Model Of Human Breast Cancer Research Articles

Integration of an LPAR1 Antagonist into Liposomes Enhances Their Internalization and Tumor Accumulation in an Animal Model of Human Metastatic Breast Cancer.

Lysophosphatidic acid receptor 1 (LPAR1) is elevated in breast cancer. The deregulation of LPAR1, including the function and level of expression, is linked to cancer initiation, progression, and metastasis. LPAR1 antagonists, AM095 or Ki16425, may be effective therapeutic molecules, yet their limited water solubility hinders in vivo delivery. In this study, we report on the synthesis of two liposomal formulations incorporating AM095 or Ki16425, embedded within the lipid bilayer, as targeted nanocarriers for metastatic breast cancer (MBC). The data show that the Ki16425 liposomal formulation exhibited a 50% increase in internalization by MBC mouse epithelial cells (4T1) and a 100% increase in tumor accumulation in a mouse model of MBC compared with that of a blank liposomal formulation (control). At the same time, normal mouse epithelial cells (EpH-4Ev) internalized the Ki16425 liposomal formulation 25% lesser than the control formulation. Molecular dynamics simulations show that the integration of AM095 or Ki16425 modified the physical and mechanical properties of the lipid bilayer, making it more flexible in these liposomal formulations compared with liposomes without drug. The incorporation of an LPAR1 antagonist within a liposomal drug delivery system represents a viable therapeutic approach for targeting the LPA-LPAR1 axis, which may hinder the progression of MBC.

MYC is a clinically significant driver of mTOR inhibitor resistance in breast cancer.

Targeting the PI3K-AKT-mTOR pathway is a promising therapeutic strategy for breast cancer treatment. However, low response rates and development of resistance to PI3K-AKT-mTOR inhibitors remain major clinical challenges. Here, we show that MYC activation drives resistance to mTOR inhibitors (mTORi) in breast cancer. Multiomic profiling of mouse invasive lobular carcinoma (ILC) tumors revealed recurrent Myc amplifications in tumors that acquired resistance to the mTORi AZD8055. MYC activation was associated with biological processes linked to mTORi response and counteracted mTORi-induced translation inhibition by promoting translation of ribosomal proteins. In vitro and in vivo induction of MYC conferred mTORi resistance in mouse and human breast cancer models. Conversely, AZD8055-resistant ILC cells depended on MYC, as demonstrated by the synergistic effects of mTORi and MYCi combination treatment. Notably, MYC status was significantly associated with poor response to everolimus therapy in metastatic breast cancer patients. Thus, MYC is a clinically relevant driver of mTORi resistance that may stratify breast cancer patients for mTOR-targeted therapies.

The second-generation curcumin analogue RL71 elicits G2/M cell cycle arrest and apoptosis in canine osteosarcoma cells.

Canine osteosarcoma is an aggressive cancer, comprising 85% of canine bone neoplasms. Current treatment practices of surgery and chemotherapy increase 1-year survival by only 45%. The curcumin analogue RL71, has demonstrated potent in vitro and in vivo efficacy in several models of human breast cancer through increased apoptosis and cell cycle arrest. Thus, the present study aimed to investigate efficacy of curcumin analogues in two canine osteosarcoma cell lines. Osteosarcoma cell viability was assessed using the sulforhodamine B assay and mechanisms of action were determined by analysing the levels of cell cycle and apoptotic regulatory proteins via Western blotting. Further evidence was obtained using flow cytometry to detect cell cycle distribution and the number of apoptotic cells. RL71 was the most potent curcumin analogue with EC50 values of 0.64 ± 0.04 and 0.38 ± 0.009 μM (n = 3) in D-17 (commercial) and Gracie canine osteosarcoma cells, respectively. RL71 significantly increased the ratio of cleaved-caspase 3 to pro-caspase 3 and the level of apoptotic cells at the 2× and 5× EC50 concentration (p < 0.001, n = 3). Furthermore, at the same concentration, RL71 significantly increased the number of cells in the G2/M phase. In conclusion, RL71 has potent cytotoxic activity in canine osteosarcoma cells triggering G2/M arrest and apoptosis at concentrations achievable in vivo. Future research should further investigate molecular mechanisms for these changes in other canine osteosarcoma cell lines prior to in vivo investigation.

Deciphering Stromal Changes between Metastatic and Non-metastatic Canine Mammary Carcinomas

Cancer-associated stroma (CAS) is widely recognized to influence development and progression of epithelial tumours including breast cancer. Canine mammary tumours (CMTs) such as simple canine mammary carcinomas represent valuable models for human breast cancer also with respect to stromal reprogramming. However, it remains unclear whether and how CAS changes in metastatic tumours compared to non-metastatic ones. To characterize stromal changes between metastatic and non-metastatic CMTs and identify potential drivers of tumour progression, we analysed CAS and matched normal stroma from 16 non-metastatic and 15 metastatic CMTs by RNA-sequencing of microdissected FFPE tissue. We identified 1438 differentially regulated genes between CAS and normal stroma, supporting previous results demonstrating stromal reprogramming in CMTs to be comparable with CAS in human breast cancer and validating deregulation of pathways and genes associated with CAS. Using primary human fibroblasts activated by treatment with TGFβ, we demonstrate some of the strongest expression changes to be conserved in fibroblasts across species. Furthermore, we identify 132 differentially expressed genes between CAS from metastatic and non-metastatic tumours, with strong changes in pathways including chemotaxis, regulation of apoptosis, immune response and TGFβ signalling and validate deregulation of several targets using RT-qPCR. Finally, we identify specific upregulation of COL6A5, F5, GALNT3, CIT and MMP11 in metastatic CAS, suggesting high stromal expression of these targets to be linked to malignancy and metastasis of CMTs. In summary, our data present a resource supporting further research into stromal changes of the mammary gland in relation to metastasis with implications for both canine and human mammary cancer.

Cytotoxic Activity of a Cold Atmospheric Plasma Jet in Relation to a 3D Cell Model of Human Breast Cancer

Cytotoxic Activity of a Cold Atmospheric Plasma Jet in Relation to a 3D Cell Model of Human Breast Cancer

Resistance to mesenchymal reprogramming sustains clonal propagation in metastatic breast cancer

The acquisition of mesenchymal traits is considered a hallmark of breast cancer progression. However, the functional relevance of epithelial-to-mesenchymal transition (EMT) remains controversial and context dependent. Here, we isolate epithelial and mesenchymal populations from human breast cancer metastatic biopsies and assess their functional potential invivo. Strikingly, progressively decreasing epithelial cell adhesion molecule (EPCAM) levels correlate with declining disease propagation. Mechanistically, we find that persistent EPCAM expression marks epithelial clones that resist EMT induction and propagate competitively. In contrast, loss of EPCAM defines clones arrested in a mesenchymal state, with concomitant suppression of tumorigenicity and metastatic potential. This dichotomy results from distinct clonal trajectories impacting global epigenetic programs that are determined by the interplay between human ZEB1 and its target GRHL2. Collectively, our results indicate that susceptibility to irreversible EMT restrains clonal propagation, whereas resistance to mesenchymal reprogramming sustains disease spread in multiple models of human metastatic breast cancer, including patient-derived cells invivo.

In vitro Characterization of a novel murine model of cancerous progression

To evaluate a potentially valuable tool to study cancer progression and metastasis, we characterized a novel murine model composed of a parental oncogene-transformed embryonic fibroblast line and five cell lines isolated from progressively advanced tumors. Lines derived from distant metastases displayed significantly greater rates of motility, invasiveness, and extracellular acidification than lines derived from a primary tumor or local metastases. A comprehensive proteomic analysis of these cells showed numerous oncogenes to be upregulated and tumor suppressors to be downregulated in the advanced lines, and provided novel targets for future examination. The first cell line capable of extravasation displayed particularly high proteomic variation, which could provide insight into its epithelial to mesenchymal transition. The proteomic variation was less than that of an established human breast cancer model, indicating that the observed differences are more likely contributive to tumorigenesis. In total, we validated a novel cell model for the study of tumorigenesis, while providing a robust proteomic data set to guide future research.

Abstract 4089: PanCAR-specific antibody-cytokine fusion proteins

Abstract CAR-T cells are a potent immunotherapy that redirect T cell specificity towards cell surface tumor-associated antigens. While this therapy has been effective in hematological malignancies, therapies against solid tumors not achieved the same efficacy due to a multitude of additional challenges, including a lack of tumor specific antigens and an immunosuppressive tumor microenvironment. One strategy to increase T cell potency is to use fourth generation CAR-T cells that also secrete an immunostimulatory factor, such as a cytokine. We have created CAR-T cells targeting Tn-MUC1 utilizing a scFv from the 5E5 antibody that also secrete interleukin-12 (IL-12), interleukin-18 (IL-18), and interleukin-23 (IL-23). These cytokine-secreting CAR-T cells have shown an increase in efficacy against multiple epithelial based tumors in impedance-based killing assays. In a xenograft model of human breast cancer, CAR-T cells secreting IL-12 and IL-23 were able to significantly delay tumor growth compared to non-transduced T cells, CAR-T cells alone, and CAR-T cells secreting IL-18. While these cells showed good efficacy in vivo, clinical translation is difficult due to concerns over cytokine storm due to the constitutive secretion of cytokines. To overcome this, we created a fusion protein utilizing an antibody specific to an invariant region found in majority of CAR molecules, including those utilized commercially available therapies and under pre-clinical development, fused to the three immunostimulatory cytokines. In impedance-based killing assays, antibody-cytokine fusions stimulated non-cytokine secreting CAR-T cells to completely clear the tumor at an E:T ratio in which the CAR-T cells incubated with only the antibody alone were unable to control the tumor growth. Interestingly, combination therapy of CAR-T cells and antibody-cytokine fusions outperformed CAR-T cells constitutively secreting the same cytokines in in vitro assays. This work highlights the use of a single reagent capable of increasing the efficacy of the majority of CAR-T cell therapies and may be an important contribution towards treating solid tumor malignancies with CAR-T cell therapies. Citation Format: John T. Keane, Avery D. Posey. PanCAR-specific antibody-cytokine fusion proteins. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4089.

Abstract 2938: Preclinical development of a novel bispecific mAb-Trap fusion protein, IMM2902, targeting both HER2 and CD47 as cancer immunotherapy

Abstract The overexpression of human epidermal growth factor receptor 2 (HER2) has been identified in a variety of solid tumors including breast cancer (BC), gastric cancer and is associated with tumor recurrence, brain metastasis, and an overall poor prognosis. As such, HER2 has become a major target in the research and development of anticancer drugs. CD47, an integrin-associated protein, is expressed in many human cancer cells, especially upregulated preferentially in HER2-expressing cells. Co-expression of HER2 and CD47 is more frequently detected in recurrent BC patients with poor prognosis when comparing with the counterpart primary tumors. IMM2902 is a first-in-class, clinical-stage, novel recombinant bispecific mAb-Trap fusion protein targeting both CD47 and HER2 simultaneously. The binding activities of IMM2902, measured as EC50, to total CD47+ and HER2+ in BT474, NCI-N87 and SKOV-3 cancer cell lines are 16, 11 and 5 nM respectively. The affinity of IMM2902 to HER2 is about 15 times higher than that of CD47. IMM2902 not only prevents the engagement of CD47 with SIRPα and hence blocks “don’t eat me” signal of CD47/SIRPα, but also induces strong antibody-dependent cell-mediated cytotoxicity (ADCC, EC50 = 0.0045 - 0.0544 nM) and antibody-dependent cellular phagocytosis (ADCP, EC50 = 0.05 - 0.13 nM) activity with specifically engineered IgG1 Fc fragment. Most importantly, IMM2902 induces accelerated HER2 degradation in tumor tissues. Despite its high affinity to CD47, IMM2902 does not binds to CD47 on erythrocyte membrane, therefore, unlike conventional CD47 mAb, IMM2902 demonstrated a minimal impact on red blood cells (RBC). In preclinical research, IMM2902 has demonstrated a much stronger antitumor activity with excellent tolerability in a mouse model of human breast cancer (dose range 3.5 - 10 mg/kg) and a mouse model of human gastric cancer (dose range 1 -18 mg/kg) than that of trastuzumab (targeting HER2 only) alone, IMM01 (a SIRPα-Fc fusion protein) alone, and the combination of trastuzumab and IMM01. In HER2-low SUN-1 xenograft models, IMM2902 has showed a strong tumor growth inhibition at doses between 2 to 18 mg/kg. Intriguingly, IMM2902 also has exhibited potent tumor killing activity against breast cancer resistant to trastuzumab (HCC-1954 and patient-derived xenografts herceptin-resistant model) at doses between 3.5 to 10 mg/kg. Given the strong preclinical antitumor activity as well as the favorable safety profile, IMM2902 may serve as a potent immunotherapy for HER2-expressing cancers via dual blockade of CD47 and HER2. A Phase 1 clinical trial exploring safety, tolerability, and preliminary efficacy of IMM2902 in patients with HER2-expressing advanced solid tumors is currently ongoing in both China (CXSL2101035) and USA (NCT05076591). Citation Format: Binglei Zhang, Song Li, Dianze Chen, Dandan Liu, Huiqin Guo, Chunmei Yang, Li Zhang, Wei Zhang, Xiaoping Tu, Liang Peng, Gui Zhao, Ruliang Zhang, Frank X. Gan, Wenzhi Tian, Fan Zhang, Yongping Song. Preclinical development of a novel bispecific mAb-Trap fusion protein, IMM2902, targeting both HER2 and CD47 as cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2938.

Сравнение онколитической активности рекомбинантных штаммов вируса осповакцины LIVP-RFP и MVA-RFP в отношении солидных опухолей

Among oncolytic viruses, modified vaccinia virus Ankara (MVA), a highly attenuated vaccinia virus (VV) is a well-studied variant with promising results in preclinical and clinical trials. The Lister VV strain from the Moscow Institute of Viral Preparations (LIVP) has been studied to a lesser extent than MVA and has a different oncolytic property from MVA. The aim of this work was to compare the oncolytic efficacy of LIVP and MVA strains against solid tumors. We developed recombinant variants LIVP-RFP and MVA-RFP; to enhance onco-selectivity thymidine kinase (TK) gene was inactivated by insertion of red fluorescent protein (RFP) gene to the TK locus. The replication kinetics and oncolytic activity of the obtained recombinant strains were evaluated in vitro and in vivo on tumor cell lines and mouse syngeneic tumor models of metastatic mouse 4T1 mammary adenocarcinoma, CT26 colon adenocarcinoma, and B16 melanoma. Both MVA-RFP and LIVP-RFP showed high replication efficiency in tumor cells and pronounced oncolytic activity against B16 melanoma and 4T1 breast adenocarcinoma allografts. In relation to 4T1, which is a model of triple negative human breast cancer, LIVP-RFP showed more than 50% increased cytotoxicity in in vitro tests compared to MVA-RFP, as well as a significant slowdown in the progression of 4T1 allografts and an increase in animal survival in experiments in vivo. Thus, the LIVP strain may be more promising than MVA as a platform for the development of recombinant oncolytic viruses for the breast cancer treatment.

HED, a Human-Engineered Domain, Confers a Unique Fc-Binding Activity to Produce a New Class of Humanized Antibody-like Molecules.

Our laboratory has identified and developed a unique human-engineered domain (HED) structure that was obtained from the human Alpha-2-macroglobulin receptor-associated protein based on the three-dimensional structure of the Z-domain derived from Staphylococcal protein A. This HED retains µM binding activity to the human IgG1CH2-CH3 elbow region. We determined the crystal structure of HED in association with IgG1's Fc. This demonstrated that HED preserves the same three-bundle helix structure and Fc-interacting residues as the Z domain. HED was fused to the single chain variable fragment (scFv) of mAb 4D5 to produce an antibody-like protein capable of interacting with the p185Her2/neu ectodomain and the Fc of IgG. When further fused with murine IFN-γ (mIFN-γ) at the carboxy terminus, the novel species exhibited antitumor efficacy in vivo in a mouse model of human breast cancer. The HED is a novel platform for the therapeutic utilization of engineered proteins to alleviate human disease.

Discovery of a Potent and Selective CCR8 Small Molecular Antagonist IPG7236 for the Treatment of Cancer.

Recently, there has been increasing evidence indicating that the CC chemokine receptor 8 (CCR8) plays an important role in mediating the recruitment and immunosuppressive function of regulatory T (Treg) cells in the tumor microenvironment. Therefore, the development of a specific CCR8 antagonist presents a potential therapeutic strategy against cancer. Despite a few small molecules having been reported as CCR8 antagonists, none has progressed to the clinical stage. Herein, we described a potent and selective CCR8 antagonist (compound 1, IPG7236) as the first small molecule to advance to the clinical stage. IPG7236 demonstrated an anti-cancer effect via modulating Treg and cytotoxic T (CD8+ T) cells. IPG7236 alone or in combination with PD-1 antibody exhibited significant tumor suppression effects in the mouse xenograft model of human breast cancer. IPG7236 is a promising clinical candidate that targets CCR8 with excellent in vitro ADMET properties, pharmacokinetics, safety profiles, and in vivo efficacy.

Involvement of protumor macrophages in breast cancer progression and characterization of macrophage phenotypes.

Tumor-associated macrophages (TAMs) are the most prominent immune cells in the breast cancer microenvironment, and the protumor functions of TAMs are thought to affect cancer progression and resistance to anticancer therapy. Numerous studies using human breast cancer samples, cell lines, and murine breast cancer models have revealed details of the mechanisms by which the protumor functions of TAMs are activated. Recent advances have highlighted the significant involvement of TAMs in the resistance of breast cancer cells to immunotherapy. Tumor-associated macrophages express a number of immunosuppressive genes, and single-cell sequence analyses of human and murine cancer samples have helped elucidate the mechanism of TAM-induced immunosuppression. As TAMs are considered suitable targets for anticancer therapies, we summarized the protumor functions of TAMs and the potential of anticancer therapies targeting TAMs, with a focus on breast cancer research.

Abstract P3-08-02: Prospective Use of Feline Mammary Carcinomas to Study MiR-10b and Metastasis

Abstract Despite many advances in cancer treatment, metastatic disease is estimated to be responsible for 90% of all cancer-related deaths. Current treatments for metastatic disease target various aspects of carcinogenesis but not specifically the metastatic process, representing a major unmet clinical need. MicroRNA-10b, a small non-coding RNA, offers tremendous potential as a treatment target for metastatic disease. It is implicated in invasion, migration, and viability of metastatic cells across a variety of cancer types, and it is upregulated in metastases compared to their matched primary tumor, establishing miR-10b as a potential treatment target unique to metastatic niche. We have previously developed a therapeutic targeting miR-10b in metastases and tested it in murine models of metastatic breast cancer. This therapeutic, consisting of an anti-miR-10b antisense oligonucleotide conjugated to iron oxide-based nanoparticles, prevents metastasis and eradicates pre-existing metastases in murine breast cancer models. With an outlook to clinical translation of our approach, we seek to test our therapeutic strategy in larger animal models. Feline mammary carcinomas are considered by most to be the best large animal model for human breast cancer due to similarities such as relative age of onset, histopathology, metastatic patterns, and treatment response. To support the use of this model with our therapeutic, we investigated the characteristics of miR-10b expression in spontaneous metastatic breast cancer in companion cats. Archival blocks of matched primary tumors and metastatic lymph nodes from companion cats diagnosed with mammary carcinoma (n=9, 44%TNBC, 56%HER2+) were obtained from the tissue bank of the Michigan State University (MSU) Veterinary Diagnostic Laboratory (VDL). Tissues were analyzed for miR-10b and its target HOXD10 expression using qRT-PCR and in situ hybridization. qRT-PCR revealed that miR-10b expression was significantly upregulated in 55.5% of lymph node metastases compared to their matched primary tumor, mirroring findings in human metastatic cancer. This was validated by qRT-PCR for HOXD10 gene expression (a direct target of miR-10b), which was significantly downregulated in these metastases compared to their matched primary tumor. In situ hybridization demonstrated that miR-10b expression was increased at the invasive edge of tumors and in actively invading cells, suggesting miR-10b plays a similar role in invasion in feline breast cancer as it does in human breast cancer. Altogether, these findings support the use of feline mammary carcinomas as a model of human breast cancer and as an excellent candidate for treatment with our therapeutic. Citation Format: Alan Halim, N. Anna Savan, Paulo Vilar Saavedra, Vilma Yuzbasiyan-Gurkan, Matti Kiupel, Lorenzo Sempere, Anna Moore. Prospective Use of Feline Mammary Carcinomas to Study MiR-10b and Metastasis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-08-02.

Abstract P6-14-05: Regulation of cellular identity and spatial organization during collective breast cancer invasion

Abstract An early step in breast cancer progression is invasion of tumor cells into surrounding tissues. In many breast cancers, particularly ductal carcinomas, this invasion is accomplished by tumor cells migrating as a cohesive group. This often involves cells that take on heterogeneous roles as either leader or follower cells. While studies in common mouse and human breast cancer models have established that leader cells express high levels of keratin-14 (K14) and other basal epithelial markers, the molecular mechanisms regulating K14+ leader cell identity remain obscure. Here we performed time-sampled single cell RNA-sequencing in 3D type I collagen-embedded tumor organoids isolated from the MMTV-PyMT luminal B model of breast cancer. 11 distinct cellular transcriptional states were identified and correlated with K14 expression and invasive strand formation. Having identified the leader cell state we next asked what transcription factors were enriched, reasoning that transcription factors could be master regulators of leader cell fate. 30 different shRNAs targeting 10 genes were systematically evaluated for their effects on collective invasion. From this screen, suppression of Hes1, the downstream target of Notch signaling, yielded a marked switch from collective to single cell invasion. Disseminating single tumor cells maintained high expression of K14 in Hes1 knockdown organoids which was phenocopied by gamma-secretase inhibition in a human TNBC PDX model. Because K14+ tumor cells highly express the Notch ligand Jag1, these results support a model in which Notch signaling, specifically through activation of Hes1, dictates leader cell identity and spatial organization during collective invasion. Studies are ongoing investigating the impact of Hes1 dynamics on leader cell adhesion, hybrid EMT state, and preference for single versus collective metastasis. Because Notch suppression induces leader cell dissemination, we propose that Notch targeted therapy should be combined with therapies eradicating leader cells. Citation Format: Andrea E. Doak, Kevin J. Cheung. Regulation of cellular identity and spatial organization during collective breast cancer invasion. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-14-05.

MTOR pathway as a potential therapeutic target for cancer stem cells in canine mammary carcinoma.

Mammary adenocarcinoma, the most common cancer in female dogs, often exhibits the lymph node and lung metastases and has a higher mortality rate. However, mammary adenocarcinoma has no established treatment, except early surgical excision. Canine mammary carcinoma has many common features with human mammary carcinoma, including clinical characteristics, heterogeneity, and genetic aberrations, making it an excellent spontaneous tumor model for human breast cancer. Diverse cancers comprised heterogeneous cell populations originating from cancer stem cells (CSCs) with self-renewal ability. Therefore, in addition to conventional therapy, therapeutic strategies targeting CSCs are essential for cancer eradication. The present study aimed to extract inhibitors of canine mammary CSCs that suppress their self-renewal ability. Sphere-formation assay, which evaluates self-renewal ability, was performed for the canine mammary cancer cell lines CTBp and CNMp. The spheres formed in this assay were used in inhibitor library screening, which identified various signaling pathways such as proteosome, stress inducer, and mammalian target of rapamycin (mTOR). The present study focused on the mTOR signaling pathway. Western blotting showed higher levels of phosphorylated mTOR in sphere-forming CTBp and CNMp cells than in adherent cells. Drug sensitivity examination using the mTOR inhibitors everolimus and temsirolimus revealed dose-dependent reductions in viability among both sphere-forming cells and adherent cells. Expression of phosphorylated mTOR in adherent and sphere-forming cells decreased by everolimus and temsirolimus treatment. In mice transplanted with CTBp-derived spheres, everolimus treatment significantly decreased tumor volume compared to control. These results reveal that the mTOR signaling pathway may be a potential to be a therapeutic target in both cancer cells and CSCs. Novel therapeutic strategies for canine mammary carcinoma are expected to benefit to human breast carcinoma as well.

Abstract A014: Transcriptional regulation of basal leader cell identity during collective breast cancer invasion

Abstract An early step in breast cancer progression is invasion of tumor cells into surrounding tissues. In many breast cancers, particularly ductal carcinomas, this invasion is accomplished by tumor cells migrating as a cohesive group. This often involves cells that take on heterogeneous roles as either leader or follower cells. Studies in common mouse and human breast cancer models have established that leader cells express high levels of keratin-14 (K14) and other basal epithelial markers. The presence of these K14+ cells promote metastasis and predict poor prognosis. The molecular mechanisms regulating K14+ leader cell identity and the methods for targeted depletion of these cells remain obscure. Here we performed time-sampled single cell RNA-sequencing in 3D type I collagen-embedded tumor organoids isolated from the MMTV-PyMT luminal B model of breast cancer. 11 distinct cellular transcriptional states were identified, and through correlation with K14 expression and invasive strand formation we classified one of the states as leader cells. Having confirmed the leader cell cluster markers spatially localize to the invasive front, we next asked which transcription factors were enriched, reasoning that transcription factors could be master regulators of leader cell fate. Three different shRNAs targeting ten genes were systematically evaluated for their effects on collective invasion and keratin-14 transcription. Each transcription factor was designated as either an invasion promoter or invasion suppressor depending on the correlation between transcription factor expression and organoid invasion. Studies are ongoing investigating the impact of invasion-promoting and invasion-suppressing transcription factors on cellular transcriptional states and metastatic dissemination in-vivo. We propose that targeting invasion-suppressing pathways could be combined with therapies that specifically target and eliminate K14+ invasive cells. To this end, we have identified multiple candidate druggable targets and specific surface markers expressed in K14+ invasive cells. Citation Format: Andrea E. Doak, Rose Qu, Kevin J. Cheung. Transcriptional regulation of basal leader cell identity during collective breast cancer invasion [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A014.

Comparison of Characterization in Two-Dimensional and Three-Dimensional Canine Mammary Gland Tumor Cell Models.

Canine mammary gland tumors can be used as predictive models for human breast cancer. There are several types of microRNAs common in human breast cancer and canine mammary gland tumors. The functions of microRNAs in canine mammary gland tumors are not well understood. We compared the characterization of microRNA expression in two-dimensional and three-dimensional canine mammary gland tumor cell models. We evaluated the differences between two- and three-dimensional cultured canine mammary gland tumor SNP cells by assessing microRNA expression levels, morphology, drug sensitivity, and hypoxia. The expression of microRNA-210 in the three-dimensional-SNP cells was 10.19 times higher than that in the two-dimensional-SNP cells. The intracellular concentrations of doxorubicin in the two- and three-dimensional-SNP cells were 0.330 ± 0.013 and 0.290 ± 0.048 nM/mg protein, respectively. The IC50 values of doxorubicin for the two- and three-dimensional-SNP cells were 5.2 and 1.6 μM, respectively. Fluorescence of the hypoxia probe, LOX-1, was observed inside the sphere of three-dimensional-SNP cells without echinomycin but not in two-dimensional-SNP cells. The three-dimensional-SNP cells treated with echinomycin showed weak LOX-1 fluorescence. The present study showed a clear difference in microRNA expression levels in cells cultured in a two-dimensional adherent versus a three-dimensional spheroid model.

Transcriptomic changes underlying EGFR inhibitor resistance in human and mouse models of basal-like breast cancer.

The goals of this study were to identify transcriptomic changes that arise in basal-like breast cancer cells during the development of resistance to epidermal growth factor receptor inhibitors (EGFRi) and to identify drugs that are cytotoxic once EGFRi resistance occurs. Human patient-derived xenografts (PDXs) were grown in immunodeficient mice and treated with a set of EGFRi; the EGFRi erlotinib was selected for more expansive in vivo studies. Single-cell RNA sequencing was performed on mammary tumors from the basal-like PDX WHIM2 that was treated with vehicle or erlotinib for 9weeks. The PDX was then subjected to long-term erlotinib treatment in vivo. Through serial passaging, an erlotinib-resistant subline of WHIM2 was generated. Bulk RNA-sequencing was performed on parental and erlotinib-resistant tumors. In vitro high-throughput drug screening with > 500 clinically used compounds was performed on parental and erlotinib-resistant cells. Previously published bulk gene expression microarray data from MMTV-Wnt1 tumors were contrasted with the WHIM2 PDX data. Erlotinib effectively inhibited WHIM2 tumor growth for approximately 4weeks. Compared to untreated cells, single-cell RNA sequencing revealed that a greater proportion of erlotinib-treated cells were in the G1 phase of the cell cycle. Comparison of WHIM2 and MMTV-Wnt1 gene expression data revealed a set of 38 overlapping genes that were differentially expressed in the erlotinib-resistant WHIM2 and MMTV-Wnt1 tumors. Comparison of all three data types revealed five genes that were upregulated across all erlotinib-resistant samples: IL19, KLK7, LCN2, SAA1, and SAA2. Of these five genes, LCN2 was most abundantly expressed in triple-negative breast cancers, and its knockdown restored erlotinib sensitivity in vitro. Despite transcriptomic differences, parental and erlotinib-resistant WHIM2 displayed similar responses to the majority of drugs assessed for cytotoxicity in vitro. This study identified transcriptomic changes arising in erlotinib-resistant basal-like breast cancer. These data could be used to identify a biomarker or develop a gene signature predictive of patient response to EGFRi. Future studies should explore the predictive capacity of these gene signatures as well as how LCN2 contributes to the development of EGFRi resistance.

Abstract A009: ZMYND8 is an epigenetic regulator of 27-hydroxycholesterol that promotes tumorigenicity of breast cancer stem cells

Abstract 27-hydroxycholesterol (27-HC) is the most abundant oxysterol that increases the risk of breast cancer progression. However, little is known about epigenetic regulation of 27-HC metabolism and its role in breast tumor initiation. Using genetic mouse mammary tumor and human breast cancer models, we showed here that the histone reader ZMYND8 was selectively expressed in breast cancer stem cells (BCSCs) and promoted epithelial-mesenchymal transition (EMT), BCSC maintenance and self-renewal, and oncogenic transformation through its epigenetic functions, leading to breast tumor initiation. Mechanistically, ZMYND8 was a master transcriptional regulator of 27-HC metabolism. It increased cholesterol biosynthesis and oxidation but blocked cholesterol efflux and 27-HC catabolism leading to accumulation of 27-HC in BCSCs. Consequently, 27-HC promoted EMT, oncogenic transformation, and tumor initiation through activation of liver X receptor. These findings reveal that ZMYND8 is an epigenetic booster that drives breast tumor initiation through metabolic reprogramming. Citation Format: Weibo Luo, Maowu Luo. ZMYND8 is an epigenetic regulator of 27-hydroxycholesterol that promotes tumorigenicity of breast cancer stem cells. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr A009.