Greece.

Nosocomial outbreaks of multidrug-resistant (MDR) Enterobacter cloacae complex (ECC) are often reported worldwide, mostly associated with a small number of multilocus-sequence types of E. hormaechei and E. cloacae strains. In Europe, the largest clonal outbreak of blaNDM-1-producing ECC has been recently reported, involving an ST182 E. hormaechei strain in a Greek teaching hospital. In the current study, we aimed to further investigate the genetic make-up of two representative outbreak isolates. Comparative genomics of whole genome sequences (WGS) was performed, including whole genome-based taxonomic analysis and in silico prediction of virulence determinants of the bacterial cell surface, plasmids, antibiotic resistance genes and virulence factors present on genomic islands. The enterobacterial common antigen and the colanic antigen of the cell surface were identified in both isolates, being similar to the gene clusters of the E. hormaechei ATCC 49162 and E. cloacae ATCC 13047 type strains, whereas the two strains possessed different gene clusters encoding lipopolysaccharide O-antigens. Other virulence factors of the bacterial cell surface, such as flagella, fimbriae and pili, were also predicted to be encoded by gene clusters similar to those found in Enterobacter spp. and other Enterobacterales. Secretion systems and toxin-antitoxin systems, which also contribute to pathogenicity, were identified. Both isolates harboured resistance genes to multiple antimicrobial classes, including ß-lactams, aminoglycosides, quinolones, chloramphenicol, trimethoprim, sulfonamides and fosfomycin; they carried blaTEM-1, blaOXA-1, blaNDM-1, and one of them also carried blaCTXM-14, blaCTXM-15 and blaLAP-2 plasmidic alleles. Our comprehensive analysis of the WGS assemblies revealed that blaNDM-1-producing outbreak isolates possess components of the bacterial cell surface as well as genomic islands, harbouring resistance genes to several antimicrobial classes and various virulence factors. Differences in the plasmids carrying ß-lactamase genes between the two strains have also shown diverse modes of acquisition and an ongoing evolution of these mobile elements.

Acinetobacter baumannii Bloodstream Infections in the COVID-19 Era: A Comparative Analysis between COVID-19 and Non-COVID-19 Critically Ill Patients.

The coronavirus disease (COVID-19) pandemic increased the incidence of severe infections caused by multidrug-resistant (MDR) pathogens among critically ill patients, such as Acinetobacter baumannii (AB), whose bloodstream infections (BSIs) have been associated with significant mortality. Whether there is any difference in outcome between COVID-19 and non-COVID-19 patients with AB BSI still remains unknown. We conducted a retrospective study comparing clinical characteristics and outcomes of COVID-19 versus non-COVID-19 critically ill patients with AB BSI. Overall, 133 patients with AB BSI (102 COVID-19, 31 non-COVID-19) were studied. The 28-day mortality rate was high and did not differ significantly (69.6% COVID-19 vs. 61.3% non-COVID-19, p = 0.275). Patients with septic shock had a higher mortality rate irrespective of their status with the majority of deaths occurring during the first 7 days. COVID-19 patients were more likely to have ventilator-associated pneumonia (VAP) as the source of BSI (55.8% vs. 22.3%, respectively, p = 0.0001) and were more likely to develop acute respiratory distress syndrome (ARDS) (78.4% vs. 48.4%, respectively, p = 0.001), sepsis (86.3% vs. 67.7%, respectively, p = 0.03), and septic shock (88.3% vs. 58.1%, respectively, p = 0.007) compared to the non-COVID-19 patient group. In conclusion, COVID-19 patients with A. baumannii BSI have a high rate of mortality and more often develop septic shock, while VAP is the main origin of their BSI.

Recurrent Scedosporium apiospermum Cutaneous Infection in a Patient with Rheumatoid Arthritis: The Potent Role of IL-6 Signaling Pathway Blockade: A Case-Based Review.

Rheumatoid arthritis (RA) patients deal with a higher risk of bacterial and fungal infections compared to the general population because of their dysregulated immune system as well as the immunosuppressive therapy they usually receive. Scedosporium spp. is a fungal pathogen responsible for cutaneous, lung, central nervous system, and eye infections, mostly in immunocompromised patients, leading to death in disseminated cases. We report the case of an 81-year-old woman with rheumatoid arthritis treated with steroids and an IL-6 inhibitor who was diagnosed with scedosporiosis of the upper limb. She was treated with voriconazole for one month, which was discontinued due to adverse events, and when scedosporiosis relapsed, she switched to itraconazole. We also reviewed the current literature on RA patients presenting with Scedosporium infections. Early and accurate diagnosis of scedosporiosis has therapeutic and prognostic implications, as traditionally this fungus is resistant to commonly used antifungals. Clinical alertness regarding uncommon infections, including fungal, in patients with autoimmune diseases on immunomodulatory agents is essential for effective treatment.

Fibroadenoma Arising in Axillary Ectopic Breast Tissue. A Diagnostic Challenge.

Ectopic or accessory breast tissue may occur in primitive embryonic milk lines or locations other than the milk line. The same pathology arising in breast tissue may occur less frequently in ectopic breast tissue. Fibroadenomas rarely occur in ectopic breast tissue, with less than 50 reported cases in the English literature, despite being the most common benign breast neoplasms. Diagnosing fibroadenoma in ectopic breast tissue can be challenging due to the lack of clinical suspicion and the atypical findings in imaging studies. Treatment consists of surgical excision. In this manuscript, we present a case of a 24-year-old patient with a fibroadenoma of the left axilla arising in bilateral axillary ectopic breast tissue, and we comprehensively review the literature.

Significance of MYB and NTRK Expression in Head and Neck Adenoid Cystic Carcinoma.

BACKGROUND/AIM: Adenoid cystic carcinoma (ACC) is an aggressive neoplasm even though it has low-grade histological appearance and slow growth. The aim of this study was to identify the immunohistochemical and molecular characteristics of ACC, as well as their correlation with the clinical course of patients. PATIENTS AND METHODS: This is a retrospective multicenter analysis. We included 50 patients diagnosed with ACC in the head and neck between 2000 and 2021. The expression of MYB proto-oncogene transcription factor (MYB), neurotrophic tyrosine kinase receptor (NTRK), human epidermal receptor-2 (HER-2), and Ki-67 was examined through immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). We also performed a clinical follow-up of the patients. RESULTS: The median age of the patients was 58.5 years; moreover, 54% of the patients were male. Compared with female patients, male patients were at a higher risk of both recurrence and death. No HER-2-positive cases were revealed. MYB expression was positive in 28 (56%) cases. However, MYB expression did not significantly affect survival. NTRK expression was positive in eight (16%) cases. NTRK-positive patients had worse overall survival (OS) than NTRK-negative patients (p=0.0246). Additionally, the percentage of NTRK-stained cells was negatively correlated with disease-free survival (p=0.0016) and OS (p=0.0027). CONCLUSION: There was no correlation between MYB positivity and survival. Contrarily, NTRK-positive patients had worse survival, indicating that NTRK is a negative prognostic factor. Tropomyosin receptor kinase inhibitors can be used to treat these patients. Furthermore, MYB-targeted inhibitors are promising therapeutic agents.

Pulmonary infection by SARS-CoV-2 induces senescence accompanied by an inflammatory phenotype in severe COVID-19: possible implications for viral mutagenesis.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection of the respiratory system can progress to a multisystemic disease with aberrant inflammatory response. Cellular senescence promotes chronic inflammation, named senescence-associated secretory phenotype (SASP). We investigated whether coronavirus disease 2019 (COVID-19) is associated with cellular senescence and SASP. METHODS: Autopsy lung tissue samples from 11 COVID-19 patients and 43 age-matched non-COVID-19 controls with similar comorbidities were analysed by immunohistochemistry for SARS-CoV-2, markers of senescence and key SASP cytokines. Virally induced senescence was functionally recapitulated in vitro, by infecting epithelial Vero-E6 cells and a three-dimensional alveosphere system of alveolar type 2 (AT2) cells with SARS-CoV-2 strains isolated from COVID-19 patients. RESULTS: SARS-CoV-2 was detected by immunocytochemistry and electron microscopy predominantly in AT2 cells. Infected AT2 cells expressed angiotensin-converting enzyme 2 and exhibited increased senescence (p16INK4A and SenTraGor positivity) and interleukin (IL)-1ß and IL-6 expression. In vitro, infection of Vero-E6 cells with SARS-CoV-2 induced senescence (SenTraGor), DNA damage (γ-H2AX) and increased cytokine (IL-1ß, IL-6, CXCL8) and apolipoprotein B mRNA-editing (APOBEC) enzyme expression. Next-generation sequencing analysis of progenies obtained from infected/senescent Vero-E6 cells demonstrated APOBEC-mediated SARS-CoV-2 mutations. Dissemination of the SARS-CoV-2-infection and senescence was confirmed in extrapulmonary sites (kidney and liver) of a COVID-19 patient. CONCLUSIONS: We demonstrate that in severe COVID-19, AT2 cells infected by SARS-CoV-2 exhibit senescence and a proinflammatory phenotype. In vitro, SARS-CoV-2 infection induces senescence and inflammation. Importantly, infected senescent cells may act as a source of SARS-CoV-2 mutagenesis mediated by APOBEC enzymes. Therefore, SARS-CoV-2-induced senescence may be an important molecular mechanism of severe COVID-19, disease persistence and mutagenesis.

SARS-CoV-2 Antigenemia as a Confounding Factor in Immunodiagnostic Assays: A Case Study.

Humoral immunity has emerged as a vital immune component against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Nevertheless, a subset of recovered Coronavirus Disease-2019 (COVID-19) paucisymptomatic/asymptomatic individuals do not generate an antibody response, constituting a paradox. We assumed that immunodiagnostic assays may operate under a competitive format within the context of antigenemia, potentially explaining this phenomenon. We present a case where persistent antigenemia/viremia was documented for at least 73 days post-symptom onset using 'in-house' methodology, and as it progressively declined, seroconversion took place late, around day 55, supporting our hypothesis. Thus, prolonged SARS-CoV-2 antigenemia/viremia could mask humoral responses, rendering, in certain cases, the phenomenon of 'non-responders' a misnomer.

A Paraganglioma in the Right Supraclavicular Fossa: Mistaken for a Thyroid Mass.

Paragangliomas are rare lesions of the endocrine system that can be treated either by embolization preoperatively followed by surgical excision or by surgical excision or radiotherapy. In this report, we present an extremely rare location of a nonfunctional paraganglioma in the head and neck region, located in the right supraclavicular fossa, which was misdiagnosed as a thyroid tumor, in a 72-year-old female patient. Imaging revealed a 2.5 × 4.5 × 2 cm well-defined vascularized mass. Fine-needle aspiration (FNA) on the tumor was not diagnostic initially; however, a third attempt revealed thyroid cells suggesting the existence of an ectopic thyroid tumor. FNA was additionally performed on the right thyroid lobe, revealing atypical follicular colloid cells of the Bethesda 3 category. Therefore, the excision of the ectopic thyroid tumor along with right lobectomy was planned. No embolization was initiated preoperatively in this case. Histopathology revealed that the supraclavicular mass was a paraganglioma. Paragangliomas supplied by the subclavian, innominate, and common carotid artery are rarely reported, and to our knowledge, this is the third case to be reported worldwide.

Onychomycosis in Northwestern Greece Over a 7-Year Period.

Onychomycosis is considered as one of the major public health problems with a global distribution associated with geographic, demographic and environmental factors, underlying comorbidities and immunodeficiency disorders. This study was conducted to investigate the etiological agents of onychomycosis, in Northwestern Greece during a 7-year period. The study population included 1095 outpatients with clinically suspected onychomycosis that presented to the University Hospital of Ioannina, NW Greece (2011-2017). Samples were examined for causative fungi, and mycological identification was established using standard mycological methods. Demographic data of each patient, comorbidities, localization of infection and history of previous fungal infection were collected. Onychomycosis was diagnosed in 317 of the 1095 suspected cases (28.9%) and the most frequently isolated pathogens were yeasts (50.8%) followed by dermatophytes (36.9%) and non-dermatophyte molds (NDMs) (12.3%). Dermatophytes were mostly involved in toenail onychomycosis (90.6%) and more commonly affected males than females (57.3% vs. 42.7%), while the predominantly isolated pathogen was Τrichophyton rubrum (74.4%) followed by Τrichophyton interdigitale (21.4%). Candida albicans was the most prevalent isolated yeast (82%), whereas among the cases with onychomycosis due to NDMs, Aspergillus spp. were isolated as the principal species (59%). Continuous monitoring should be performed in order to identify possible trends and shifts in species isolation rates and to evaluate the impact of onychomycosis among the general population and high-risk groups.

Unique Spatial Immune Profiling in Pancreatic Ductal Adenocarcinoma with Enrichment of Exhausted and Senescent T Cells and Diffused CD47-SIRPα Expression.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is resistant to single-agent immunotherapies. To understand the mechanisms leading to the poor response to this treatment, a better understanding of the PDAC immune landscape is required. The present work aims to study the immune profile in PDAC in relationship to spatial heterogeneity of the tissue microenvironment (TME) in intact tissues. METHODS: Serial section and multiplex in situ analysis were performed in 42 PDAC samples to assess gene and protein expression at single-cell resolution in the: (a) tumor center (TC), (b) invasive front (IF), (c) normal parenchyma adjacent to the tumor, and (d) tumor positive and negative draining lymph nodes (LNs). RESULTS: We observed: (a) enrichment of T cell subpopulations with exhausted and senescent phenotype in the TC, IF and tumor positive LNs; (b) a dominant type 2 immune response in the TME, which is more pronounced in the TC; (c) an emerging role of CD47-SIRPα axis; and (d) a similar immune cell topography independently of the neoadjuvant chemotherapy. CONCLUSION: This study reveals the existence of dysfunctional T lymphocytes with specific spatial distribution, thus opening a new dimension both conceptually and mechanistically in tumor-stroma interaction in PDAC with potential impact on the efficacy of immune-regulatory therapeutic modalities.

Senescence and senotherapeutics: a new field in cancer therapy.

Cellular senescence is a stress response mechanism ensuring homeostasis. Its temporal activation during embryonic development or normal adult life is linked with beneficial properties. In contrast, persistent (chronic) senescence seems to exert detrimental effects fostering aging and age-related disorders, such as cancer. Due to the lack of a reliable marker able to detect senescence in vivo, its precise impact in age-related diseases is to a large extent still undetermined. A novel reagent termed GL13 (SenTraGorTM) that we developed, allowing senescence recognition in any type of biological material, emerges as a powerful tool to study the phenomenon of senescence in vivo. Exploiting the advantages of this novel methodological approach, scientists will be able to detect and connect senescence with aggressive behavior in human malignancies, such as tolerance to chemotherapy in classical Hodgkin Lymphoma and Langerhans Cell Histiocytosis. The latter depicts the importance of developing the new and rapidly expanding field of senotherapeutic agents targeting and driving to cell death senescent cells. We discuss in detail the current progress of this exciting area of senotherapeutics and suggest its future perspectives and applications.

Age-related EBV positive clonal B-cell Lymphoid proliferation (EBV+-DLBCL).

The Ebstein Barr virus(EBV), herpes virus 5 has been associated with lymphoproliferative disordrers. Age-related EBV+ B-LPD is defined as an EBV+ clonal B-cell lymphoid proliferation or EBV+-DLBCL developing in patients over the age of 40 years in the absence of any known immunodeficiency and without an underlying T-cell lymphoma1. We present a case of EBV+ clonal B-cell lymphoid proliferation. Key words:Oral mucosa ulcer, EBV+-DLBCL, age related.

Oral non-Hodgkin's lymphoma in a patient with rheumatoid arthritis treated with etanercept and methotrexate.

Oral non-Hodgkin's lymphomas (O-NHLs) are a rare group of diverse lymphoid tissue malignancies and represent less than 5% of the oral cavity malignancies and 2% of all extra-nodal NHLs. Oral-NHLs affect the Waldeyer's-ring, the salivary glands, the bone of the jaws and the oral mucosa, their clinical appearance is very heterogeneous. Among the risk factors for NHLs are immunosuppression (primary or secondary), autoimmunity and inflammation. O-NHLs share the same risk factors. This case report describes a patient with O-NHL which was possibly linked to the combination of methotrexate and etanercept for the treatment of her rheumatoid arthritis. To our knowledge this is probably among the first cases of O-NHL with possible relation to the use of a Tumor Necrosis Factor (TNF) antagonist biological agent (etanercept). This case could contribute to the sensitization of the dentists for the signs and symptoms of this rare malignancy. It also underlines the need for thorough medical history and medication recording for all the dental patients. Key words:Lymphoma (oral) methotrexate, etanercept.

Functional p53 can modulate the relationship between E2F-1 expression and tumor kinetics in Hodgkin lymphoma.

E2F-1 is the best-described member of the E2F family of transcriptional factors and is particularly interesting in view of its often opposing roles. Our purpose was to examine the immunohistochemical expression of E2F-1 in Hodgkin lymphoma (HL) and to correlate it with proliferation and apoptosis of the tumor, clinicopathological parameters and patient outcome, as well as with expression of the downstream molecules p53 and p21. The median percentage of E2F-1-expressing Hodgkin Reed-Sternberg (HRS) cells was 80.2%. A significant positive correlation was found between expression of E2F-1 and p53 (p = 0.034). Following stratification of our cases, within the group harboring functional p53, a statistically significant inverse correlation was identified between E2F-1 and Topo IIa (p = 0.019). E2F-1 is up-regulated in the context of HL and its expression is inversely associated with proliferation. It seems that functional p53 can modulate the relationship between E2F-1 expression and tumor kinetics in HL.

The relationship between E2F family members and tumor growth in colorectal adenocarcinomas: A comparative immunohistochemical study of 100 cases.

The mammalian E2F family of transcription factors comprises a group of 8 proteins, which either activate or repress transcription of numerous target genes, playing a role in cell-cycle progression and apoptosis. We have collectively investigated the immunohistochemical expression of E2F1, E2F2, and E2F4 transcription factors and their relation to cell kinetic parameters using serial section analysis in a series of 100 cases of human colorectal adenocarcinomas. E2F1 and E2F4 expressed nuclear immunopositivity in all cases. The range of their expression was 2% to 80% (mean 21% ± 15%) and 2% to 90% (mean 66% ± 20%), respectively. E2F2 was expressed in 41 cases at low levels (range, 1% to 5%, mean 2% ± 9%). A statistically significant direct association between E2F4 and cell proliferation, as expressed by high levels of Ki-67 labeling index, was shown. A mutually exclusive immunostaining pattern between E2F1 and E2F4 and a direct correlation of E2F1 and apoptosis were also highlighted. Our results point to a possible direct tumor-promoting role for E2F4 in the context of colorectal carcinogenesis. The inverse immunohistochemical relationship between E2F1 and E2F4 indicates a possible mechanistic interlink in colorectal cancer. Low expression of E2F2 may reflect functional redundancy between members of the E2F family, in this case between E2F1 and E2F2.