Protein Phosphatase 1H, Cyclin-Dependent Kinase Inhibitor p27, and Cyclin-Dependent Kinase 2 in Paclitaxel Resistance for Triple Negative Breast Cancers

Purpose

Paclitaxel is a cytotoxic chemotherapy commonly used in patients with triple negative breast cancer (TNBC); however, the resistance to paclitaxel is a cause of poor response in the patients. The aim of this study was to examine the role of protein phosphatase 1H (PPM1H) in paclitaxel resistance in breast cancer patients.

Methods

To investigate the function of PPM1H in paclitaxel treatment, we conducted in vitro assays and molecular experiments using a stable cell line (MDA-MB-231) in which PPM1H is overexpressed. We also performed molecular analyses on patient tissue samples. Molecular expression related to PPM1H in breast cancer patients was analyzed using TCGA data.

Results

We investigated whether PPM1H was associated with paclitaxel resistance in breast cancer. PPM1H expression was upregulated in breast cancer cells treated with paclitaxel. We also observed that overexpression of PPM1H in breast cancer cells resulted in increased sensitivity to paclitaxel in vitro. Additionally, paclitaxel treatment induced dephosphorylation of cyclin-dependent kinase (CDK) inhibitor p27 (p27), which was more evident in PPM1H-overexpressing cells. To understand how upregulation of PPM1H increases paclitaxel sensitivity, we determined the levels of p27, phospho-p27, and CDK2, since CDK2 exerts antagonistic effects against PPM1H on p27 phosphorylation. The patient-derived xenograft (PDX) tumors that did not respond to paclitaxel showed increased levels of CDK2 and phospho-p27 and decreased levels of total p27 compared to the other breast tumor tissues. The use of dinaciclib, a selective CDK inhibitor, significantly inhibited tumor growth in the PDX model.

Conclusion

CDK2 kinase activity was significantly upregulated in basal breast cancer tumors and was negatively correlated with p27 protein levels in the TCGA breast cancer dataset, suggesting that targeting CDK2 may be an effective treatment strategy for TNBC patients.

AKR1C2 Promotes Metastasis and Regulates the Molecular Features of Luminal Androgen Receptor Subtype in Triple Negative Breast Cancer Cells

PURPOSE

Patients with triple-negative breast cancer (TNBC) have an increased risk of distant metastasis compared to those with other subtypes. In this study, we aimed to identify the genes associated with distant metastasis in TNBC and their underlying mechanisms.

METHODS

We established patient-derived xenograft (PDX) models using surgically resected breast cancer tissues from 31 patients with TNBC. Among these, 15 patients subsequently developed distant metastases. Candidate metastasis-associated genes were identified using RNA sequencing. In vitro wound healing, proliferation, migration, and invasion assays and in vivo tumor xenograft and metastasis assays were performed to determine the functional importance of aldo-keto reductase family 1 member C2 (AKR1C2). Additionally, we used the METABRIC dataset to investigate the potential role of AKR1C2 in regulating TNBC subtypes and their downstream signaling activities.

RESULTS

RNA sequencing of primary and PDX tumors showed that genes involved in steroid hormone biosynthesis, including AKR1C2, were significantly upregulated in patients who subsequently developed metastasis. In vitro and in vivo assays showed that silencing of AKR1C2 resulted in reduced cell proliferation, migration, invasion, tumor growth, and incidence of lung metastasis. AKR1C2 was upregulated in the luminal androgen receptor (LAR) subtype of TNBC in the METABRIC dataset, and AKR1C2 silencing resulted in the downregulation of LAR classifier genes in TNBC cell lines. The androgen receptor (AR) gene was a downstream mediator of AKR1C2-associated phenotypes in TNBC cells. AKR1C2 expression was associated with gene expression pathways that regulate AR expression, including JAK-STAT signaling or interleukin 6 (IL-6). The levels of phospho-signal transducer and activator of transcription and IL-6, along with secreted IL-6, were significantly downregulated in AKR1C2-silenced TNBC cells.

CONCLUSION

Our data indicate that AKR1C2 is an important regulator of cancer growth and metastasis in TNBC and may be a critical determinant of LAR subtype features.

STIM1 knock-down decreases the affinity of obinutuzumab for CD20 by altering CD20 localization to Triton-soluble membrane

Obinutuzumab is thought to exert its effects through its high antibody-dependent cellular cytotoxicity (ADCC) via glyco-engineering of the Fc region. In addition, obinutuzumab causes direct binding-induced cell death (DCD) only by specifically binding to its target CD20, a Ca²⁺ channel. However, the specific features of CD20 related to obinutuzumab binding-induction of cell death are not clearly understood. In this study, we evaluated the relationship between the Ca²⁺ channel features of CD20 as a store-operated Ca²⁺ channel (SOC) and obinutuzumab binding-induced cell death. Ca²⁺ channel function and biochemical analysis revealed that CD20 is an Orai1- and stromal interaction molecule (STIM1)-dependent Ca²⁺ pore. However, binding of obinutuzumab on CD20 did not have any effect on Ca²⁺ influx activity of CD20; the direct cell death rate mediated by obinutuzumab binding was almost equivalent with or without the extracellular Ca²⁺ condition. Given the apparent interaction between STIM1 and CD20, we observed Triton-X solubilized obinutuzumab-bound CD20 accompanied by STIM1. Subsequently, obinutuzumab binding and cell death were decreased by STIM1 knock-down in Ramos B cells. Thus, STIM1 directly contributes to cell death by increasing the affinity of cells for obinutuzumab by transferring CD20 to the Triton-soluble membrane region.

Abstract P2-06-01: Molecular characterization of human malignant phyllodes tumors reveals potential targeted approaches

Malignant phyllodes tumor (MPT) which belong to the fibroepithelial neoplasm spectrum is a rare type of breast malignancy, and currently there is no effective targeted approach available for MPT. In this study, we tried to identify key genomic alterations and biologic pathways in MPT by whole exome and RNA sequencing of nine MPT tissues. Whole exome sequencing revealed somatic alterations in EGFR, MED12, PIK3CA, PIK3R1, PDGFRA, PDGFRB, PTEN, and TP53. Transcriptome sequencing showed dysregulation of ECM-receptor interaction, focal adhesion, and PI3K-Akt signaling in MPTs when compared to normal breast or invasive breast cancer tissues. Based on the transcriptome profiles, the MPTs were classified into two subtypes; fibrous subtype with upregulation of stromal genes such as collagens and epithelial subtype with upregulation of E-cadherin and Claudins. The molecular classification of fibrous and epithelial subtypes was validated in 28 paraffin-embedded MPT tissues. The fibrous subtype showed higher mitotic index and increased risk for recurrence when compared to the epithelial subtype. We established a patient-derived xenograft model from one fibrous subtype MPT which harbored somatic mutation in PIK3R1 and PDGFRB. In that model, targeted treatment against PIK3CA/mTOR and PDGFR pathways effectively suppressed the tumor growth in vivo. Our data provide insights on the biologic understanding of MPT and suggest a clinically relevant molecular classification. Furthermore, we show that developing effective targeted approaches in MPT can be possible with genomic profiles and patient-derived xenograft models. The clinical efficacy of targeting PDGFR and PIK3CA/mTOR pathways in MPT should be tested in future clinical trials.

Citation Format: Moon H-G, Yun J, Hong BS, Lee E, Lee H-B, Han W, Kim J-I, Noh D-Y, Heo W, Hur S, Kang W, Lee C. Molecular characterization of human malignant phyllodes tumors reveals potential targeted approaches [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-06-01.

Abstract PD15-02: Cx3cl1-cx3cr1 axis in liver metastasis of triple negative breast cancer

Triple negative breast cancer (TNBC) is a breast cancer subtype with increased risk of distant metastasis, especially to visceral organs. However, the detailed molecular mechanism underlying the visceral metastasis of TNBC is unknown. We used three patient-derived xenograft models derived from TNBC tumors with different metastatic capacities. PDX1 and PDX2 model developed distant metastasis in only lung and liver, respectively. In contrast, PDX3 tumor metastasized to both lung and liver. RNA sequencing of the primary tumor and distant metastatic sites of these three PDX models was performed. The gene expression profiles of the primary tumors of the three models showed minimally overlapping genes. However, the microenvironment gene expression profiles, measured by using the sequencing reads aligned to mouse genome, showed distinct difference between the models. Among the differentially expressed genes, we identified Cx3cr1 as a significantly upregulated gene in the liver microenvironment of the PDX models that metastasized to liver. Next, we used 4T1 syngeneic mouse mammary carcinoma model to validate the Cx3cr1 in the mouse liver tissues. Interestingly, the Cx3cr1 up-regulation occurred during the pre-metastatic period, and Cx3cl1, the ligand of the Cx3cr1, was also up-regulated in the liver tissue prior to the development of metastasis suggesting the Cx3cr1 regulates the formation of pre-metastatic niche. Cx3cl1, the ligand of the Cx3cr1, was also up-regulated in the liver tissue prior to the development of metastasis. These data suggest that Cx3cl1 and Cx3cr1-mediated tumor-microenvironment interaction is critical in developing liver metastasis in TNBC. Cx3cl1 increased the invasion and migration of Raw264.7 monocyte/macrophage cells and this effect was abrogated by the Cx3cr1 silencing in Raw264.7 cells or treating Cx3cl1 neutralizing antibody. Pathway analysis of the RNA sequencing data showed that genes involved in extracellular matrix remodeling was significantly dysregulated in the liver tissues including Lysyl Oxidase (Lox). Cx3cl1 treatment in Raw264.7 cells resulted in increased expression of Lox and MMP9 mRNA in three-dimensional culture system. The Raw264.7 cells caused increased invasion of 4T1 cells in vitro. In conclusion, our data suggest that Cx3cl1-Cx3cr1 axis plays critical role during the liver metastasis of TNBC.

Citation Format: Woohang Heo, Hye-Youn Son, Ju hee Kim, Kyu Jin Lee, Myeonghee Jeon, Songbin Li, Jeehee Jang, Dong-Young Noh, Wonsik Han, Hyeong-Gon Moon. Cx3cl1-cx3cr1 axis in liver metastasis of triple negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD15-02.

Triple-negative breast cancer-derived extracellular vesicles promote a hepatic pre-metastatic niche via a cascade of microenvironment remodeling

Triple negative breast cancer (TNBC) patients often develop metastases in visceral organs including the liver but the detailed molecular mechanisms of TNBC liver metastasis is not clearly understood. In this study, we tried to dissect the process of pre-metastatic niche formation in liver by using patient-derived xenograft (PDX) models of TNBC with different metastatic propensity. RNA sequencing of TNBC PDX models that successfully metastasized to liver showed up-regulation of Cx3cr1 gene in the liver microenvironment. In syngeneic breast cancer models, the Cx3cr1 up-regulation in liver preceded the development of cancer cell metastasis and was the results of recruitment of CX3CR1-expressing macrophages. The recruitment was induced by the CX3CL1 production from the liver endothelial cells and this CX3CL1-CX3CR1 signaling in the pre-metastatic niche resulted in up-regulation of MMP9 that promoted macrophage migration and cancer cell invasion. Additionally, our data suggest that the extra-cellular vesicles derived from the breast cancer cells induced the TNF-alpha expression in liver which leads to the CX3CL1 up-regulation. Lastly, the plasma CX3CL1 levels in 155 breast cancer patients were significantly associated with development of liver metastasis. Implications: Our data provides previously unknown cascades regarding the molecular education of pre-metastatic niche in liver for TNBC.

Potential Perturbations of Critical Cancer-regulatory Genes in Triple-Negative Breast Cancer Cells Within the Humanized Microenvironment of Patient-derived Xenograft Models

PURPOSE

In this study, we aimed to establish humanized patient-derived xenograft (PDX) models for triple-negative breast cancer (TNBC) using cord blood (CB) hematopoietic stem cells (HSCs). Additionally, we attempted to characterize the immune microenvironment of the humanized PDX model to understand the potential implications of altered tumor-immune interactions in the humanized PDX model on the behavior of TNBC cells.

METHODS

To establish a humanized mouse model, high-purity CD34+ HSCs from CB were transplanted into immunodeficient NOD scid γ mice. Peripheral and intratumoral immune cell compositions of humanized and non-humanized mice were compared. Additionally, RNA sequencing of the tumor tissues was performed to characterize the gene expression features associated with humanization.

RESULTS

After transplanting the CD34+ HSCs, CD45+ human immune cells appeared within five weeks. A humanized mouse model showed viable human immune cells in the peripheral blood, lymphoid organs, and in the tumor microenvironment. Humanized TNBC PDX models showed varying rates of tumor growth compared to that of non-humanized mice. RNA sequencing of the tumor tissue showed significant alterations in tumor tissues from the humanized models. tumor necrosis factor receptor superfamily member 11B (TNFRSF11B) is a shared downregulated gene in tumor tissues from humanized models. Silencing of TNFRSF11B in TNBC cell lines significantly reduced cell proliferation, migration, and invasion in vitro. Additionally, TNFRSF11B silenced cells showed decreased tumorigenicity and metastatic capacity in vivo.

CONCLUSION

Humanized PDX models successfully recreated tumor-immune interactions in TNBC. TNFRSF11B, a commonly downregulated gene in humanized PDX models, may play a key role in tumor growth and metastasis. Differential tumor growth rates and gene expression patterns highlighted the complexities of the immune response in the tumor microenvironment of humanized PDX models.

An integrative approach for exploring the nature of fibroepithelial neoplasms

BACKGROUND

Malignant phyllodes tumour (MPT) is a rare breast malignancy with epithelial and mesenchymal features. Currently, there are no appropriate research models or effective targeted therapeutic approaches for MPT.

METHODS

We collected fresh frozen tissues from nine patients with MPT and performed whole-exome and RNA sequencing. Additionally, we established patient-derived xenograft (PDX) models from patients with MPT and tested the efficacy of targeting dysregulated pathways in MPT using the PDX model from one MPT.

RESULTS

MPT has unique molecular characteristics when compared to breast cancers of epithelial origin and can be classified into two groups. The PDX model derived from one patient with MPT showed that the mouse epithelial component increased during tumour growth. Moreover, targeted inhibition of platelet-derived growth factor receptor (PDGFR) and phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) by imatinib mesylate and PKI-587 showed in vivo tumour suppression effects.

CONCLUSIONS

This study revealed the molecular profiles of MPT that can lead to molecular classification and potential targeted therapy, and suggested that the MPT PDX model can be a useful tool for studying the pathogenesis of fibroepithelial neoplasms and for preclinical drug screening to find new therapeutic strategies for MPT.

Abstract B019: Identify features of fibroblast and macrophage which regulate metastasis of triple-negative breast cancer

The tumor microenvironment (TME), which the cancer is known to remodel, can interact with cancer in various ways, such as promoting or hindering metastasis. The challenge with comprehending TME is that each patient's individual variance makes it difficult to carry out a consistent analysis. We used the PDX model to analyze the alterations entirely brought about by cancer cells of each patient in the same environment exclusively. In 121 breast cancer patients, we created a PDX model and performed WES and RNA-seq. We repeatedly performed metastatic induction tests on the models of 26 TNBC patients among the PDX models we generated. The replicated experiments confirmed that cancer cells with frequent metastasis usually spread well, while cancer cells with seldom metastases rarely metastasize. For each of the five samples that had the greatest and worst rates of metastasis, the pre-metastatic xenograft tumor was analyzed using scRNA-seq. Metastasis could not be predicted by only cancer cells because there was no difference between the two groups. Still, fibroblasts and macrophages had distinct gene markers before metastasis which can predict metastasis. To explore TME that develops pre-metastatic niches (PMN) in organs that would be metastasis targets, we developed a metastatic model using 4T1 cell lines. Daily lung macrophage RNA-seq, lung WES, and lung scRNA-seq procedures were carried out for four weeks to examine the precise timing of metastasis and the daily changes in the transcriptome. Surprisingly, a few days before the presence of any cancer cells, the gene expression of lung macrophages had already undergone significant modification. Additionally, only injections of tumor-conditioned media that mimicked metastasis could activate PMN in lung macrophages.

Citation Format: Woochan Lee, Hyewon Chung, Woohang Heo, Hyeong-Gon Moon, Seung Hyeok Seok, Jong-Il Kim. Identify features of fibroblast and macrophage which regulate metastasis of triple-negative breast cancer [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 B019.