Glucocorticoid receptor-induced non-muscle caldesmon regulates metastasis in castration-resistant prostate cancer.

Lethal prostate cancer (PCa) is characterized by the presence of metastases and development of resistance to therapies. Metastases form in a multi-step process enabled by dynamic cytoskeleton remodeling. An actin cytoskeleton regulating gene, CALD1, encodes a protein caldesmon (CaD). Its isoform, low-molecular-weight CaD (l-CaD), operates in non-muscle cells, supporting the function of filaments involved in force production and mechanosensing. Several factors, including glucocorticoid receptor (GR), have been identified as regulators of l-CaD in different cell types, but the regulation of l-CaD in PCa has not been defined. PCa develops resistance in response to therapeutic inhibition of androgen signaling by multiple strategies. Known strategies include androgen receptor (AR) alterations, modified steroid synthesis, and bypassing AR signaling, for example, by GR upregulation. Here, we report that in vitro downregulation of l-CaD promotes epithelial phenotype and reduces spheroid growth in 3D, which is reflected in vivo in reduced formation of metastases in zebrafish PCa xenografts. In accordance, CALD1 mRNA expression correlates with epithelial-to-mesenchymal transition (EMT) transcripts in PCa patients. We also show that CALD1 is highly co-expressed with GR in multiple PCa data sets, and GR activation upregulates l-CaD in vitro. Moreover, GR upregulation associates with increased l-CaD expression after the development of resistance to antiandrogen therapy in PCa xenograft mouse models. In summary, GR-regulated l-CaD plays a role in forming PCa metastases, being clinically relevant when antiandrogen resistance is attained by the means of bypassing AR signaling by GR upregulation.

Effect of caldesmon mutations in the development of zebrafish embryos.

Cancer is a profound medical concern and better treatments are needed for cancer patients. Therefore, new cancer targets are constantly being studied. These targets need not only be relevant for cancer progression, but their modulation needs to be tolerated reasonably well by the host. Caldesmon is one of these proposed novel targets for cancer therapy. Therefore, we analyzed effects of caldesmon mutations in normal development using genetically modified zebrafish embryos. We analyzed mutations in both zebrafish caldesmon genes, cald1a and cald1b and analyzed effects of either mutation alone or as in combination in double homozygous embryos using molecular, morphological and functional analyses. The effects of caldesmon mutations were mild and the gross development of zebrafish embryos was normal. The caldesmon mutant embryos had, however, alterations in response to light-stimulus in behavioural assays. Taken together, the effects of caldesmon mutations in the development of zebrafish embryos were reasonably well tolerated and did not indicate significant concerns for caldesmon being a potential target for cancer therapy.

Radium-223 dichloride treatment in metastatic castration-resistant prostate cancer in Finland: A real-world evidence multicenter study.

BACKGROUND: Radium-233 dichloride is an alpha emitter that specifically targets bone metastases in prostate cancer. Results of a previously reported phase III randomized trial showed survival benefit for radium-223 compared to best supportive care in castration-resistant prostate cancer (CRPC) with bone metastases. However, real-world data are also needed with wider inclusion criteria. METHODS: We report results of a retrospective multicenter study including all patients with metastatic CRPC treated with radium-223 in all five university hospitals in Finland since the introduction of the treatment. We identified 160 patients who had received radium-223 in Finland in 2014-2019. RESULTS: The median overall survival (OS) was 13.8 months (range 0.5-57 months), and the median real-world progression-free survival (rwPFS) was 4.9 months (range 0.5-29.8 months). Alkaline phosphatase (ALP) values within the normal range before and during the radium-223 treatment or the reduction of elevated ALP to normal range during treatment were associated with better OS when compared to elevated ALP values before and during treatment (p < 0.0001). High prostate-specific antigen (PSA) level (≥100 µg/L) before radium-223 treatment was associated with poor OS compared to low PSA level (<20 µg/L) (p = 0.0001). Most patients (57%) experienced pain relief. Pain relief indicated better OS (p = 0.002). Radium-223 treatment was well tolerated. Toxicity was mostly low grade. Only 12.5% of the patients had grade III-IV adverse events, most commonly anemia, neutropenia, leucopenia, and thrombocytopenia. CONCLUSION: Radium-223 was well tolerated in routine clinical practice, and most patients achieved pain relief. Pain relief, ALP normalization, lower baseline PSA, and PSA decrease during radium-223 treatment were prognostic for better survival. The efficacy of radium-223 in mCRPC as estimated using OS was comparable to earlier randomized trial in this retrospective real-world study. Our results support using radium-223 for mCRPC patients with symptomatic bone metastases even in the era of new-generation androgen receptor-targeted agents.

TSPO is a potential independent prognostic factor associated with cellular respiration and p16 in head and neck squamous cell carcinoma.

Background: Treatment resistance and relapse are common problems in head and neck squamous cell carcinoma (HNSCC). Except for p16, no clinically accepted prognostic biomarkers are available for HNSCC. New biomarkers predictive of recurrence and survival are crucial for optimal treatment planning and patient outcome. High translocator protein (TSPO) levels have been associated with poor survival in cancer, but the role of TSPO has not been extensively evaluated in HNSCC. Materials and methods: TSPO expression was determined in a large population-based tissue microarray cohort including 611 patients with HNSCC and evaluated for survival in several clinicopathological subgroups. A TCGA HNSCC cohort was used to further analyze the role of TSPO in HNSCC. Results: TSPO expression was downregulated in more aggressive tumors. Low TSPO expression associated with worse 5-year survival and was an independent prognostic factor for disease-specific survival. Subgroup analyses showed that low TSPO expression associated with worse survival particularly in p16-positive oropharyngeal cancer. In silico analyses supported the prognostic role of TSPO. Cellular respiration had the highest significance in pathway analyses for genes expressed positively with TSPO. Conclusion: Decreased TSPO expression associates with poor prognosis in HNSCC. TSPO is a prognostic biomarker in HNSCC to potentially guide treatment stratification especially in p16-positive oropharyngeal cancer.

Therapeutic Potential of Targeting the SUMO Pathway in Cancer.

SUMOylation is a dynamic and reversible post-translational modification, characterized more than 20 years ago, that regulates protein function at multiple levels. Key oncoproteins and tumor suppressors are SUMO substrates. In addition to alterations in SUMO pathway activity due to conditions typically present in cancer, such as hypoxia, the SUMO machinery components are deregulated at the genomic level in cancer. The delicate balance between SUMOylation and deSUMOylation is regulated by SENP enzymes possessing SUMO-deconjugation activity. Dysregulation of SUMO machinery components can disrupt the balance of SUMOylation, contributing to the tumorigenesis and drug resistance of various cancers in a context-dependent manner. Many molecular mechanisms relevant to the pathogenesis of specific cancers involve SUMO, highlighting the potential relevance of SUMO machinery components as therapeutic targets. Recent advances in the development of inhibitors targeting SUMOylation and deSUMOylation permit evaluation of the therapeutic potential of targeting the SUMO pathway in cancer. Finally, the first drug inhibiting SUMO pathway, TAK-981, is currently also being evaluated in clinical trials in cancer patients. Intriguingly, the inhibition of SUMOylation may also have the potential to activate the anti-tumor immune response. Here, we comprehensively and systematically review the recent developments in understanding the role of SUMOylation in cancer and specifically focus on elaborating the scientific rationale of targeting the SUMO pathway in different cancers.

More Than Meets the Eye: Scientific Rationale behind Molecular Imaging and Therapeutic Targeting of Prostate-Specific Membrane Antigen (PSMA) in Metastatic Prostate Cancer and Beyond.

Prostate cancer is the second most common cancer type in men globally. Although the prognosis for localized prostate cancer is good, no curative treatments are available for metastatic disease. Better diagnostic methods could help target therapies and improve the outcome. Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein that is overexpressed on malignant prostate tumor cells and correlates with the aggressiveness of the disease. PSMA is a clinically validated target for positron emission tomography (PET) imaging-based diagnostics in prostate cancer, and during recent years several therapeutics have been developed based on PSMA expression and activity. The expression of PSMA in prostate cancer can be very heterogeneous and some metastases are negative for PSMA. Determinants that dictate clinical responses to PSMA-targeting therapeutics are not well known. Moreover, it is not clear how to manipulate PSMA expression for therapeutic purposes and develop rational treatment combinations. A deeper understanding of the biology behind the use of PSMA would help the development of theranostics with radiolabeled compounds and other PSMA-based therapeutic approaches. Along with PSMA several other targets have also been evaluated or are currently under investigation in preclinical or clinical settings in prostate cancer. Here we critically elaborate the biology and scientific rationale behind the use of PSMA and other targets in the detection and therapeutic targeting of metastatic prostate cancer.

A Public Mental Health Study Among Iraqi Refugees in Sweden: Social Determinants, Resilience, Gender, and Cultural Context.

This public mental health study highlights the interactions among social determinants and resilience on mental health, PTSD and acculturation among Iraqi refugees in Sweden 2012-2013. Objectives: The study aims to understand participants' health, resilience and acculturation, paying specific attention to gender differences. Design: The study, using a convenience sampling survey design (N = 4010, 53.2% men), included measures on social determinants, general health, coping, CD-RISC, selected questions from the EMIC, PC-PTSD, and acculturation. Results: Gender differences and reported differences between life experiences in Iraq and Sweden were strong. In Sweden, religious activity was more widespread among women, whereas activity reflecting religion and spirituality as a coping mechanism decreased significantly among men. A sense of belonging both to a Swedish and an Iraqi ethnic identity was frequent. Positive self-evaluation in personal and social areas and goals in life was strong. The strongest perceived source of social support was from parents and siblings, while support from authorities generally was perceived as low. Self-rated health was high and the incidence of PTSD was low. A clear majority identified multiple social determinants contributing to mental health problems. Social or situational and emotional or developmental explanations were the most common. In general, resilience (as measured with CD-RISC) was low, with women's scores lower than that of men. Conclusions: Vulnerability manifested itself in unemployment after a long period in Sweden, weak social networks outside the family, unsupportive authorities, gender differences in acculturation, and women showing more mental health problems. Though low socially determined personal scores of resilience were found, we also identified a strong level of resilience, when using a culture-sensitive approach and appraising resilience as expressed in coping, meaning, and goals in life. Clinicians need to be aware of the risks of poorer mental health among refugees in general and women in particular, although mental health problems should not be presumed in the individual patient. Instead clinicians need to find ways of exploring the cultural and social worlds and needs of refugee patients. Authorities need to address the described post-migration problems and unmet needs of social support, together comprising the well-established area of the social determinants of health.

Safe but isolated - an interview study with Iraqi refugees in Sweden about social networks, social support, and mental health.

BACKGROUND: Problems with social networks and social support are known to be associated with mental ill-health in refugees. Social support after migration promotes resilience. AIM: To study how Iraqi refugees who arrived in Sweden after the year 2000 perceived their social networks and social support, and to relate the observed network characteristics and changes to the refugees' mental health and well-being. METHOD: Semi-structured interviews with 31 refugees, including questions on background and migration experiences, a biographical network map, and three health assessment scales. The findings were analysed with descriptive statistics and content thematic analysis. RESULTS: The respondents' networks were diminished. Social support was continued to be provided mainly by family members and supplemented by support from authorities. The main themes of the refugee experience of post-migration challenges were weakened social networks, barriers to integration and challenges to cultural and religious belonging. Failed reunion and worrying about relatives was described as particularly painful. Negative contacts with authority persons were often seen as humiliating or discriminating. Acquiring a new cultural belonging was described as challenging. At the same time, changing family and gender roles made it more difficult to preserve and develop the culture of origin. Traumatic experiences and mental health problems were common in this group. Family issues were more often than integration difficulties associated with mental health problems. CONCLUSION: In order to strengthen post-migration well-being and adaptation, authorities should support the refugees' social networks. Clinicians need to address post-migration problems and challenges, including the meaning and function of social networks.

Role of Ubiquitin and SUMO in Intracellular Trafficking.

Precise location of proteins at a given time within a cell is essential to convey specific signals and result in a relevant functional outcome. Small ubiquitin-like modifications, such as ubiquitin and SUMO, represent a delicate and diverse way to transiently regulate intracellular trafficking events of existing proteins in cells. Trafficking of multiple proteins is controlled reversibly by ubiquitin and/or SUMO directly or indirectly via regulation of transport machinery components. Regulation is dynamic and multilayered, involving active crosstalk and interdependence between post-translational modifications. However, in most cases regulation appears very complex, and the mechanistic details regarding how ubiquitin and SUMO control protein location in cells are not yet fully understood. Moreover, most of the findings still lack in vivo evidence in multicellular organisms.

PARP Inhibitors in Prostate Cancer­The Preclinical Rationale and Current Clinical Development.

Prostate cancer is globally the second most commonly diagnosed cancer type in men. Recent studies suggest that mutations in DNA repair genes are associated with aggressive forms of prostate cancer and castration resistance. Prostate cancer with DNA repair defects may be vulnerable to therapeutic targeting by Poly(ADP-ribose) polymerase (PARP) inhibitors. PARP enzymes modify target proteins with ADP-ribose in a process called PARylation and are in particular involved in single strand break repair. The rationale behind the clinical trials that led to the current use of PARP inhibitors to treat cancer was to target the dependence of BRCA-mutant cancer cells on the PARP-associated repair pathway due to deficiency in homologous recombination. However, recent studies have proposed therapeutic potential for PARP inhibitors in tumors with a variety of vulnerabilities generating dependence on PARP beyond the synthetic lethal targeting of BRCA1/BRCA2 mutated tumors, suggesting a wider potential than initially thought. Importantly, PARP-associated DNA repair pathways are also closely connected to androgen receptor (AR) signaling, which is a key regulator of tumor growth and a central therapeutic target in prostate cancer. In this review, we provide an extensive overview of published and ongoing trials exploring PARP inhibitors in treatment of prostate cancer and discuss the underlying biology. Several clinical trials are currently studying PARP inhibitor mono- and combination therapies in the treatment of prostate cancer. Integration of drugs targeting DNA repair pathways in prostate cancer treatment modalities allows developing of more personalized care taking also into account the genetic makeup of individual tumors.

Different responses of colorectal cancer cells to alternative sequences of cetuximab and oxaliplatin.

Therapeutic protocols including EGFR antibodies in the context of oxaliplatin-based regimens have variable clinical effect in colorectal cancer. Here, we tested the effect of the EGFR antibody cetuximab in different sequential combinations with oxaliplatin on the growth of colorectal cancer cells in vitro and in vivo. Cetuximab reduced the efficacy of oxaliplatin when administered before oxaliplatin but provided additive effect when administered after oxaliplatin regardless of the KRAS or BRAF mutation status of the cells. Systemic gene expression and protein phosphorylation screens revealed alternatively activated pathways regulating apoptosis, cell cycle and DNA damage response. Functional assays indicated that cetuximab-induced arrest of the cells into the G1 phase of the cell cycle was associated with reduced responsiveness of the cells to subsequent treatment with oxaliplatin. In contrast, oxaliplatin-enhanced responsiveness to subsequent treatment with cetuximab was associated with increased apoptosis, inhibition of STAT3 activity and increased EGFR down-regulation. This preclinical study indicates that optimizing the sequence of administration may enhance the antitumor effect of combination therapy with EGFR antibodies and oxaliplatin.

Challenges of Combining Perspectives.

BACKGROUND: Asylum seekers have increased risk of suicide and suicidal behavior, with differences related to origin, gender, and age. There are barriers to communication in clinical encounters between asylum seekers and clinicians. There is insufficient knowledge about how communication in the clinical encounter affects the suicide risk in female asylum seekers. AIMS: To explore the documented communication between female asylum-seeking suicide attempters and clinicians and how it affects treatment. METHOD: The medical records of 18 asylum-seeking women who had attempted suicide were analyzed with content analysis. RESULTS: Communication between patients and clinicians was affected by: the unbearable realities of the women; difficulties for clinicians in decoding languages of distress, and understanding trauma and subjective meanings of suicide; challenges of combining patients' and clinicians' perspectives; and a sense of shared powerlessness. LIMITATIONS: The medical records did not give direct access to the patient's experience, only to the patient as documented by the clinician. CONCLUSION: The results suggest that clinicians working with asylum seekers who have attempted suicide need to develop an understanding of social and cultural factors and of trauma issues. A question for further study is how an enhanced integration of context and subjectivity in psychiatric practice would equip clinicians for the specific challenges encountered.

Clinical challenges in cultural psychiatry - searching for meaning, searching for methods†.

BACKGROUND: Mental health services in Sweden are confronted with globalization and refugee migration from conflict- and war-torn countries. AIM: To discuss how clinicians in Sweden can deal with a series of challenges in a changing globalized society, ranging from difficulties of overcoming barriers to help seeking to difficulties of identifying trauma and finding culturally adapted clinical tools. METHOD: Case vignettes are presented to exemplify challenges. Different approaches developed to support clinicians are presented. RESULTS: The concepts of patient centered care and shared decision-making as well as the cultural formulation interview, are recommended to explore the significance of culture and context in psychiatric assessments. Acknowledging relational aspects of care and of paying attention to the patients' social worlds in clinical work is also essential. CONCLUSIONS: The article includes recommendations for training as well as an appeal for the involvement of the wider society in the work to guarantee equitable and high-quality mental health services for some of the most vulnerable patient groups in society.

SUMOylation regulates nuclear accumulation and signaling activity of the soluble intracellular domain of the ErbB4 receptor tyrosine kinase.

Erb-B2 receptor tyrosine kinase 4 (ErbB4) is a kinase that can signal via a proteolytically released intracellular domain (ICD) in addition to classical receptor tyrosine kinase-activated signaling cascades. Previously, we have demonstrated that ErbB4 ICD is posttranslationally modified by the small ubiquitin-like modifier (SUMO) and functionally interacts with the PIAS3 SUMO E3 ligase. However, direct evidence of SUMO modification in ErbB4 signaling has remained elusive. Here, we report that the conserved lysine residue 714 in the ErbB4 ICD undergoes SUMO modification, which was reversed by sentrin-specific proteases (SENPs) 1, 2, and 5. Although ErbB4 kinase activity was not necessary for the SUMOylation, the SUMOylated ErbB4 ICD was tyrosine phosphorylated to a higher extent than unmodified ErbB4 ICD. Mutation of the SUMOylation site compromised neither ErbB4-induced phosphorylation of the canonical signaling pathway effectors Erk1/2, Akt, or STAT5 nor ErbB4 stability. In contrast, SUMOylation was required for nuclear accumulation of the ErbB4 ICD. We also found that Lys-714 was located within a leucine-rich stretch, which resembles a nuclear export signal, and could be inactivated by site-directed mutagenesis. Furthermore, SUMOylation modulated the interaction of ErbB4 with chromosomal region maintenance 1 (CRM1), the major nuclear export receptor for proteins. Finally, the SUMO acceptor lysine was functionally required for ErbB4 ICD-mediated inhibition of mammary epithelial cell differentiation in a three-dimensional cell culture model. Our findings indicate that a SUMOylation-mediated mechanism regulates nuclear localization and function of the ICD of ErbB4 receptor tyrosine kinase.

Assessment and treatment of asylum seekers after a suicide attempt: a comparative study of people registered at mental health services in a Swedish location.

BACKGROUND: Even though asylum seekers are considered vulnerable to mental ill-health, knowledge of their suicidal behaviour is limited. The aim of this study was to improve our understanding of factors that influence the clinical assessment of asylum seekers who have attempted suicide compared to the assessment of non-asylum seekers. METHODS: The study focused on 88 asylum seekers registered for suicide attempts in mental health services 2005-2009, who were matched for age and gender and compared with 88 suicide attempters with Swedish personal identity numbers. The medical records were analysed with a quantitative protocol, focusing on social risk and protective factors, health history, current clinical picture as well as the assessment procedure, diagnostics, patterns of treatment and follow-up in this clinical group. Data was analysed using the chi-square test, Fisher's exact probability test, and the Mann-Whitney U test. RESULTS: As in earlier studies, asylum seekers were more traumatized, had different social risk factors and received different diagnoses than the controls. Asylum seekers were referred to less specialized follow-up after treatment, in spite of their health history and of previous and current clinical pictures indicating a similar or--in the case of the female asylum seekers--more serious mental health condition. Female asylum seekers also received more intense and prolonged in-patient treatment than female controls. Asylum seekers appeared to have social networks more often than the control group. However, there was less documentation of the social context, previous suicidal behaviour, and on suicide in the family and close environment of the asylum-seeking men. Information on suicidal intent was lacking in a majority of both groups. The time relation of the suicide attempt and the asylum process suggested the importance of the asylum decision, as well as the possible role of earlier mental health problems and premigration stress, for the suicidal behaviour. CONCLUSIONS: The groups had different sets of risk factors and clinical pictures. There was a lack of early and thorough exploration of suicide intent for both groups, and of contextual and subjective factors for the asylum seekers. Differences in follow-up indicate unequal access to care.

ERBB4 promoter polymorphism is associated with poor distant disease-free survival in high-risk early breast cancer.

A number of genetic variants have been linked to increased risk of breast cancer. Little is, however, known about the prognostic significance of hereditary factors. Here, we investigated the frequency and prognostic significance of two ERBB4 promoter region variants, -782G>T (rs62626348) and -815A>T (rs62626347), in a cohort of 1010 breast cancer patients. The frequency of nine previously described somatic ERBB4 kinase domain mutations was also analyzed. Clinical material used in the study consisted of samples from the phase III, adjuvant, FinHer breast cancer trial involving 1010 women. Tumor DNA samples were genotyped for ERBB4 variants and somatic mutations using matrix-assisted laser desorption ionization/time of flight mass spectrometry. Paraffin-embedded tumor sections from all patients were immunohistochemically stained for ErbB4 expression. Association of ERBB4 genotype to distant disease-free survival (DDFS) was assessed using Kaplan-Meier and Cox regression analyses. Genotyping was successful for 91-93% of the 1010 samples. Frequencies observed for the ERBB4 variants were 2.5% and 1.3% for -782G>T and -815A>T, respectively. Variant -815A>T was significantly associated with poor survival (HR  = 2.86 [95% CI 1.15-6.67], P = 0.017). In contrast, variant -782G>T was associated with well-differentiated cancer (P = 0.019). Two (0.2%) ERBB4 kinase domain mutations were found, both of which have previously been shown to be functional and promote cancer cell growth in vitro. These data present the germ-line ERBB4 variant -815A>T as a novel prognostic marker in high-risk early breast cancer and indicate the presence of rare but potentially oncogenic somatic ERBB4 mutations in breast cancer.

A metabolic prosurvival role for PML in breast cancer.

Cancer cells exhibit an aberrant metabolism that facilitates more efficient production of biomass and hence tumor growth and progression. However, the genetic cues modulating this metabolic switch remain largely undetermined. We identified a metabolic function for the promyelocytic leukemia (PML) gene, uncovering an unexpected role for this bona fide tumor suppressor in breast cancer cell survival. We found that PML acted as both a negative regulator of PPARγ coactivator 1A (PGC1A) acetylation and a potent activator of PPAR signaling and fatty acid oxidation. We further showed that PML promoted ATP production and inhibited anoikis. Importantly, PML expression allowed luminal filling in 3D basement membrane breast culture models, an effect that was reverted by the pharmacological inhibition of fatty acid oxidation. Additionally, immunohistochemical analysis of breast cancer biopsies revealed that PML was overexpressed in a subset of breast cancers and enriched in triple-negative cases. Indeed, PML expression in breast cancer correlated strikingly with reduced time to recurrence, a gene signature of poor prognosis, and activated PPAR signaling. These findings have important therapeutic implications, as PML and its key role in fatty acid oxidation metabolism are amenable to pharmacological suppression, a potential future mode of cancer prevention and treatment.

Protein inhibitor of activated STAT3 (PIAS3) protein promotes SUMOylation and nuclear sequestration of the intracellular domain of ErbB4 protein.

ErbB4 is a receptor tyrosine kinase implicated in the development and homeostasis of the heart, central nervous system, and mammary gland. Cleavable isoforms of ErbB4 release a soluble intracellular domain (ICD) that can translocate to the nucleus and function as a transcriptional coregulator. In search of regulatory mechanisms of ErbB4 ICD function, we identified PIAS3 as a novel interaction partner of ErbB4 ICD. In keeping with the small ubiquitin-like modifier (SUMO) E3 ligase function of protein inhibitor of activated STAT (PIAS) proteins, we showed that the ErbB4 ICD is modified by SUMO, and that PIAS3 stimulates the SUMOylation. Upon overexpression of PIAS3, the ErbB4 ICD generated from the full-length receptor accumulated into the nucleus in a manner that was dependent on the functional nuclear localization signal of ErbB4. In the nucleus, ErbB4 colocalized with PIAS3 and SUMO-1 in promyelocytic leukemia nuclear bodies, nuclear domains involved in regulation of transcription. Accordingly, PIAS3 overexpression had an effect on the transcriptional coregulatory activity of ErbB4, repressing its ability to coactivate transcription with Yes-associated protein. Finally, knockdown of PIAS3 with siRNA partially rescued the inhibitory effect of the ErbB4 ICD on differentiation of MDA-MB-468 breast cancer and HC11 mammary epithelial cells. Our findings illustrate that PIAS3 is a novel regulator of ErbB4 receptor tyrosine kinase, controlling its nuclear sequestration and function.

Function of ERBB4 is determined by alternative splicing.

Alternative splicing is a central tool  of evolution that significantly increases the size of transcriptomes and generates functional specification. Within the human ERBB receptor gene family, only ERBB4 is known to produce functionally distinct isoforms as a result of alternative splicing. While ErbB4 signaling has been demonstrated to regulate cellular processes involved in embryogenesis, carcinogenesis and cardiovascular and psychiatric diseases, relatively little is known about the contribution of the individual isoforms in the different biological contexts. Here, we review recent findings as well as provide novel data about the distribution and functions of the ERBB4 splice variants. These observations represent an example of how minor alterations in the transcripts of a single gene can result in even antagonistic cellular responses. The observations also underline the significance of understanding the unique functions of isoforms of a potential drug target gene.