Prolactinoma ErbB receptor expression and targeted therapy for aggressive tumors.
ABSTRACT: As ErbB signaling is a determinant of prolactin synthesis, role of ErbB receptors was tested for prolactinoma outcomes and therapy. The objective of this study was to characterize ErbB receptor expression in prolactinomas and then perform a pilot study treating resistant prolactinomas with a targeted tyrosine kinase inhibitor (TKI). Retrospective analysis of prolactinomas and pilot study for dopamine agonist resistant prolactinomas in tertiary referral center. We performed immunofluorescent staining of a tissue array of 29 resected prolactinoma tissues for EGFR, ErbB2, ErbB3, and ErbB4 correlated with clinical features. Two patients with aggressive resistant prolactinomas enrolled and completed trial. They received lapatinib 1,250 mg daily for 6 months with tumor and hormone assessments. Main outcome measures were positive tumor staining of respective ErbB receptors, therapeutic reduction of prolactin levels and tumor shrinkage. Treated PRL levels and tumor volumes were suppressed in both subjects treated with TKI. EGFR expression was positive in 82 % of adenomas, ErbB2 in 92 %, ErbB3 in 25 %, and ErbB4 in 71 %, with ErbB2 score > EGFR > ErbB4 > ErbB3. Higher ErbB3 expression was associated with optic chiasm compression (p = 0.03), suprasellar extension (p = 0.04), and carotid artery encasement (p = 0.01). Higher DA response rates were observed in tumors with higher ErbB3 expression. Prolactinoma expression of specific ErbB receptors is associated with tumor invasion, symptoms, and response to dopamine agonists. Targeting ErbB receptors may be effective therapy in patients with resistant prolactinomas.
Project description:ErbB receptors (EGFR (ErbB1), ErbB2, ErbB3, and ErbB4) are important regulators of normal growth and differentiation, and they are involved in the pathogenesis of cancer. Following ligand binding and receptor activation, EGFR is endocytosed and transported to lysosomes where the receptor is degraded. This downregulation of EGFR is a complex and tightly regulated process. The functions of ErbB2, ErbB3, and ErbB4 are also regulated by endocytosis to some extent, although the current knowledge of these processes is sparse. Impaired endocytic downregulation of signaling receptors is frequently associated with cancer, since it can lead to increased and uncontrolled receptor signaling. In this review we describe the current knowledge of ErbB receptor endocytic downregulation. In addition, we outline how ErbB receptors can escape endocytic downregulation in cancer, and we discuss how targeted anti-cancer therapy may induce endocytic downregulation of ErbB receptors.
Project description:Ovarian cancer is the leading cause of death from gynecologic cancers in the United States. Failure may be due to variable expression and/or complex interactions of growth factor receptors in individual tumors. As ErbB3-MET cooperativity is implicated in solid tumor resistance to EGFR/ErbB2 inhibitors, we evaluated expression of MET and all 4 ErbB family members in ovarian cancers. Tissue arrays were prepared from archival formalin-fixed paraffin-embedded tumor samples, including 202 ovarian carcinomas (Stage I-IV) and controls. Of 202 patient samples, only 25% were positive for EGFR and 35% for ErbB2 expression. ErbB3, ErbB4, and MET showed marked expression in 76%, 98%, and 96% of cases. Consistent with high incidence, there was no significant correlation for expression of ErbB3, ErbB4, or MET with outcome. On the basis of their high expression in the majority of cases, inhibitors targeting ErbB3, ErbB4, and/or MET may be broadly applicable as therapeutic agents in this disease.
Project description:ErbB3/HER3 is one of four members of the human epidermal growth factor receptor (EGFR/HER) or ErbB receptor tyrosine kinase family. ErbB3 binds neuregulins via its extracellular region and signals primarily by heterodimerizing with ErbB2/HER2/Neu. A recently appreciated role for ErbB3 in resistance of tumor cells to EGFR/ErbB2-targeted therapeutics has made it a focus of attention. However, efforts to inactivate ErbB3 therapeutically in parallel with other ErbB receptors are challenging because its intracellular kinase domain is thought to be an inactive pseudokinase that lacks several key conserved (and catalytically important) residues-including the catalytic base aspartate. We report here that, despite these sequence alterations, ErbB3 retains sufficient kinase activity to robustly trans-autophosphorylate its intracellular region--although it is substantially less active than EGFR and does not phosphorylate exogenous peptides. The ErbB3 kinase domain binds ATP with a K(d) of approximately 1.1 microM. We describe a crystal structure of ErbB3 kinase bound to an ATP analogue, which resembles the inactive EGFR and ErbB4 kinase domains (but with a shortened alphaC-helix). Whereas mutations that destabilize this configuration activate EGFR and ErbB4 (and promote EGFR-dependent lung cancers), a similar mutation conversely inactivates ErbB3. Using quantum mechanics/molecular mechanics simulations, we delineate a reaction pathway for ErbB3-catalyzed phosphoryl transfer that does not require the conserved catalytic base and can be catalyzed by the "inactive-like" configuration observed crystallographically. These findings suggest that ErbB3 kinase activity within receptor dimers may be crucial for signaling and could represent an important therapeutic target.
Project description:Therapies targeting ERBB2 have shown success in the clinic. However, response is not determined solely by expression of ERBB2. Levels of ERBB3, its preferred heterodimerisation partner and ERBB ligands may also have a role.We measured NRG1 expression by real-time quantitative RT-PCR and ERBB receptors by western blotting and immunohistochemistry in bladder tumours and cell lines.NRG1? and NRG1? showed significant coordinate expression. NRG1? was upregulated in 78% of cell lines. In tumours, there was a greater range of expression with a trend towards increased NRG1? with higher stage and grade. Increased expression of ERBB proteins was detected in 15% (EGFR), 20% (ERBB2), 41% (ERBB3) and 0% (ERBB4) of cell lines. High EGFR expression was detected in 28% of tumours, associated with grade and stage (P=0.05; P=0.04). Moderate or high expression of ERBB2 was detected in 22% and was associated with stage (P=0.025). Cytoplasmic ERBB3 was associated with high tumour grade (P=0.01) and with ERBB2 positivity. In cell lines, NRG1? expression was significantly inversely related to ERBB3, but this was not confirmed in tumours.There is a wide spectrum of NRG1 and ERBB receptor expression in bladder cancer. In advanced tumours, EGFR, ERBB2 and ERBB3 upregulation is common and there is a relationship between expression of ERBB2 and ERBB3 but not the NRG1 ligand.
Project description:The human ErbB family of receptor tyrosine kinases comprises the epidermal growth factor receptor (EGFR/ErbB1/HER1), ErbB2 (HER2/Neu), ErbB3 (HER3), and ErbB4 (HER4). ErbBs play fundamental roles in cell growth and differentiation events in embryonic and adult tissues, and inappropriate ErbB activity has been implicated in several human cancers. We report here the 2.4 A crystal structure of the extracellular region of human ErbB4 in the absence of ligand and show that it adopts a tethered conformation similar to inactive forms of ErbB1 and ErbB3. This structure completes the gallery of unliganded ErbB receptors and demonstrates that all human ligand-binding ErbBs adopt the autoinhibited conformation. We also show that the binding of neuregulin-1beta to ErbB4 and ErbB3 and the binding of betacellulin to both ErbB4 and ErbB1 does not decrease at low pH, unlike the binding of epidermal growth factor and transforming growth factor-alpha to ErbB1. These results indicate an important role for ligand in determining pH-dependent binding and may explain different responses observed when the same ErbB receptor is stimulated by different ligands.
Project description:Background:Somatic mutations in the ERBB genes (epidermal growth factor receptor: EGFR, ERBB2, ERBB3, ERBB4) promote oncogenesis and lapatinib resistance in metastatic HER2+ (human epidermal growth factor-like receptor 2) breast cancer in vitro. Our study aimed to determine the frequency of mutations in four genes: EGFR, ERBB2, ERBB3 and ERBB4 and to investigate whether these mutations affect cellular behaviour and therapy response in vitro and outcomes after adjuvant trastuzumab-based therapy in clinical samples. Methods:We performed Agena MassArray analysis of 227 HER2+ breast cancer samples to identify the type and frequency of ERBB family mutations. Of these, two mutations, the somatic mutations ERBB4-V721I and ERBB4-S303F, were stably transfected into HCC1954 (PIK3CA mutant), HCC1569 (PIK3CA wildtype) and BT474 (PIK3CA mutant, ER positive) HER2+ breast cancer cell lines for functional in vitro experiments. Results:A total of 12 somatic, likely deleterious mutations in the kinase and furin-like domains of the ERBB genes (3 EGFR, 1 ERBB2, 3 ERBB3, 5 ERBB4) were identified in 7% of HER2+ breast cancers, with ERBB4 the most frequently mutated gene. The ERBB4-V721I kinase domain mutation significantly increased 3D-colony formation in 3/3 cell lines, whereas ERBB4-S303F did not increase growth rate or 3D colony formation in vitro. ERBB4-V721I sensitized HCC1569 cells (PIK3CA wildtype) to the pan class I PI3K inhibitor copanlisib but increased resistance to the pan-HER family inhibitor afatinib. The combinations of copanlisib with trastuzumab, lapatinib, or afatinib remained synergistic regardless of ERBB4-V721I or ERBB4-S303F mutation status. Conclusions:ERBB gene family mutations, which are present in 7% of our HER2+ breast cancer cohort, may have the potential to alter cellular behaviour and the efficacy of HER- and PI3K-inhibition.
Project description:The first three members of the ErbB family of receptor tyrosine kinases activate a wide variety of signaling pathways and are frequently misregulated in cancer. Much less is known about ErbB4. Here we use tandem mass spectrometry to identify 19 sites of tyrosine phosphorylation on ErbB4, and protein microarrays to quantify biophysical interactions between these sites and virtually every SH2 and PTB domain encoded in the human genome. Our unbiased approach highlighted several previously unrecognized interactions and led to the finding that ErbB4 can recruit and activate STAT1. At a systems level, we found that ErbB4 is much more selective than the other ErbB receptors. This suggests that ErbB4 may enable ErbB2 and ErbB3 to signal independently of EGFR under normal conditions, and provides a possible explanation for the protective properties of ErbB4 in cancer.
Project description:ErbB4 (HER4) is a member of the ErbB family of receptor tyrosine kinases, which includes the Epidermal Growth Factor Receptor (EGFR/ErbB1), ErbB2 (HER2/Neu), and ErbB3 (HER3). Mounting evidence indicates that ErbB4, unlike EGFR or ErbB2, functions as a tumor suppressor in many human malignancies. Previous analyses of the constitutively-dimerized and -active ErbB4 Q646C mutant indicate that ErbB4 kinase activity and phosphorylation of ErbB4 Tyr1056 are both required for the tumor suppressor activity of this mutant in human breast, prostate, and pancreatic cancer cell lines. However, the cytoplasmic region of ErbB4 possesses additional putative functional motifs, and the contributions of these functional motifs to ErbB4 tumor suppressor activity have been largely underexplored. Here we demonstrate that ErbB4 BH3 and LXXLL motifs, which are thought to mediate interactions with Bcl family proteins and steroid hormone receptors, respectively, are required for the tumor suppressor activity of the ErbB4 Q646C mutant. Furthermore, abrogation of the site of ErbB4 cleavage by gamma-secretase also disrupts the tumor suppressor activity of the ErbB4 Q646C mutant. This last result suggests that ErbB4 cleavage and subcellular trafficking of the ErbB4 cytoplasmic domain may be required for the tumor suppressor activity of the ErbB4 Q646C mutant. Indeed, here we demonstrate that mutants that disrupt ErbB4 kinase activity, ErbB4 phosphorylation at Tyr1056, or ErbB4 cleavage by gamma-secretase also disrupt ErbB4 trafficking away from the plasma membrane and to the cytoplasm. This supports a model for ErbB4 function in which ErbB4 tumor suppressor activity is dependent on ErbB4 trafficking away from the plasma membrane and to the cytoplasm, mitochondria, and/or the nucleus.
Project description:Pharmacologic blockade of EGFR or the closely related receptor ERBB2 has modest efficacy against colorectal cancers in the clinic. Although the upregulation of ERBB3, a pseudo-kinase member of the EGFR/ERBB family, is known to contribute to EGFR inhibitor resistance in other cancers, its functions in normal and malignant intestinal epithelium have not been defined. We have shown here that the intestinal epithelium of mice with intestine-specific genetic ablation of Erbb3 exhibits no cytological abnormalities but does exhibit loss of expression of ERBB4 and sensitivity to intestinal damage. By contrast, intestine-specific Erbb3 ablation resulted in almost complete absence of intestinal tumors in the ApcMin mouse model of colon cancer. Unlike nontransformed epithelium lacking ERBB3, intestinal tumors lacking ERBB3 had reduced PI3K/AKT signaling, which led to attenuation of tumorigenesis via a tumor-specific increase in caspase-3-mediated apoptosis. Consistent with the mouse data, which suggest that ERBB3-ERBB4 heterodimers contribute to colon cancer survival, experimentally induced loss of ERBB3 in a KRAS mutant human colon cancer cell line was associated with loss of ERBB4 expression, and siRNA knockdown of either ERBB3 or ERBB4 resulted in elevated levels of apoptosis. These results indicate that the ERBB3 pseudo-kinase has essential roles in supporting intestinal tumorigenesis and suggest that ERBB3 may be a promising target for the treatment of colorectal cancers.
Project description:Recently, the epidermal growth factor (EGF) receptor (EGFR), a member of the ErbB receptor family, and its down-stream signalling have been identified as co-factors for HCV entry and replication. Since EGFR also functions as a heterodimer with other ErbB receptor family members, the subject of the present study was to investigate a possible viral interference with these cellular components. By using genotype 1b replicon cells as well as an infection-based system we found that while transcript and protein levels of EGFR and ErbB2 were up-regulated or unaffected, respectively, HCV induced a substantial reduction of ErbB3 and ErbB4 expression. Down-regulation of ErbB3 expression by HCV involves specificity protein (Sp)1-mediated induction of Neuregulin (NRG)1 expression as well as activation of Akt. Consistently, at transcript level disruption of ErbB3 expression by HCV can be prevented by knockdown of NRG1 or Sp1 expression, whereas reconstitution of ErbB3 protein levels requires inhibition of HCV-induced NRG1 expression and of Akt activity. Interestingly, the NRG1-mediated suppression of ErbB3 expression by HCV results in an enhanced expression of EGFR and ErbB2 on the cell surface, which can be mimicked by siRNA-mediated knockdown of ErbB3 expression. These data delineate a novel mechanism enabling HCV to sway the composition of the ErbB family members on the surface of its host cell by an NRG1-driven circuit and unravels a yet unknown cross-regulation between ErbB3 and the two other family members ErbB2 and EGFR. The shift of the receptor surface expression of the ErbB family towards enhanced expression of ErbB2 and EGFR triggered by HCV was found to promote viral RNA replication and infectivity. This suggests that HCV rearranges expression of ErbB family members to adapt the cellular environment to its requirements.