Adherence to adjuvant endocrine therapy for breast cancer: a qualitative exploration of attribution of symptoms among post-menopausal women

PURPOSE

Oral adjuvant endocrine therapy (AET) is an effective treatment for hormone receptor positive breast cancer to decrease recurrence and mortality, but adherence is poor. This study explored post-menopausal women's experiences with AET, with a particular focus on adherence to AET as well as distress and symptoms experienced prior to and during AET treatment.

METHODS

Participants were recruited from a hospital registry, stratified by adherence to/discontinuation of AET. Telephone interviews followed a semi-structured interview guide and were recorded and transcribed verbatim. Transcripts were systematically coded using team-based coding, with analysis of themes using a grounded theory approach.

RESULTS

Thirty-three participants were interviewed; ages ranged from 57 to 86 years. Participants included 10 discontinued patients and 23 patients who completed their AET course or were adherent to AET at the time of interviewing. Both adherent and discontinued patients reported symptoms throughout their AET treatment course, and both attributed symptoms to factors other than AET (e.g., older age and pre-existing comorbidities). However, discontinued patients were more likely to attribute symptoms to AET and to describe difficulty managing their symptoms, with some directly citing symptoms as the reason for discontinuing AET therapy. Conversely, adherent patients were more likely to describe the necessity of taking AET, despite symptoms.

CONCLUSIONS

AET adherence was associated with beliefs about AET, symptom attribution, and symptom management. Routine symptom monitoring during AET and addressing both symptoms and patients' understanding of their symptoms may promote adherence to AET.

Complex N-Linked Glycosylation: A Potential Modifier of Niemann-Pick Disease, Type C1 Pathology

Complex asparagine-linked glycosylation plays key roles in cellular functions, including cellular signaling, protein stability, and immune response. Previously, we characterized the appearance of a complex asparagine-linked glycosylated form of lysosome-associated membrane protein 1 (LAMP1) in the cerebellum of Npc1^-/- mice. This LAMP1 form was found on activated microglia, and its appearance correlated both spatially and temporally with cerebellar Purkinje neuron loss. To test the importance of complex asparagine-linked glycosylation in NPC1 pathology, we generated NPC1 knock-out mice deficient in MGAT5, a key Golgi-resident glycosyl transferase involved in complex asparagine-linked glycosylation. Our results show that Mgat5^-/-:Npc1^-/- mice were smaller than Mgat5^+/+:Npc1^-/- mice, and exhibited earlier NPC1 disease onset and reduced lifespan. Western blot and lectin binding analyses of cerebellar extracts confirmed the reduction in complex asparagine-linked glycosylation, and the absence of the hyper-glycosylated LAMP1 previously observed. Western blot analysis of cerebellar extracts demonstrated reduced calbindin staining in Mgat5^-/-:Npc1^-/- mice compared to Mgat5^+/+:Npc1^-/- mutant mice, and immunofluorescent staining of cerebellar sections indicated decreased levels of Purkinje neurons and increased astrogliosis in Mgat5^-/-:Npc1^-/- mice. Our results suggest that reduced asparagine-linked glycosylation increases NPC1 disease severity in mice, and leads to the hypothesis that mutations in genes involved in asparagine-linked glycosylation may contribute to disease severity progression in individuals with NPC1. To examine this with respect to MGAT5, we analyzed 111 NPC1 patients for two MGAT5 SNPs associated with multiple sclerosis; however, we did not identify an association with NPC1 phenotypic severity.

Abnormal LAMP1 glycosylation may play a role in Niemann-Pick disease, type C pathology

A hallmark of Niemann-Pick disease, type C (NPC) is the progressive degeneration of Purkinje neurons in the cerebellum caused by the accumulation of free cholesterol and glycosphingolipids in the lysosome. Recent studies suggest that the state of glycosylation of lysosomal membrane proteins may play a role in disease progression. Our study has identified the presence of a highly glycosylated form of Lysosome Associated Membrane Protein 1 (LAMP1) that correlated spatiotemporally with Purkinje neuron loss. This form of LAMP1 was predominantly localized to activated microglia; showing a ~5-fold increase in surface labeling by FACS analysis. This suggests a potential role for LAMP1 in the neuro-inflammatory process in these mice during disease progression. Analysis of other mouse models of neurodegeneration that exhibit neuro-inflammation showed little or no presence of this glycosylated form of LAMP1, suggesting this observation for LAMP1 is specific to NPC disease. Furthermore, early treatment of Npc1-/- mice with 2-hydroxypropyl-β-cyclodextrin (HPβCD), significantly prevented the appearance of the glycosylated LAMP1 in the cerebellum of Npc1-/- mice at 7 weeks, consistent with the prevention of neuro-inflammation in mice treated with this drug. Treatment of Npc1-/- mice with HPβCD at 7 weeks, after disease onset, did not reverse or prevent further appearance of the hyperglycosylated LAMP1, demonstrating that once this aspect of neuro-inflammation began, it continued despite the HPβCD treatment. Analysis of LAMP1 in cerebellar tissue of NPC1 patients showed a small level of hyperglycosylated LAMP1 in the tissue, however, this was not seen in the CSF of patients.

Abstract 4466: Adenomatous polyposis coli transcriptionally regulates epithelial membrane protein 2 to regulate apical-basal polarity

Adenomatous Polyposis Coli (APC) is a well-known negative regulator of the Wnt pathway; however, it also regulates polarity proteins. Loss of apical-basal polarity disrupts several cellular processes including epithelial structure and intracellular signaling, and is an early marker for tumor development. We previously demonstrated that APC knockdown (APCKD) in Madin-Darby Canine Kidney (MDCK) cells altered cyst size and inverted polarity in 3D culture. Through microarray analysis we made the novel observation that APC loss increased Epithelial Membrane Protein 2 (EMP2) expression. Interestingly, EMP2 knockdown in APCKD cells decreased cyst size and restored apical polarity. These data suggest a previously unknown role for EMP2 in regulating polarity; however, how EMP2 influences APC-mediated polarity remains unknown. Therefore we hypothesize that APC transcriptionally regulates EMP2 to influence apical-basal polarity. In this study, we investigate transcriptional activation of EMP2 using bioinformatics, transcription factor DNA/protein arrays, luciferase reporters, and ChIP assays. EMP2 promoter screens (ConTra v3) identified binding sites for signal transducer and activator of transcription 1 and 3 (STAT1 and 3), and E2F transcription factor 1 (E2F1). Interestingly, APCKD cells exhibited increased expression of STAT1 and E2F1 in DNA/protein arrays compared to controls. Additionally, STAT3 activation was increased in APCKD cells in reporter assays. These studies identified STAT3, STAT1, and E2F1 as possible APC-mediated transcriptional regulators of EMP2. Current studies utilizing luciferase reporter assays aim to determine if E2F1 and STAT1 are transcriptionally active upon APC loss. ChIP assays are being utilized to determine if these candidate transcription factors can bind the canine EMP2 promoter. As CREB is a known transcriptional regulator of EMP2, it was used as a positive control for EMP2 promoter binding. However, no changes in CREB binding are expected between APCKD and MDCK cells, as DNA/protein arrays and luciferase reporter assays did not reveal changes in CREB expression or activity upon APC loss. In preliminary studies, E2F1 was found to weakly bind the canine EMP2 promoter, though this binding was not regulated by APC. Current studies seek to determine if STAT1 and STAT3 bind the EMP2 promoter. Reporter assays using mutant EMP2 promoter constructs are being used to assess if the candidate transcription factors drive EMP2 expression upon APC loss. Future studies will determine if candidate transcription factors influence APC-mediated polarity. Transcription factors will be inhibited in APCKD cells and activated in MDCK cells and EMP2 expression, apical polarity and cyst size will be evaluated in 3D culture. Understanding the interaction of APC and EMP2 and the influence on polarity will identify key players in APC disease progression.

Citation Format: Alyssa Lesko, Carolyn Ahlers, Anna T. Lyons, Jocelyn D. Gaona, Jenifer R. Prosperi. Adenomatous polyposis coli transcriptionally regulates epithelial membrane protein 2 to regulate apical-basal polarity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4466.

Interfacial asparagine residues within an amide tetrad contribute to Max helix-loop-helix leucine zipper homodimer stability

The transcription factor Max is the obligate dimerization partner of the Myc oncoprotein. The pivotal role of Max within the Myc regulatory network is dependent upon its ability to dimerize via the helix-loop-helix leucine zipper domain. The Max homodimer contains a tetrad of polar residues at the interface of the leucine zipper domain. A conserved interfacial Asn residue at an equivalent position in two other leucine zipper proteins has been shown to decrease homodimer stability. The unusual arrangement of this Gln-Asn/Gln'-Asn' tetrad prompted us to investigate whether Asn(92) plays a similar role in destabilizing the Max homodimer. This residue was sequentially replaced with aliphatic and charged residues. Thermal denaturation, redox time course and analytical ultracentrifugation studies show that the N92V mutation does not increase homodimer stability. Replacing this residue with negatively charged side chains in N92D and N92E destabilizes the mutant homodimer. Further replacement of Gln(91) indicated that H bonding between Gln(91) and Asn(92) residues is not significant to the stability of the native protein. These data collectively demonstrate the central role of Asn(92) in homodimer interactions. Molecular modelling studies illustrate the favorable packing of the native Asn residue at the dimer interface compared with that of the mutant Max peptides.