PTP-PEST controls EphA3 activation and ephrin-induced cytoskeletal remodelling.

Eph receptors and their corresponding membrane-bound ephrin ligands regulate cell positioning and establish tissue patterns during embryonic and oncogenic development. Emerging evidence suggests that assembly of polymeric Eph signalling clusters relies on cytoskeletal reorganisation and underlies regulation by protein tyrosine phosphatases (PTPs). PTP-PEST (also known as PTPN12) is a central regulator of actin cytoskeletal dynamics. Here, we demonstrate that an N-terminal fragment of PTP-PEST, generated through an ephrinA5-triggered and spatially confined cleavage mediated by caspase-3, attenuates EphA3 receptor activation and its internalisation. Isolation of EphA3 receptor signalling clusters within intact plasma membrane fragments obtained by detergent-free cell fractionation reveals that stimulation of cells with ephrin triggers effective recruitment of this catalytically active truncated form of PTP-PEST together with key cytoskeletal and focal adhesion proteins. Importantly, modulation of actin polymerisation using pharmacological and dominant-negative approaches affects EphA3 phosphorylation in a similar manner to overexpression of PTP-PEST. We conclude that PTP-PEST regulates EphA3 activation both by affecting cytoskeletal remodelling and through its direct action as a PTP controlling EphA3 phosphorylation, indicating its multifaceted regulation of Eph signalling.

Correction: The Subclonal Architecture of Metastatic Breast Cancer: Results from a Prospective Community-Based Rapid Autopsy Program "CASCADE".

[This corrects the article DOI: 10.1371/journal.pmed.1002204.].

Advancing Immunotherapy in Metastatic Breast Cancer.

OPINION STATEMENT: Despite many advances in the treatment of breast cancer, the development of metastatic disease remains an incurable and frequent cause of cancer death for women worldwide. An improved understanding of the role of host immunosurveillance in modulating breast cancer disease biology, as well as impressive survival benefits seen to checkpoint blockade in other malignancies have provided great hope for an expanding role of immunotherapies in breast cancer management. While these novel therapies are currently being investigated in clinical trials, signals of efficacy, and tolerability in early phase studies suggest these will eventually make their way into standard practice algorithms. Ongoing research has highlighted a high degree of intertumoural heterogeneity in tumour lymphocytic infiltrates, suggesting some tumours or subtypes are more immunogenic than others. Furthermore, tumour intrinsic mechanisms of immune evasion are beginning to be uncovered, potentially representing key therapeutic targets to use in combination with checkpoint blockade, exemplifying the emerging concept of personalised medicine approaches to immune therapies. Subsequently, different immunotherapeutic strategies may be required based on stratification by these factors-for the minority of tumours with a high level of pre-existing immunity, immune checkpoint blockade monotherapy may be sufficient. However, for the majority of tumours with lower levels of pre-existing immunity, combination approaches will likely be required to achieve maximal therapeutic effect. Results of ongoing clinical trials including combinations with chemotherapy, radiation therapy, and targeted therapies are eagerly awaited.

Visual and Motor Recovery After "Cognitive Therapeutic Exercises" in Cortical Blindness: A Case Study.

BACKGROUND AND PURPOSE: Spontaneous visual recovery is rare after cortical blindness. While visual rehabilitation may improve performance, no visual therapy has been widely adopted, as clinical outcomes are variable and rarely translate into improvements in activities of daily living (ADLs). We explored the potential value of a novel rehabilitation approach "cognitive therapeutic exercises" for cortical blindness. CASE DESCRIPTION: The subject of this case study was 48-year-old woman with cortical blindness and tetraplegia after cardiac arrest. Prior to the intervention, she was dependent in ADLs and poorly distinguished shapes and colors after 19 months of standard visual and motor rehabilitation. Computed tomographic images soon after symptom onset demonstrated acute infarcts in both occipital cortices. INTERVENTION: The subject underwent 8 months of intensive rehabilitation with "cognitive therapeutic exercises" consisting of discrimination exercises correlating sensory and visual information. OUTCOMES: Visual fields increased; object recognition improved; it became possible to watch television; voluntary arm movements improved in accuracy and smoothness; walking improved; and ADL independence and self-reliance increased. Subtraction of neuroimaging acquired before and after rehabilitation showed that focal glucose metabolism increases bilaterally in the occipital poles. DISCUSSION: This study demonstrates feasibility of "cognitive therapeutic exercises" in an individual with cortical blindness, who experienced impressive visual and sensorimotor recovery, with marked ADL improvement, more than 2 years after ischemic cortical damage.Video Abstract available for additional insights from the authors (see Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A173).

The Subclonal Architecture of Metastatic Breast Cancer: Results from a Prospective Community-Based Rapid Autopsy Program "CASCADE".

BACKGROUND: Understanding the cancer genome is seen as a key step in improving outcomes for cancer patients. Genomic assays are emerging as a possible avenue to personalised medicine in breast cancer. However, evolution of the cancer genome during the natural history of breast cancer is largely unknown, as is the profile of disease at death. We sought to study in detail these aspects of advanced breast cancers that have resulted in lethal disease. METHODS AND FINDINGS: Three patients with oestrogen-receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer and one patient with triple negative breast cancer underwent rapid autopsy as part of an institutional prospective community-based rapid autopsy program (CASCADE). Cases represented a range of management problems in breast cancer, including late relapse after early stage disease, de novo metastatic disease, discordant disease response, and disease refractory to treatment. Between 5 and 12 metastatic sites were collected at autopsy together with available primary tumours and longitudinal metastatic biopsies taken during life. Samples underwent paired tumour-normal whole exome sequencing and single nucleotide polymorphism (SNP) arrays. Subclonal architectures were inferred by jointly analysing all samples from each patient. Mutations were validated using high depth amplicon sequencing. Between cases, there were significant differences in mutational burden, driver mutations, mutational processes, and copy number variation. Within each case, we found dramatic heterogeneity in subclonal structure from primary to metastatic disease and between metastatic sites, such that no single lesion captured the breadth of disease. Metastatic cross-seeding was found in each case, and treatment drove subclonal diversification. Subclones displayed parallel evolution of treatment resistance in some cases and apparent augmentation of key oncogenic drivers as an alternative resistance mechanism. We also observed the role of mutational processes in subclonal evolution. Limitations of this study include the potential for bias introduced by joint analysis of formalin-fixed archival specimens with fresh specimens and the difficulties in resolving subclones with whole exome sequencing. Other alterations that could define subclones such as structural variants or epigenetic modifications were not assessed. CONCLUSIONS: This study highlights various mechanisms that shape the genome of metastatic breast cancer and the value of studying advanced disease in detail. Treatment drives significant genomic heterogeneity in breast cancers which has implications for disease monitoring and treatment selection in the personalised medicine paradigm.

Relevance of tumor-infiltrating lymphocytes in breast cancer.

While breast cancer has not been considered a cancer amenable to immunotherapeutic approaches, recent studies have demonstrated evidence of significant immune cell infiltration via tumor-infiltrating lymphocytes in a subset of patient tumors. In this review we present the current evidence highlighting the clinical relevance and utility of tumor-infiltrating lymphocytes in breast cancer. Retrospective and prospective studies have shown that the presence of tumor-infiltrating lymphocytes is a prognostic marker for higher responses to neoadjuvant chemotherapy and better survival, particularly in triple negative and HER2-positive early breast cancer. Further work is required to determine the immune subsets important in this response and to discover ways of encouraging immune infiltrate in tumor-infiltrating lymphocytes-negative patients.

Magnetic resonance imaging of the cerebellopontine angle: comparison between constructive interference steady-state and small field-of-view technique turbo spin echo sequences.

BACKGROUND: The aim of this work was to optimize a three-dimensional (3D) turbo-spin-echo (TSE) sequence using a small field-of-view (FOV) technique for the study of the cerebellopontine angle and to compare it with a constructive interference steady-state (CISS) sequence. METHODS: A total of 30 consecutive patients underwent magnetic resonance imaging with a 3Tesla (T) scanner, including 3D CISS and the optimized 3D small FOV technique turbo spin echo (3D SFT-TSE) T2-weighted sequences for the study of the cerebellopontine angle. The 3D SFT-TSE sequence was optimized after three different steps, and a quantitative evaluation of the signal-to-noise ratio (SNR) was obtained according to the National Electrical Manufacturers Association (NEMA) method. Three neuroradiologists made a blind comparative qualitative evaluation of the images between the 3D CISS and the 3D SFT-TSE obtained after the third optimization step, based on spatial resolution, contrast resolution, and presence of artifacts and noise. RESULTS: The calculation of SNR using the NEMA method confirmed the superiority of the third optimization step over the others. For both spatial and contrast resolution, the optimized SFT-TSE was considered better (p < 0.001) than the CISS, while image artifacts and noise were considered worse in the CISS sequence (p < 0.001). Intraobserver analysis showed that all neuroradiologists preferred the 3D SFT-TSE sequence in terms of both spatial resolution and contrast resolution and found more noise and artifact disruption in the CISS sequence. CONCLUSIONS: The use of the 2D radiofrequency pulse technique with a 3D SFT-TSE T2 sequence was significantly more efficient than the 3D CISS sequence for the study of the cerebellopontine angle and inner ear structures.

Association of Elevated C-Reactive Protein with Worsened Outcomes in Different Histologies of Renal Cortical Tumors: Analysis of the INMARC Registry.

BACKGROUND: To evaluate relationship between histological subtypes of renal cell carcinoma (RCC) and preoperative c-reactive protein (CRP). PATIENTS AND METHODS: We queried the International Marker Consortium for Renal Cancer database for patients affected by RCC. Patients were classified according to their histology: benign tumors, clear cell (cc) RCC, chromophobe (ch) RCC, papillary (p) RCC, and variant histology (vh) RCC; and according to CRP (mg/L): low CRP ≤5 and high CRP >5. Primary outcome was all-cause mortality (ACM). Secondary outcomes were cancer-specific mortality (CSM), recurrence and association between CRP and histology. Multivariable analysis (MVA) via Cox regression and multivariable logistic regression were fitted to elucidate predictors of outcomes. RESULTS: Total 3902 patients (high CRP n = 1266) were analyzed; median follow up 51 (IQR 20-91) months. On MVA elevated CRP was an independent risk factor associated with increased risk of ACM in benign tumors (HR 5.98, P < .001), ccRCC (HR 2.69, P < .001), chRCC (HR 3.99, P < .001), pRCC (HR 1.76, P = .009) and vhRCC (HR 2.97, P =.007). MVA for CSM showed CRP as risk factor in ccRCC (HR 2.77, P < .001), chRCC (HR 6.16, P = .003) and pRCC (HR 2.29, P = .011), while in vhRCC was not (P = .27). MVA for recurrence reported CRP as risk factor for ccRCC (HR 1.30, P = .013), while in chRCC (P = .33), pRCC (P = .34) and vhRCC (P = .52) was not. On multivariable logistic regression CRP was a predictor of pRCC (OR 1.003, P = .002), while decreasing CRP was associated with benign tumors (OR 0.994, P = .048). CONCLUSION: Elevated CRP was a robust predictor of worsened ACM in all renal cortical neoplasms. While most frequently observed in pRCC patients, elevated CRP was independently associated with worsened CSM in non-vhRCC. Conversely, elevated CRP was least likely to be noted in benign tumors, and elevation in this subgroup of patients should prompt further consideration for surveillance given increased risk of ACM. Further investigation is requisite.

Combined Charlson comorbidity/C-Reactive Protein Index Is a Novel Predictor in Renal Cell Carcinoma: Analysis of the International Marker Consortium for Renal Cancer (INMARC) Registry.

OBJECTIVE: To evaluate predictive ability of a novel combined index, Charlson comorbidity index and C-reactive protein (CCI-CRP), for outcomes in renal cell carcinoma (RCC), and compare predictive outcomes with of CCI-CRP to its separate components and to the UCLA integrated staging system (UISS). PATIENTS AND METHODS: We retrospectively analyzed INMARC registry of RCC patients. Receiver Operator Characteristics (ROC) analysis was fitted to identify threshold defining low-CRP (LCRP) and high-CRP (HCRP). Patients were stratified according to CCI [low-CCI ≤ 3 (LCCI); intermediate-CCI 4-6 (ICCI); high-CCI > 6 (HCCI)] and CRP level. Kaplan-Meier analysis (KMA) was conducted for overall (OS) and cancer-specific survival (CSS). Based on survival analysis distribution we proposed a new stratification: CCI-CRP. Model performance was assessed with ROC/area under the curve (AUC) analysis and compared to CCI and CRP alone, and UISS. RESULTS: We analyzed 2,890 patients (median follow-up 30 months). ROC identified maximum product sensitivity and specificity for CRP at 3.5 mg/L. KMA revealed 5-year OS of 95.6% for LCRP/LCCI, 83% LCRP/ICCI, 73.3% LCRP/HCCI, 62.6% HCRP/LCCI, 51.6% HCRP/ICCI and 40.5% HCRP/HCCI (P < .001). From this distribution, new CCI-CRP is proposed: low CCI-CRP (LCRP/LCCI and LCRP/ICCI), intermediate CCI-CRP (LCRP/HCCI and HCRP/LCCI), and high CCI-CRP (HCRP/ICCI and HCRP/HCCI). AUC for CCI-CRP showed improved performance for predicting OS/CSS vs. CCI alone (0.73 vs. 0.63/0.77 vs. 0.60), CRP alone (0.73 vs. 0.71/0.77 vs. 0.74) and UISS (0.73 vs 0.67/0.77 vs 0.73). CONCLUSIONS: CCI-CRP, exhibits increased prognostic performance for survival outcomes in RCC compared to CCI and CRP alone, and UISS. Further investigation is requisite.

The Molecular Mechanisms of Complement Receptor 1-It Is Complicated.

Human complement receptor 1 (CR1) is a membrane-bound regulator of complement that has been the subject of recent attempts to generate soluble therapeutic compounds comprising different fragments of its extracellular domain. This review will focus on the extracellular domain of CR1 and detail how its highly duplicated domains work both separately and together to mediate binding to its main ligands C3b and C4b, and to inhibit the classical, lectin, and alternative pathways of the complement cascade via the mechanisms of decay acceleration activity (DAA) and co-factor activity (CFA). Understanding the molecular basis of CR1 activity is made more complicated by the presence not only of multiple ligand binding domains within CR1 but also the fact that C3b and C4b can interact with CR1 as both monomers, dimers, and heterodimers. Evidence for the interaction of CR1 with additional ligands such as C1q will also be reviewed. Finally, we will bring the mechanistic understanding of CR1 activity together to provide an explanation for the differential complement pathway inhibition recently observed with CSL040, a soluble CR1-based therapeutic candidate in pre-clinical development.

Modification of MRI pattern of high-grade glioma pseudoprogression in regorafenib therapy.

Pseudoprogression (PP) is a diagnostic dilemma in the follow-up of brain high grade gliomas (HGG), and the introduction of new therapies has further complicated its identification in Magnetic Resonance Imaging (MRI). We report a case of pseudoprogression after intraoperative radiotherapy (ioRT) and Regorafenib therapy in a patient with anaplastic astrocytoma recurrence. A 65-year-old man, treated in August 2017 for a right frontal anaplastic astrocytoma, with surgical resection and following radiotherapy and Temozolomide, in October 2019 was again treated for peri-surgical bed recurrence with resection and ioRT followed by Regorafenib therapy, interrupted in February 2020, after the onset of adverse reactions. MRI examination showed a large irregular alteration posterior to the surgical bed, T2 weighted hypointense featuring strong diffusion restriction (low ADC values), with an irregular contrast-enhancement (CE) pattern, and surrounded by a vast vasogenic oedema; Dynamic Susceptibility Contrast (DSC) perfusion imaging (PWI) showed no increase of relative cerebral blood volume (rCBV). Particularly, lesion appeared markedly hypointense and dusty-like on susceptibility weighted images (SWI) probably due to a constant hemorrhagic diapedesis promoted by Regorafenib. Therefore, pseudoprogression was suspected. Follow-up MRI exams showed gradual reduction of SWI and CE abnormalities, but a persistent DWI restriction. Unfortunately, the last MRI control showed a secondary cerebellar localisation of the disease. New therapies are changing MRI pattern in HGG imaging and this case underlines how a multimodality approach is increasingly necessary. In particular, when using anti-VEGF drugs, SWI can have a crucial role in identifying therapy-related haemorrhagic changes.

Non-traumatic Myositis Ossificans as Unusual Cause of Neck Pain During COVID-19 Pandemic: a Case Report.

Myositis ossificans circumscripta (MOC) is a benign disease characterized by localized heterotopic bone formation within muscles or soft tissue, usually interesting great muscles of extremities. We report a rare case of unusual location in the neck not associated with previous trauma, mimicking a solid tumor, with well-documented diagnostic imaging features. During COVID-19 pandemic outbreak in Italy, in May 2020, a 14-year-old boy developed a progressive and persistent neck pain on the right side, without known history of trauma. Initial therapy with non-steroid anti-inflammatory drugs and physiokinetic therapy gave only a slight improvement. A neck ultrasound showed an inhomogeneous right neck mass, with posterior shadowing due to calcifications. Computed tomography and magnetic resonance imaging confirmed a huge right neck mass, located in the paravertebral space with peripheral calcifications and mild central contrast enhancement. After surgical excision of the lesion, pathology revealed the presence of muscular tissue mixed with fibroblastic/myofibroblastic proliferation and ossification areas consistent with myositis ossificans. A careful analysis of clinical and radiological features is very important to manage young patients showing progressive pain and swelling of the neck, since MOC can mimic soft tissue or bone tumors, and it should be suspected even in the absence of a known history of trauma.

Elevated protein tyrosine phosphatase activity provokes Eph/ephrin-facilitated adhesion of pre-B leukemia cells.

Signaling by Eph receptors and cell-surface ephrin ligands modulates adhesive cell properties and thereby coordinates cell movement and positioning in normal and oncogenic development. While cell contact-dependent Eph activation frequently leads to cell-cell repulsion, also the diametrically opposite response, cell-cell adhesion, is a probable outcome. However, the molecular principles regulating such disparate functions have remained controversial. We have examined cell-biologic mechanisms underlying this switch by analyzing ephrin-A5-induced cell-morphologic changes of EphA3-positive LK63 pre-B acute lymphoblastic leukemia cells. Their exposure to ephrin-A5 surfaces leads to a rapid conversion from a suspended/nonpolarized to an adherent/polarized cell type, a transition that relies on EphA3 functions operating in the absence of Eph-kinase signaling. Cell morphology change and adhesion of LK63 cells are effectively attenuated by endogenous protein tyrosine phosphatase (PTP) activity, whereby PTP inhibition and productive EphA3-phosphotyrosine signaling reverse the phenotype to nonadherent cells with a condensed cytoskeleton. Our findings suggest that Eph-associated PTP activities not only control receptor phosphorylation levels, but as a result switch the response to ephrin contact from repulsion to adhesion, which may play a role in the pathology of hematopoietic tumors.

Spinal 'flip-flop' effect in anorexia nervosa: A case report.

Anorexia nervosa is a psychiatric eating disorder related to malnutrition and consequent altered metabolism. A 48-year-old female with a history of anorexia in the last 2 years referred to our hospital with spinal pain. She underwent spinal X-ray and magnetic resonance imaging (MRI) showing multiple vertebral collapses in dorsal and lumbar spine with inversion of normal bone marrow and soft tissue signal in T1-weighted and STIR images. We describe this case of spinal 'flip-flop' phenomenon, underlining how what seems a technical failure is actually a specific imaging pattern related to the clinical context.

Human papillomavirus type 77 E7 protein is a weak deregulator of cell cycle.

Human Papillomavirus type 77 is a skin type found in non-melanoma skin cancers of immuno-compromised individuals. Although, the HPV77 E6 oncoprotein has been well studied, nothing is known about E7. Studies on mucosal HPV types (e.g. HPV16) showed that E7 deregulates the cell cycle by binding to and promoting degradation of retinoblastoma protein (pRb). Here, we characterized the impact of HPV77 E7 on the cell cycle. We observed that HPV77 E7 associated with pRb with a lower affinity than HPV16 E7, promoting weakly its degradation. Although, HPV16 E7 led to cellular proliferation and accumulation of the cell cycle inhibitor p16(INK4a), both events were not clearly observed in HPV77 E7 cells. Together, these data indicate that HPV77 E7 does not efficiently deregulate the cell cycle, in contrast to several E7s of mucosal HPV types.

Agonist immunotherapy restores T cell function following MEK inhibition improving efficacy in breast cancer.

The presence of tumor-infiltrating lymphocytes in triple-negative breast cancers is correlated with improved outcomes. Ras/MAPK pathway activation is associated with significantly lower levels of tumor-infiltrating lymphocytes in triple-negative breast cancers and while MEK inhibition can promote recruitment of tumor-infiltrating lymphocytes to the tumor, here we show that MEK inhibition adversely affects early onset T-cell effector function. We show that α-4-1BB and α-OX-40 T-cell agonist antibodies can rescue the adverse effects of MEK inhibition on T cells in both mouse and human T cells, which results in augmented anti-tumor effects in vivo. This effect is dependent upon increased downstream p38/JNK pathway activation. Taken together, our data suggest that although Ras/MAPK pathway inhibition can increase tumor immunogenicity, the negative impact on T-cell activity is functionally important. This undesirable impact is effectively prevented by combination with T-cell immune agonist immunotherapies resulting in superior therapeutic efficacy.MEK inhibition in breast cancer is associated with increased tumour infiltrating lymphocytes (TILs), however, MAPK activity is required for T cells function. Here the authors show that TILs activity following MEK inhibition can be enhanced by agonist immunotherapy resulting in synergic therapeutic effects.

Combined immune checkpoint blockade as a therapeutic strategy for BRCA1-mutated breast cancer.

Immune checkpoint inhibitors have emerged as a potent new class of anticancer therapy. They have changed the treatment landscape for a range of tumors, particularly those with a high mutational load. To date, however, modest results have been observed in breast cancer, where tumors are rarely hypermutated. Because BRCA1-associated tumors frequently exhibit a triple-negative phenotype with extensive lymphocyte infiltration, we explored their mutational load, immune profile, and response to checkpoint inhibition in a Brca1-deficient tumor model. BRCA1-mutated triple-negative breast cancers (TNBCs) exhibited an increased somatic mutational load and greater numbers of tumor-infiltrating lymphocytes, with increased expression of immunomodulatory genes including PDCD1 (PD-1) and CTLA4, when compared to TNBCs from BRCA1-wild-type patients. Cisplatin treatment combined with dual anti-programmed death-1 and anti-cytotoxic T lymphocyte-associated antigen 4 therapy substantially augmented antitumor immunity in Brca1-deficient mice, resulting in an avid systemic and intratumoral immune response. This response involved enhanced dendritic cell activation, reduced suppressive FOXP3+ regulatory T cells, and concomitant increase in the activation of tumor-infiltrating cytotoxic CD8+ and CD4+ T cells, characterized by the induction of polyfunctional cytokine-producing T cells. Dual (but not single) checkpoint blockade together with cisplatin profoundly attenuated the growth of Brca1-deficient tumors in vivo and improved survival. These findings provide a rationale for clinical studies of combined immune checkpoint blockade in BRCA1-associated TNBC.

The E3-ligase E6AP Represses Breast Cancer Metastasis via Regulation of ECT2-Rho Signaling.

Metastatic disease is the major cause of breast cancer-related death and despite many advances, current therapies are rarely curative. Tumor cell migration and invasion require actin cytoskeletal reorganization to endow cells with capacity to disseminate and initiate the formation of secondary tumors. However, it is still unclear how these migratory cells colonize distant tissues to form macrometastases. The E6-associated protein, E6AP, acts both as an E3 ubiquitin-protein ligase and as a coactivator of steroid hormone receptors. We report that E6AP suppresses breast cancer invasiveness, colonization, and metastasis in mice, and in breast cancer patients, loss of E6AP associates with poor prognosis, particularly for basal breast cancer. E6AP regulates actin cytoskeletal remodeling via regulation of Rho GTPases, acting as a negative regulator of ECT2, a GEF required for activation of Rho GTPases. E6AP promotes ubiquitination and proteasomal degradation of ECT2 for which high expression predicts poor prognosis in breast cancer patients. We conclude that E6AP suppresses breast cancer metastasis by regulating actin cytoskeleton remodeling through the control of ECT2 and Rho GTPase activity. These findings establish E6AP as a novel suppressor of metastasis and provide a compelling rationale for inhibition of ECT2 as a therapeutic approach for patients with metastatic breast cancer. Cancer Res; 76(14); 4236-48. ©2016 AACR.

Human papillomavirus type 16 E6 inhibits p21(WAF1) transcription independently of p53 by inactivating p150(Sal2).

HPV16 E6 deregulates G1/S cell cycle progression through p53 degradation preventing transcription of the CDK inhibitor p21(WAF1). However, additional mechanisms independent of p53 inactivation appear to exist. Here, we report that HPV16 E6 targets the cellular factor p150(Sal2), which positively regulates p21(WAF1) transcription. HPV16 E6 associates with p150(Sal2), inducing its functional inhibition by preventing its binding to cis elements on the p21(WAF1) promoter. A HPV16 E6 mutant, L110Q, which was unable to bind p150(Sal2), did not affect the ability of the cellular protein to bind p21(WAF1) promoter, underlining the linkage between these events. These data describe a novel mechanism by which HPV16 E6 induces cell cycle deregulation with a p53-independent pathway. The viral oncoprotein targets p150(Sal2), a positive transcription regulator of p21(WAF1) gene, preventing G1/S arrest and allowing cellular proliferation and efficient viral DNA replication.