Genetic analysis of PALB2 gene WD40 domain in canine mammary tumour patients

BACKGROUND

DNA repair mechanisms are essential for tumorigenesis and disruption of HR mechanism is an important predisposing factor of human breast cancers (BC). PALB2 is an important part of the HR. There are similarities between canine mammary tumours (CMT) and BCs. As its human counterpart, PALB2 mutations could be a predisposing factor of CMT.

OBJECTIVES

In this study, we aimed to investigate the impacts of PALB2 variants on tumorigenesis and canine mammary tumor (CMT) malignancy.

METHODS

We performed Sanger sequencing to detect germline mutations in the WD40 domain of the canine PALB2 gene in CMT patients. We conducted in silico analysis to investigate the variants, and compared the germline PALB2 mutations in humans that cause breast cancer (BC) with the variants detected in dogs with CMT.

RESULTS

We identified an intronic (c.3096+8C>G) variant, two exonic (p.A1050V and p.R1354R) variants, and a 3' UTR variant (c.4071T>C). Of these, p.R1354R and c.4071T>C novel variants were identified for the first time in this study. We found that the p.A1050V mutation had a significant effect. However, we could not determine sufficient similarity due to the differences in nucleotide/amino acid sequences between two species. Nonetheless, possible variants of human sequences in the exact location as their dog counterparts are associated with several cancer types, implying that the variants could be crucial for tumorigenesis in dogs. Our results did not show any effect of the variants on tumor malignancy.

CONCLUSIONS

The current project is the first study investigating the relationship between the PALB2 gene WD40 domain and CMTs. Our findings will contribute to a better understanding of the pathogenic mechanism of the PALB2 gene in CMTs. In humans, variant positions in canines have been linked to cancer-related phenotypes such as familial BC, endometrial tumor, and hereditary cancer predisposition syndrome. The results of bioinformatics analyses should be investigated through functional tests or case-control studies.

GATA3 functions downstream of BRCA1 to promote DNA damage repair and suppress dedifferentiation in breast cancer

BACKGROUND

Inadequate DNA damage repair promotes aberrant differentiation of mammary epithelial cells. Mammary luminal cell fate is mainly determined by a few transcription factors including GATA3. We previously reported that GATA3 functions downstream of BRCA1 to suppress aberrant differentiation in breast cancer. How GATA3 impacts DNA damage repair preventing aberrant cell differentiation in breast cancer remains elusive. We previously demonstrated that loss of p18, a cell cycle inhibitor, in mice induces luminal-type mammary tumors, whereas depletion of either Brca1 or Gata3 in p18 null mice leads to basal-like breast cancers (BLBCs) with activation of epithelial-mesenchymal transition (EMT). We took advantage of these mutant mice to examine the role of Gata3 as well as the interaction of Gata3 and Brca1 in DNA damage repair in mammary tumorigenesis.

RESULTS

Depletion of Gata3, like that of Brca1, promoted DNA damage accumulation in breast cancer cells in vitro and in basal-like breast cancers in vivo. Reconstitution of Gata3 improved DNA damage repair in Brca1-deficient mammary tumorigenesis. Overexpression of GATA3 promoted homologous recombination (HR)-mediated DNA damage repair and restored HR efficiency of BRCA1-deficient cells. Depletion of Gata3 sensitized tumor cells to PARP inhibitor (PARPi), and reconstitution of Gata3 enhanced resistance of Brca1-deficient tumor cells to PARP inhibitor.

CONCLUSIONS

These results demonstrate that Gata3 functions downstream of BRCA1 to promote DNA damage repair and suppress dedifferentiation in mammary tumorigenesis and progression. Our findings suggest that PARP inhibitors are effective for the treatment of GATA3-deficient BLBCs.

Advancing canine mammary tumor diagnostics: Unraveling the diagnostic potential of Cytokeratin 19 through droplet digital PCR analysis

Cytokeratin 19 (CK19) is a complex intracytoplasmic cytoskeletal protein primarily localized in the ducts of the mammary gland and skin epithelial cells. In humans, the expression of CK19 gene within circulating tumor cells (CTCs) extracted from blood samples of breast cancer patients reflects tumor cell activity, offering valuable insights for predicting early metastatic relapse or monitoring treatment effectiveness. However, knowledge of serum tumor markers is limited in veterinary oncology. Recently, droplet digital PCR (ddPCR), has been employed to explore rare target genes due to its heightened sensitivity and accuracy as a novel molecular diagnostic tool. The objectives of this study were to investigate the expression of the CK19 mRNA in CTCs, non-neoplastic mammary tissues, and both benign and malignant canine mammary tumors (CMTs) through ddPCR analysis. In Study I, we optimized the discard volume for blood samples to reduce CK19 contamination from skin epithelial cells post-venipuncture. The results revealed that discarding the initial 3 mL of blood was adequate and effective in eliminating CK19 mRNA contamination. In Study II, after the removal of the initial 3 mL of blood, we investigated CK19 mRNA-positive CTCs in the peripheral blood of normal healthy dogs, including those with benign and malignant CMTs. Intriguingly, CK19 mRNA was undetectable in all blood samples. The expression of CK19 mRNA in mammary tissues was investigated in Study III. The copy number (CN) ratios of the CK19 gene in non-neoplastic mammary tissues (14.77 ± 14.65) were significantly higher (P < 0.05) than those in benign (4.23 ± 3.35) and malignant groups (6.56 ± 5.64). Notably, no difference was observed between the benign and malignant groups. In conclusion, CK19 mRNA appeared unlikely to be a suitable candidate as a biomarker in the peripheral blood of CMTs, while the CN ratio in mammary tissues could serve as a potential discriminator between non-neoplastic and CMT groups, complementing the gold standard of histopathological examination.

Programmed Death-Ligand (PD-L1), Epidermal Growth Factor (EGF), Relaxin, and Matrix Metalloproteinase-3 (MMP3): Potential Biomarkers of Malignancy in Canine Mammary Neoplasia

Gene expression has been suggested as a putative tool for prognosis and diagnosis in canine mammary neoplasia (CMNs). In the present study, 58 formalin-fixed paraffin-embedded (FFPE) paraffined canine mammary neoplasias from 27 different bitches were included. Thirty-seven tumours were classified as benign, whereas thirty-one were classified as different types of canine carcinoma. In addition, mammary samples from three healthy bitches were also included. The gene expression for vascular endothelial growth factor-α (VEGFα), CD20, progesterone receptor (PGR), hyaluronidase-1 (HYAL-1), programmed death-ligand 1 (PD-L1), epidermal growth factor (EGF), relaxin (RLN2), and matrix metalloproteinase-3 (MMP3) was assessed through RT-qPCR. All the assessed genes yielded a higher expression in neoplastic mammary tissue than in healthy tissue. All the evaluated genes were overexpressed in neoplastic mammary tissue, suggesting a role in the process of tumorigenesis. Moreover, PD-L1, EGF, relaxin, and MMP3 were significantly overexpressed in malignant CMNs compared to benign CMNs, suggesting they may be useful as malignancy biomarkers.

YRNA and tRNA fragments can differentiate benign from malignant canine mammary gland tumors

Mammary gland tumors (MGT) are the most common tumors in sexually intact female dogs. The functional regulation of miRNAs, a type of noncoding RNAs (ncRNAs), in canine MGT has been extensively investigated. However, the expression of other ncRNAs, such as YRNAs and transfer RNA-derived fragments (tRFs) in canine MGT is unknown. We investigated ncRNAs other than miRNAs from our small RNA project (PRJNA716131) in different canine MGT histologic subtypes. This study included benign tumors (benign mixed tumor, complex adenoma) and malignant tumors (carcinoma in benign tumor and carcinoma with metastasis) samples. Aberrantly expressed ncRNAs were examined by comparisons among MGT subtypes. The relative expression trends were validated in canine MGT tissues, plasma, extracellular vesicles, and MGT cell lines using quantitative reverse transcription PCR. Three aberrantly expressed ncRNAs were identified by comparisons among MGT subtypes. YRNA and tRNA-Gly-GCC distinguished benign mixed tumor from other MGT histologic subtypes, while tRNA-Val differentiated complex adenoma, carcinoma in benign tumors, and carcinoma with metastasis. The ROC curve of the three ncRNAs showed they might be potential biomarkers to discriminate malignant from benign MGT. YRNA and tRFs expression levels were decreased in metastatic compared with primary canine MGT cell lines. To the best of our knowledge, this is the first investigation of YRNA and tRFs in canine MGT. The three identified ncRNAs may be biomarkers for differentiating MGT histologic subtypes. Suggested Reviewers: Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporatio.

Time of day bias for biological sampling in studies of mammary cancer

Despite its demonstrated biological significance, time of day is a broadly overlooked biological variable in preclinical and clinical studies. How time of day affects the influence of peripheral tumors on central (brain) function remains unspecified. Thus, we tested the hypothesis that peripheral mammary cancer tumors alter the transcriptome of immune responses in the brain and that these responses vary based on time of day; we predicted that time of day sampling bias would alter the interpretation of the results. Brain tissues collected at mid dark and mid light from mammary tumor-bearing and vehicle injected mice were analyzed using the Nanostring nCounter immune panel. Peripheral mammary tumors significantly affected expression within the brain of over 100 unique genes of the 770 represented in the panel, and fewer than 25% of these genes were affected similarly across the day. Indeed, between 65 and 75% of GO biological processes represented by the differentially expressed genes were dependent upon time of day of sampling. The implications of time-of-day sampling bias in interpretation of research studies cannot be understated. We encourage considering time of day as a significant biological variable in studies and to appropriately control for it and clearly report time of day in findings.

Conditional in vivo deletion of LYN kinase has little effect on a BRCA1 loss-of-function-associated mammary tumour model

LYN kinase is expressed in BRCA1 loss-of-function-dependent mouse mammary tumours, in the cells of origin of such tumours, and in human breast cancer. Suppressing LYN kinase activity in BRCA1-defective cell lines as well as in in vitro cultures of Brca1-null mouse mammary tumours is deleterious to their growth. Here, we examined the interaction between LYN kinase and BRCA1 loss-of-function in an in vivo mouse mammary tumour model, using conditional knockout Brca1 and Lyn alleles. Comparison of Brca1 tumour cohorts showed little difference in mammary tumour formation between animals that were wild type, heterozygous or homozygous for the conditional Lyn allele, although this was confounded by factors including incomplete Lyn recombination in some tumours. RNA-sequencing analysis demonstrated that tumours with high levels of Lyn gene expression had a slower doubling time, but this was not correlated with levels of LYN staining in tumour cells themselves. Rather, high Lyn expression and slower tumour growth were likely a result of B-cell infiltration. The multifaceted role of LYN indicates that it is likely to present difficulties as a therapeutic target in breast cancer.

Matrine Targets BTF3 to Inhibit the Growth of Canine Mammary Tumor Cells

The canine mammary tumor model is more suitable for studying human breast cancer, and the safety concentrations of matrine and the biotin-labeled matrine probe were determined in canine primary mammary epithelial cells, and then selected canine mammary tumor cell lines CHMm and CHMp were incubated with matrine, and cell viability was detected by CCK-8. The biotin-labeled matrine probe was used to pull-down the targets of matrine in canine mammary tumor cells, and the targets were screened in combination with activity-based protein profiling (ABPP) and Genecards database, and verified by qPCR and western blot. The results showed that the maximum non-cytotoxic concentrations of matrine and biotin-labeled matrine probe in canine primary mammary epithelial cells were 250 μg/mL and 500 μg/mL, respectively. Matrine and biotin-labeled matrine probe had a proliferation inhibitory effect time-dependently on CHMm and CHMp cells within a safe concentration range, and induced autophagy in cells. Then BTF3 targets were obtained by applying ABPP and Genecards screening. Cellular thermal shift assay (CETSA) findings indicated that matrine could increase the heat stability of BTF3 protein. Pull-down employing biotin-labeled matrine probe with CHMm and CHMp cell lysates revealed that BTF3 protein was detected in the biotin-labeled matrine probe group and that BTF3 protein was significantly decreased by the addition of matrine. The qPCR and western blot findings of CHMm and CHMp cells treated with matrine revealed that matrine decreased the expression of the BTF3 gene and protein with the extension of the action time, and the impact was more substantial at the protein level, respectively.

Research progress of good markers for canine mammary carcinoma

PURPOSE

Mammary gland tumors are the most common neoplastic diseases in elderly female dogs, about 50% of which are considered to be malignant. Canine mammary tumors are similar to human breast cancers in many respects, so canine mammary tumors are frequently studied alongside human breast cancer. This article mentioned KI-67, HER-2, COX-2, BRCA1, BRCA2, P53, CA15-3, MicroRNA, Top2α and so on. All these markers are expected to have an important role in the clinic.

METHODS

Existing markers of canine mammary carcinoma are reviewed, and the expression of each marker and its diagnostic role for this tumor are described in detail.

RESULTS

This article introduced several effective markers of canine mammary tumors, among them, antigen KI-67 (KI-67), human epidermal growth factor receptor 2 (HER-2), cyclooxygenase 2 (COX-2) are promising and can be detected in both serum and tissue samples. Breast cancer caused by mutations in the breast cancer 1 gene (BRCA1) and breast cancer 2 gene (BRCA2) is also a hot topic of research. In addition to the above symbols, tumor protein p53 (p53), cancer antigen15-3 (CA15-3), MicroRNA (miRNA), topoisomerase πα (Top2α), proliferating cell nuclear antigen (PCNA), epidermal growth factor receptor (EGFR) and E-cadherin will also be involved in this paper. We will also mention Mammaglobin, which has been rarely reported so far.

A genetic mosaic mouse model illuminates the pre-malignant progression of basal-like breast cancer

Basal-like breast cancer (BLBC) is highly aggressive, and often characterized by BRCA1 and p53 deficiency. Although conventional mouse models enabled the investigation of BLBC at malignant stages, its initiation and pre-malignant progression remain understudied. Here, we leveraged a mouse genetic system known as mosaic analysis with double markers (MADM) to study BLBC initiation by generating rare GFP+Brca1, p53-deficient mammary cells alongside RFP+ wild-type sibling cells. After confirming the close resemblance of mammary tumors arising in this model to human BLBC at both transcriptomic and genomic levels, we focused our studies on the pre-malignant progression of BLBC. Initiated GFP+ mutant cells showed a stepwise pre-malignant progression trajectory from focal expansion to hyper-alveolarization and then to micro-invasion. Furthermore, despite morphological similarities to alveoli, hyper-alveolarized structures actually originate from ductal cells based on twin-spot analysis of GFP-RFP sibling cells. Finally, luminal-to-basal transition occurred exclusively in cells that have progressed to micro-invasive lesions. Our MADM model provides excellent spatiotemporal resolution to illuminate the pre-malignant progression of BLBC, and should enable future studies on early detection and prevention for this cancer.

Human basal-like breast cancer is represented by one of the two mammary tumor subtypes in dogs

BACKGROUND

About 20% of breast cancers in humans are basal-like, a subtype that is often triple-negative and difficult to treat. An effective translational model for basal-like breast cancer is currently lacking and urgently needed. To determine whether spontaneous mammary tumors in pet dogs could meet this need, we subtyped canine mammary tumors and evaluated the dog-human molecular homology at the subtype level.

METHODS

We subtyped 236 canine mammary tumors from 3 studies by applying various subtyping strategies on their RNA-seq data. We then performed PAM50 classification with canine tumors alone, as well as with canine tumors combined with human breast tumors. We identified feature genes for human BLBC and luminal A subtypes via machine learning and used these genes to repeat canine-alone and cross-species tumor classifications. We investigated differential gene expression, signature gene set enrichment, expression association, mutational landscape, and other features for dog-human subtype comparison.

RESULTS

Our independent genome-wide subtyping consistently identified two molecularly distinct subtypes among the canine tumors. One subtype is mostly basal-like and clusters with human BLBC in cross-species PAM50 and feature gene classifications, while the other subtype does not cluster with any human breast cancer subtype. Furthermore, the canine basal-like subtype recaptures key molecular features (e.g., cell cycle gene upregulation, TP53 mutation) and gene expression patterns that characterize human BLBC. It is enriched in histological subtypes that match human breast cancer, unlike the other canine subtype. However, about 33% of canine basal-like tumors are estrogen receptor negative (ER-) and progesterone receptor positive (PR+), which is rare in human breast cancer. Further analysis reveals that these ER-PR+ canine tumors harbor additional basal-like features, including upregulation of genes of interferon-γ response and of the Wnt-pluripotency pathway. Interestingly, we observed an association of PGR expression with gene silencing in all canine tumors and with the expression of T cell exhaustion markers (e.g., PDCD1) in ER-PR+ canine tumors.

CONCLUSIONS

We identify a canine mammary tumor subtype that molecularly resembles human BLBC overall and thus could serve as a vital translational model of this devastating breast cancer subtype. Our study also sheds light on the dog-human difference in the mammary tumor histology and the hormonal cycle.

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.

New oncogenic functions of LINE1 retroelement as a ceRNA for tumor suppressive microRNA miR-126 on ENPP5

Retroelements (REs) had been considered 'Junk' until the encyclopedia of DNA elements (ENCODE) project demonstrated that most genome is functional. Although the function of retroelements has been reported in diverse cancers including human breast cancer (HBC) and subtypes, only a few studies have suggested the putative functions of REs via their random genome integration. A canine mammary tumor (CMT) has been highlighted due to the similarities in molecular and pathophysiology with HBC. This study investigated the putative roles of REs common in both HBC and CMT. The human LINE and HERV-K sequences harbor many miRNAs responsive elements (MREs) for tumor-suppressive miRNA such as let-7. We also observed that various MREs are exist in the ERV and LINE highly expressed in the transcriptome data of CMT as well as HBC sets. MREs against miR-126 were highly expressed in both HBC and CMT while the levels of miR-126 were down-regulated. Oppositely, the expression of miR-126 target genes was significantly up-regulated in the cancers. Moreover, cancer patients with an increased level of miR-126 showed better overall survival. The expression of ENPP5, a putative miR-126 target gene, was downregulated by miR-126 mimic. Importantly, overexpression of LINE fragment significantly suppressed miR-126 function on the target gene expression. We propose the functional role of REs expression in tumorigenesis as competing endogenous RNAs (ceRNA) against tumor-suppressive miRNAs. This study provided pieces of evidence that LINE expression, even partial and fragmented, have a regulatory function in ENPP5 gene expression via the competition with miR-126.

RHAMM regulates MMTV-PyMT-induced lung metastasis by connecting STING-dependent DNA damage sensing to interferon/STAT1 pro-apoptosis signaling

BACKGROUND

RHAMM is a multifunctional protein that is upregulated in breast tumors, and the presence of strongly RHAMM+ve cancer cell subsets associates with elevated risk of peripheral metastasis. Experimentally, RHAMM impacts cell cycle progression and cell migration. However, the RHAMM functions that contribute to breast cancer metastasis are poorly understood.

METHODS

We interrogated the metastatic functions of RHAMM using a loss-of-function approach by crossing the MMTV-PyMT mouse model of breast cancer susceptibility with Rhamm-/- mice. In vitro analyses of known RHAMM functions were performed using primary tumor cell cultures and MMTV-PyMT cell lines. Somatic mutations were identified using a mouse genotyping array. RNA-seq was performed to identify transcriptome changes resulting from Rhamm-loss, and SiRNA and CRISPR/Cas9 gene editing was used to establish cause and effect of survival mechanisms in vitro.

RESULTS

Rhamm-loss does not alter initiation or growth of MMTV-PyMT-induced primary tumors but unexpectedly increases lung metastasis. Increased metastatic propensity with Rhamm-loss is not associated with obvious alterations in proliferation, epithelial plasticity, migration, invasion or genomic stability. SNV analyses identify positive selection of Rhamm-/- primary tumor clones that are enriched in lung metastases. Rhamm-/- tumor clones are characterized by an increased ability to survive with ROS-mediated DNA damage, which associates with blunted expression of interferon pathway and target genes, particularly those implicated in DNA damage-resistance. Mechanistic analyses show that ablating RHAMM expression in breast tumor cells by siRNA knockdown or CRISPR-Cas9 gene editing blunts interferon signaling activation by STING agonists and reduces STING agonist-induced apoptosis. The metastasis-specific effect of RHAMM expression-loss is linked to microenvironmental factors unique to tumor-bearing lung tissue, notably high ROS and TGFB levels. These factors promote STING-induced apoptosis of RHAMM+ve tumor cells to a significantly greater extent than RHAMM-ve comparators. As predicted by these results, colony size of Wildtype lung metastases is inversely related to RHAMM expression.

CONCLUSION

RHAMM expression-loss blunts STING-IFN signaling, which offers growth advantages under specific microenvironmental conditions of lung tissue. These results provide mechanistic insight into factors controlling clonal survival/expansion of metastatic colonies and has translational potential for RHAMM expression as a marker of sensitivity to interferon therapy.

PI3Kβ controls immune evasion in PTEN-deficient breast tumours

Loss of the PTEN tumour suppressor is one of the most common oncogenic drivers across all cancer types1. PTEN is the major negative regulator of PI3K signalling. The PI3Kβ isoform has been shown to play an important role in PTEN-deficient tumours, but the mechanisms underlying the importance of PI3Kβ activity remain elusive. Here, using a syngeneic genetically engineered mouse model of invasive breast cancer driven by ablation of both Pten and Trp53 (which encodes p53), we show that genetic inactivation of PI3Kβ led to a robust anti-tumour immune response that abrogated tumour growth in syngeneic immunocompetent mice, but not in immunodeficient mice. Mechanistically, PI3Kβ inactivation in the PTEN-null setting led to reduced STAT3 signalling and increased the expression of immune stimulatory molecules, thereby promoting anti-tumour immune responses. Pharmacological PI3Kβ inhibition also elicited anti-tumour immunity and synergized with immunotherapy to inhibit tumour growth. Mice with complete responses to the combined treatment displayed immune memory and rejected tumours upon re-challenge. Our findings demonstrate a molecular mechanism linking PTEN loss and STAT3 activation in cancer and suggest that PI3Kβ controls immune escape in PTEN-null tumours, providing a rationale for combining PI3Kβ inhibitors with immunotherapy for the treatment of PTEN-deficient breast cancer.

Role of a Mixture of Polyphenol Compounds Released after Blueberry Fermentation in Chemoprevention of Mammary Carcinoma: In Vivo Involvement of miR-145

Epigenetic mechanisms such as microRNA (miRNA) deregulation seem to exert a central role in breast cancer initiation and progression. Therefore, targeting epigenetics deregulation may be an effective strategy for preventing and halting carcinogenesis. Studies have revealed the significant role of naturally occurring polyphenolic compounds derived from fermented blueberry fruits in cancer chemoprevention by modulation of cancer stem cell development through the epigenetic mechanism and regulation of cellular signaling pathways. In this study, we first investigated the phytochemical changes during the blueberry fermentation process. Fermentation favored the release of oligomers and bioactive compounds such as protocatechuic acid (PCA), gallic acid, and catechol. Next, we investigated the chemopreventive potentials of a polyphenolic mixture containing PCA, gallic acid, and catechin found in fermented blueberry juice in a breast cancer model by measuring miRNA expression and the signaling pathways involved in breast cancer stemness and invasion. To this end, 4T1 and MDA-MB-231 cell lines were treated with different doses of the polyphenolic mixture for 24 h. Additionally, female Balb/c mice were fed with this mixture for five weeks; two weeks before and three weeks after receiving 4T1 cells. Mammosphere formation was assayed in both cell lines and the single-cell suspension obtained from the tumor. Lung metastases were counted by isolating 6-thioguanine-resistant cells present in the lungs. In addition, we conducted RT-qPCR and Western blot analysis to validate the expression of targeted miRNAs and proteins, respectively. We found a significant reduction in mammosphere formation in both cell lines treated with the mixture and in tumoral primary cells isolated from mice treated with the polyphenolic compound. The number of colony-forming units of 4T1 cells in the lungs was significantly lower in the treatment group compared to the control group. miR-145 expression significantly increased in the tumor samples of mice treated with the polyphenolic mixture compared to the control group. Furthermore, a significant increase in FOXO1 levels was noted in both cell lines treated with the mixture. Overall, our results show that phenolic compounds found in fermented blueberry delay the formation of tumor-initiating cells in vitro and in vivo and reduce the spread of metastatic cells. The protective mechanisms seem to be related, at least partly, to the epigenetic modulation of mir-145 and its signaling pathways.

PIK3CA is recurrently mutated in canine mammary tumors, similarly to in human mammary neoplasia

Biological features of neoplastic disease affecting mammary gland tissue are shared between canines and humans. Research performed in either species has translational value and early phase clinical trials performed in canines with spontaneous disease could be informative for human trials. The purpose of this study was to investigate the somatic genetic aberrations occurring in canine mammary neoplasia by exome capture and next generation sequencing. Based on 55 tumor-normal pairs we identified the PIK3CA gene as the most commonly mutated gene in canine mammary tumors, with 25% of samples carrying mutations in this gene. A recurrent missense mutation was identified, p.H1047R, which is homologous to the human PIK3CA hotspot mutation found in different types of breast neoplasia. Mutations homologous to other known human mutation hotspots such as the PIK3CA p.E545K and the KRAS p.G12V/D were also identified. We identified copy number aberrations affecting important tumor suppressor and oncogenic pathways including deletions affecting the PTEN tumor suppressor gene. We suggest that activation of the KRAS or PIK3CA oncogenes or loss of the PTEN suppressor gene may be important for mammary tumor development in dogs. This data endorses the conservation of cancer across species and the validity of studying cancer in non-human species.

Multiomics in primary and metastatic breast tumors from the AURORA US network finds microenvironment and epigenetic drivers of metastasis

The AURORA US Metastasis Project was established with the goal to identify molecular features associated with metastasis. We assayed 55 females with metastatic breast cancer (51 primary cancers and 102 metastases) by RNA sequencing, tumor/germline DNA exome and low-pass whole-genome sequencing and global DNA methylation microarrays. Expression subtype changes were observed in ~30% of samples and were coincident with DNA clonality shifts, especially involving HER2. Downregulation of estrogen receptor (ER)-mediated cell-cell adhesion genes through DNA methylation mechanisms was observed in metastases. Microenvironment differences varied according to tumor subtype; the ER+/luminal subtype had lower fibroblast and endothelial content, while triple-negative breast cancer/basal metastases showed a decrease in B and T cells. In 17% of metastases, DNA hypermethylation and/or focal deletions were identified near HLA-A and were associated with reduced expression and lower immune cell infiltrates, especially in brain and liver metastases. These findings could have implications for treating individuals with metastatic breast cancer with immune- and HER2-targeting therapies.

Satellite Noncoding RNAs (ncRNA) as Cancer Biomarkers? New Insights from FA-SAT ncRNA Molecular and Clinical Profiles in Feline Mammary Tumors

Satellite noncoding RNAs (ncRNAs) are a new frontier of cancer biology research and biomarkers. While the knowledge on ncRNAs in human cancers is still limited, studies in other species can be informative to guide future translational research and development for cancer molecular targets and diagnostics. In this context, FA-SAT is the major satellite DNA of the cat genome, which is also present in humans, being transcribed in both species. In this study, we report new insights on FA-SAT (DNA and RNA) profile in feline mammary tumors, using disease-free tissues from the same animals as reference. We quantified the FA-SAT DNA and RNA levels (long and small transcripts) by real-time quantitative polymerase chain reaction (qPCR) and RT-qPCR. The comparison of the FA-SAT DNA and RNA levels with clinicopathological parameters revealed several associations, such as (1) the FA-SAT DNA levels' positive relation with lymphovascular invasion, (2) the FA-SAT long RNA negative correlation with Ki-67 index, and its positive association with Estrogen Receptor status, and (3) the FA-SAT small RNA level positive correlation with tumor size and skin ulceration. Also, FA-SAT long RNA is correlated with ERBB2 and c-MYC RNA levels. These data collectively suggest that FA-SAT ncRNA offers prospects as a potential cancer biomarker in cats. Further studies in humans are also needed to decipher the emerging role of ncRNAs in cancer biology and precision medicine fields. This work brings new information on the relation of FA-SAT ncRNAs with the oncogenic process, uncovering a new potential cancer biomarker.

Preliminary evaluation of a small interfering RNA molecular probe targeting murine double minute 2 in breast cancer

INTRODUCTION

Murine double minute 2 (MDM2) is an oncogene that is important in tumorigenesis, tumor metastasis and chemotherapy resistance. We aimed to synthesize a molecular imaging probe, 99m Tc-HYNIC-siRNA 1489, which could specifically bind to MDM2. The [ 99m Tc]HYNIC-siRNA 1489 molecular probe provided an effective way of assessing MDM2 expression via single-photon emission computed tomography.

METHOD

Three siRNAs were designed, and their inhibitory efficiencies were determined using western blots and qRT-PCR. The selected siRNA was labeled with the radionuclide technetium-99m ( 99m Tc) through the chelator HYNIC. The bioactivity and properties of [ 99m Tc]HYNIC-siRNA 1489 were evaluated prior to imaging in mice. Imaging and biodistribution of the probe were used to assess its targeting ability.

RESULTS

SiRNA 1489, which was labeled with 99m Tc, displayed a strong inhibitory effect in Michigan Cancer Foundation-7 cell lines. The radiochemical purity of [ 99m Tc]HYNIC-siRNA 1489 was stable at various temperatures in phosphate-buffered serum and bovine serum. The tumor/muscle ratio in mice injected with [ 99m Tc]HYNIC-siRNA 1489 was higher than that in those injected with the negative control, [ 99m Tc]HYNIC-NC siRNA. The percentage injected dose per gram (%ID/g) of the tumors injected with 99m Tc-HYNIC-siRNA 1489 was greater than that of the control group.

CONCLUSION

The [ 99m Tc]HYNIC-siRNA 1489 was taken up by the tumor, which had a high level of MDM2. The probe exhibited a sufficient retention time in the tumor. This probe may be an effective strategy for evaluating MDM2 expression and achieving early diagnosis in breast cancer.

Induced mammary cancer in rat models: pathogenesis, genetics, and relevance to female breast cancer

Mammary cancer, or breast cancer in women, is a polygenic disease with a complex etiopathogenesis. While much remains elusive regarding its origin, it is well established that chemical carcinogens and endogenous estrogens contribute significantly to the initiation and progression of this disease. Rats have been useful models to study induced mammary cancer. They develop mammary tumors with comparable histopathology to humans and exhibit differences in resistance or susceptibility to mammary cancer depending on strain. While some rat strains (e.g., Sprague-Dawley) readily form mammary tumors following treatment with the chemical carcinogen, 7,12-dimethylbenz[a]-anthracene (DMBA), other strains (e.g., Copenhagen) are resistant to DMBA-induced mammary carcinogenesis. Genetic linkage in inbred strains has identified strain-specific quantitative trait loci (QTLs) affecting mammary tumors, via mechanisms that act together to promote or attenuate, and include 24 QTLs controlling the outcome of chemical induction, 10 QTLs controlling the outcome of estrogen induction, and 4 QTLs controlling the outcome of irradiation induction. Moreover, and based on shared factors affecting mammary cancer etiopathogenesis between rats and humans, including orthologous risk regions between both species, rats have served as useful models for identifying methods for breast cancer prediction and treatment. These studies in rats, combined with alternative animal models that more closely mimic advanced stages of breast cancer and/or human lifestyles, will further improve our understanding of this complex disease.

Comparative analysis of the molecular subtype landscape in canine and human mammary gland tumors

Breast cancers in humans belong to one of several intrinsic molecular subtypes each with different tumor biology and different clinical impact. Mammary gland tumors in dogs are proposed as a relevant comparative model for human breast cancer; however, it is still unclear whether the intrinsic molecular subtypes have the same significance in dogs and humans. Using publicly available data, we analyzed gene expression and whole-exome sequencing data from 158 canine mammary gland tumors. We performed molecular subtyping using the PAM50 method followed by subtype-specific comparisons of gene expression characteristics, mutation patterns and copy number profiles between canine tumors and human breast tumors from The Cancer Genome Atlas (TCGA) breast cancer cohort (n = 1097). We found that luminal A canine tumors greatly resemble luminal A human tumors both in gene expression characteristics, mutations and copy number profiles. Also, the basal-like canine and human tumors were relatively similar, with low expression of luminal epithelial markers and high expression of genes involved in cell proliferation. There were, however, distinct differences in immune-related gene expression patterns in basal-like tumors between the two species. Characteristic HER2-enriched and luminal B subtypes were not present in the canine cohort, and we found no tumors with high-level ERBB2 amplifications. Benign and malignant canine tumors displayed similar PAM50 subtype characteristics. Our findings indicate that deeper understanding of the different molecular subtypes in canine mammary gland tumors will further improve the value of canines as comparative models for human breast cancer.

The Role of the C-Terminal Lysine of S100P in S100P-Induced Cell Migration and Metastasis

S100P protein is a potent inducer of metastasis in a model system, and its presence in cancer cells of patients is strongly associated with their reduced survival times. A well-established Furth Wistar rat metastasis model system, methods for measuring cell migration, and specific inhibitors were used to study pathways of motility-driven metastasis. Cells expressing C-terminal mutant S100P proteins display markedly-reduced S100P-driven metastasis in vivo and cell migration in vitro. These cells fail to display the low focal adhesion numbers observed in cells expressing wild-type S100P, and the mutant S100P proteins exhibit reduced biochemical interaction with non-muscle myosin heavy chain isoform IIA in vitro. Extracellular inhibitors of the S100P-dependent plasminogen activation pathway reduce, but only in part, wild-type S100P-dependent cell migration; they are without effect on S100P-negative cells or cells expressing C-terminal mutant S100P proteins and have no effect on the numbers of focal adhesions. Recombinant wild-type S100P protein, added extracellularly to S100P-negative cells, stimulates cell migration, which is abolished by these inhibitors. The results identify at least two S100P-dependent pathways of migration, one cell surface and the other intracellularly-linked, and identify its C-terminal lysine as a target for inhibiting multiple migration-promoting activities of S100P protein and S100P-driven metastasis.

Deletion of Col15a1 Modulates the Tumour Extracellular Matrix and Leads to Increased Tumour Growth in the MMTV-PyMT Mouse Mammary Carcinoma Model

Basement membrane (BM) zone-associated collagen XV (ColXV) has been shown to suppress the malignancy of tumour cells, and its restin domain can inhibit angiogenesis. In human breast cancer, as well as in many other human carcinomas, ColXV is lost from the epithelial BM zone prior to tumour invasion. Here, we addressed the roles of ColXV in breast carcinogenesis using the transgenic MMTV-PyMT mouse mammary carcinoma model. We show here for the first time that the inactivation of Col15a1 in mice leads to changes in the fibrillar tumour matrix and to increased mammary tumour growth. ColXV is expressed by myoepithelial and endothelial cells in mammary tumours and is lost from the ductal BM along with the loss of the myoepithelial layer during cancer progression while persisting in blood vessels and capillaries, even in invasive tumours. However, despite the absence of anti-angiogenic restin domain, neovascularisation was reduced rather than increased in the ColXV-deficient mammary tumours compared to controls. We also show that, in robust tumour cell transplantation models or in a chemical-induced fibrosarcoma model, the inactivation of Col15a1 does not affect tumour growth or angiogenesis. In conclusion, our results support the proposed tumour suppressor function of ColXV in mammary carcinogenesis and reveal diverse roles of this collagen in different cancer types.

Co-exposure to BPA and DEHP enhances susceptibility of mammary tumors via up-regulating Esr1/HDAC6 pathway in female rats

Breast cancer (BrCa) as one of the major malignancies threatening women's health worldwide occurs due to the genetic and environmental interactions. Epidemiological studies have suggested that exposure to endocrine disrupting chemicals (EDCs) can elevate the risk of breast cancer. Di-(2-ethylhexyl)-phthalate (DEHP) and bisphenol A (BPA) are known as two typical EDCs. Although several studies have implied that there appear to have adverse effects of exposure to BPA or DEHP alone on breast development, no study to date has demonstrated the exact toxic effect of combined exposure to DEHP and BPA on breast tumorigenesis. In the present study, we performed an in vivo experiment including 160 female Sprague-Dawley (SD) rats, in which 80 rats were randomly allocated to 4 groups including control group given to normal diet, DEHP (150 mg/kg body weight/day), BPA (20 mg/kg body weight/day), and DEHP (150 mg/kg body weight/day) combined with BPA (20 mg/kg body weight/day) by gavage for 30 weeks. Additionally, a DEN/MNU/DHPN (DMD)-induced carcinogenesis animal model was also established to assess their effect on tumor promotion. Namely, the other 80 SD rats were separated into another 4 groups: in addition to DMD initiation each group treated with vehicle, DEHP, BPA and the combination of BPA and DEHP respectively. Our data demonstrated that BPA alone or in combination with DEHP may induce hyperplasia of mammary glands, including the proliferation of ductal epithelial cells and an increase in the number of lobules and acinus after a 30-week exposure. Notably, co-exposure to DEHP and BPA increased the incidence and reduced the latency of mammary tumor, which seemed to enhance the susceptibility of carcinogens-induced tumor. Mechanistically, our results supported the hypothesis that exposure to BPA and DEHP might promote breast cancer dependent on Esr1 and HDAC6 as pivotal factors, and further lead to the activation of oncogene c-Myc. Our study suggested that BPA combined with DEHP facilitate the occurrence of mammary tumors, which contributed to advance our understanding in the complex effects of compound exposure to endocrine disrupting chemicals.

Morphological screening of mesenchymal mammary tumor organoids to identify drugs that reverse epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) has been implicated in conferring stem cell properties and therapeutic resistance to cancer cells. Therefore, identification of drugs that can reprogram EMT may provide new therapeutic strategies. Here, we report that cells derived from claudin-low mammary tumors, a mesenchymal subtype of triple-negative breast cancer, exhibit a distinctive organoid structure with extended "spikes" in 3D matrices. Upon a miR-200 induced mesenchymal-epithelial transition (MET), the organoids switch to a smoother round morphology. Based on these observations, we developed a morphological screening method with accompanying analytical pipelines that leverage deep neural networks and nearest neighborhood classification to screen for EMT-reversing drugs. Through screening of a targeted epigenetic drug library, we identified multiple class I HDAC inhibitors and Bromodomain inhibitors that reverse EMT. These data support the use of morphological screening of mesenchymal mammary tumor organoids as a platform to identify drugs that reverse EMT.

Cholesteryl Ester Promotes Mammary Tumor Growth in MMTV-PyMT Mice and Activates Akt-mTOR Pathway in Tumor Cells

The association between intratumoral cholesteryl ester (CE) and tumor progression has been reported previously. The objective of our study was to investigate a causal effect of CE on mammary tumor progression. Using MMTV-PyMT (MMTV-polyoma virus middle T) transgenic mice and breast tumor cell MCF-7, we show that both exogenous and endogenous CE can increase mammary tumor growth, that CE upregulates the AKT/mTOR pathway, and that CE synthesis blockade suppresses this signaling pathway. Our data suggest that SOAT1, a sterol O-acyltransferase, may be a potential target for the treatment of breast cancer.

MRCKα Is Dispensable for Breast Cancer Development in the MMTV-PyMT Model

MRCKα is a ubiquitously expressed serine/threonine kinase involved in cell contraction and F-actin turnover, which is highly amplified in human breast cancer and part of a gene expression signature for bad prognosis. Nothing is known about the in vivo function of MRCKα. To explore MRCKα function in development and in breast cancer, we generated mice lacking a functional MRCKα gene. Mice were born close to the Mendelian ratio and showed no obvious phenotype including a normal mammary gland formation. Assessing breast cancer development using the transgenic MMTV-PyMT mouse model, loss of MRCKα did not affect tumor onset, tumor growth and metastasis formation. Deleting MRCKα and its related family member MRCKβ in two triple-negative breast cancer cell lines resulted in reduced invasion of MDA-MB-231 cells, but did not affect migration of 4T1 cells. Further genomic analysis of human breast cancers revealed that MRCKα is frequently co-amplified with the oncogenes ARID4B and AKT3 which might contribute to the prognostic value of MRCKα expression. Collectively, these data suggest that MRCKα might be a prognostic marker for breast cancer, but probably of limited functional importance.

Single-cell transcriptomics reveals involution mimicry during the specification of the basal breast cancer subtype

Basal breast cancer is associated with younger age, early relapse, and a high mortality rate. Here, we use unbiased droplet-based single-cell RNA sequencing (RNA-seq) to elucidate the cellular basis of tumor progression during the specification of the basal breast cancer subtype from the luminal progenitor population in the MMTV-PyMT (mouse mammary tumor virus-polyoma middle tumor-antigen) mammary tumor model. We find that basal-like cancer cells resemble the alveolar lineage that is specified upon pregnancy and encompass the acquisition of an aberrant post-lactation developmental program of involution that triggers remodeling of the tumor microenvironment and metastatic dissemination. This involution mimicry is characterized by a highly interactive multicellular network, with involution cancer-associated fibroblasts playing a pivotal role in extracellular matrix remodeling and immunosuppression. Our results may partially explain the increased risk and poor prognosis of breast cancer associated with childbirth.

Reduction of fibrosis and immune suppressive cells in ErbB2-dependent tumorigenesis by an LXR agonist

One of the central challenges for cancer therapy is the identification of factors in the tumor microenvironment that increase tumor progression and prevent immune surveillance. One such element associated with breast cancer is stromal fibrosis, a histopathologic criterion for invasive cancer and poor survival. Fibrosis is caused by inflammatory factors and remodeling of the extracellular matrix that elicit an immune tolerant microenvironment. To address the role of fibrosis in tumorigenesis, we developed NeuT/ATTAC transgenic mice expressing a constitutively active NeuT/erbB2 transgene, and an inducible, fat-directed caspase-8 fusion protein, which upon activation results in selective and partial ablation of mammary fat and its replacement with fibrotic tissue. Induction of fibrosis in NeuT/ATTAC mice led to more rapid tumor development and an inflammatory and fibrotic stromal environment. In an effort to explore therapeutic options that could reduce fibrosis and immune tolerance, mice were treated with the oxysterol liver X receptor (LXR) pan agonist, N,N-dimethyl-3-β-hydroxy-cholenamide (DMHCA), an agent known to reduce fibrosis in non-malignant diseases. DMHCA reduced tumor progression, tumor multiplicity and fibrosis, and improved immune surveillance by reducing infiltrating myeloid-derived suppressor cells and increasing CD4 and CD8 effector T cells. These effects were associated with downregulation of an LXR-dependent gene network related to reduced breast cancer survival that included Spp1, S100a9, Anxa1, Mfge8 and Cd14. These findings suggest that the use of DMHCA may be a potentially effective approach to reduce desmoplasia and immune tolerance and increase the efficacy of cancer therapy.

RNF168 regulates R-loop resolution and genomic stability in BRCA1/2-deficient tumors

Germline mutations in BRCA1 and BRCA2 (BRCA1/2) genes considerably increase breast and ovarian cancer risk. Given that tumors with these mutations have elevated genomic instability, they exhibit relative vulnerability to certain chemotherapies and targeted treatments based on poly (ADP-ribose) polymerase (PARP) inhibition. However, the molecular mechanisms that influence cancer risk and therapeutic benefit or resistance remain only partially understood. BRCA1 and BRCA2 have also been implicated in the suppression of R-loops, triple-stranded nucleic acid structures composed of a DNA:RNA hybrid and a displaced ssDNA strand. Here, we report that loss of RNF168, an E3 ubiquitin ligase and DNA double-strand break (DSB) responder, remarkably protected Brca1-mutant mice against mammary tumorigenesis. We demonstrate that RNF168 deficiency resulted in accumulation of R-loops in BRCA1/2-mutant breast and ovarian cancer cells, leading to DSBs, senescence, and subsequent cell death. Using interactome assays, we identified RNF168 interaction with DHX9, a helicase involved in the resolution and removal of R-loops. Mechanistically, RNF168 directly ubiquitylated DHX9 to facilitate its recruitment to R-loop-prone genomic loci. Consequently, loss of RNF168 impaired DHX9 recruitment to R-loops, thereby abrogating its ability to resolve R-loops. The data presented in this study highlight a dependence of BRCA1/2-defective tumors on factors that suppress R-loops and reveal a fundamental RNF168-mediated molecular mechanism that governs cancer development and vulnerability.

Oncolytic adenovirus encoding LIGHT (TNFSF14) inhibits tumor growth via activating anti-tumor immune responses in 4T1 mouse mammary tumor model in immune competent syngeneic mice

LIGHT, also known as tumor-necrosis factor (TNF) superfamily member 14 (TNFSF14), is predominantly expressed on activated immune cells and some tumor cells. LIGHT is a pivotal regulator both for recruiting and activating immune cells in the tumor lesions. In this study, we armed human telomerase reverse transcriptase (TERT) promoter controlled oncolytic adenovirus with LIGHT to generate rAd.Light. rAd.Light effectively transduced both human and mouse breast tumor cell lines in vitro, and expressed LIGHT protein on the surface of tumor cells. Both rAd.Null, and rAd.Light could replicate in human breast cancer cells, and produced cytotoxicity to human and mouse mammary tumor cells. rAd.Light induced apoptosis resulting in tumor cell death. Using a subcutaneous model of 4T1 cells in BALB/c mice, rAd.Light was delivered intratumorally to evaluate the anti-tumor responses. Both rAd.Light and rAd.Null significantly inhibited the tumor growth, but rAd.Light produced much stronger anti-tumor effects. Histopathological analysis showed the infiltration of T lymphocytes in the tumor tissues. rAd.Light also induced stronger cellular apoptosis than rAd.Null in the tumors. Interestingly, on day 15, compared to rAd.Null, there was a significant reduction of Tregs following rAd.Light treatment. rAd.Light significantly increased Th1 cytokine interleukin (IL)-2 expression, and reduced Th2 cytokines expression, such as transforming growth factor β (TGF-β) and IL-10 in the tumors. These results suggest rAd.Light induced activation of anti-tumor immune responses. In conclusion, rAd.Light produced anti-tumor effect in a subcutaneous model of breast cancer via inducing tumor apoptosis and evoking strong anti-tumor immune responses. Therefore, rAd.Light has great promise to be developed as an effective therapeutic approach for the treatment of breast cancer.

Leptin Modulates the Metastasis of Canine Inflammatory Mammary Adenocarcinoma Cells Through Downregulation of Lysosomal Protective Protein Cathepsin A (CTSA)

Canine malignant mammary gland tumors present with a poor prognosis due to metastasis to other organs, such as lung and lymph node metastases. Unlike in human studies where obesity has been shown to increase the risk of breast cancer, this has not been well studied in veterinary science. In our preliminary study, we discovered that leptin downregulated cathepsin A, which is responsible for lysosomal-associated membrane protein 2a (LAMP2a) degradation. LAMP2a is a rate-limiting factor in chaperone-mediated autophagy and is highly active in malignant cancers. Therefore, in this study, alterations in metastatic capacity through cathepsin A by leptin, which are secreted at high levels in the blood of obese patients, were investigated. We used a canine inflammatory mammary gland adenocarcinoma (CHMp) cell line cultured with RPMI-1640 and 10% fetal bovine serum. The samples were then subjected to real-time polymerase chain reaction, Western blot, immunocytochemistry, and lysosome isolation to investigate and visualize the metastasis and chaperone-mediated autophagy-related proteins. Results showed that leptin downregulated cathepsin A expression at both transcript and protein levels, whereas LAMP2a, the rate-limiting factor of chaperone-mediated autophagy, was upregulated by inhibition of LAMP2a degradation. Furthermore, leptin promoted LAMP2a multimerization through the lysosomal mTORC2 (mTOR complex 2)/PH domain and leucine rich repeat protein phosphatase 1 (PHLPP1)/AKT1 (Serine/threonine-protein kinase 1) pathway. These findings suggest that targeting leptin receptors can alleviate mammary gland cancer cell metastasis in dogs.

Identification of oncolytic vaccinia restriction factors in canine high-grade mammary tumor cells using single-cell transcriptomics

Mammary carcinoma, including triple-negative breast carcinomas (TNBC) are tumor-types for which human and canine pathologies are closely related at the molecular level. The efficacy of an oncolytic vaccinia virus (VV) was compared in low-passage primary carcinoma cells from TNBC versus non-TNBC. Non-TNBC cells were 28 fold more sensitive to VV than TNBC cells in which VV replication is impaired. Single-cell RNA-seq performed on two different TNBC cell samples, infected or not with VV, highlighted three distinct populations: naïve cells, bystander cells, defined as cells exposed to the virus but not infected and infected cells. The transcriptomes of these three populations showed striking variations in the modulation of pathways regulated by cytokines and growth factors. We hypothesized that the pool of genes expressed in the bystander populations was enriched in antiviral genes. Bioinformatic analysis suggested that the reduced activity of the virus was associated with a higher mesenchymal status of the cells. In addition, we demonstrated experimentally that high expression of one gene, DDIT4, is detrimental to VV production. Considering that DDIT4 is associated with a poor prognosis in various cancers including TNBC, our data highlight DDIT4 as a candidate resistance marker for oncolytic poxvirus therapy. This information could be used to design new generations of oncolytic poxviruses. Beyond the field of gene therapy, this study demonstrates that single-cell transcriptomics can be used to identify cellular factors influencing viral replication.

The identification of cellular genes influencing viral replication/propagation has been studied using hypothesis-driven approaches and/or high-throughput RNA interference screens. In the present report, we propose a methodology based on single-cell transcriptomics. We have studied, in the context of oncolytic virotherapy, the susceptibility of different grades of primary low-passage mammary carcinoma cells of canine origin to an oncolytic vaccinia virus (VV). We highlight a fault in replication of VV in cells that originated from high-grade triple-negative breast carcinomas (TNBC). Single-cell RNA-seq performed on TNBC cell samples infected with VV suggested that the reduced activity of the virus was associated with a higher mesenchymal status of the cells. We also demonstrate that high expression of one gene, DDIT4, is detrimental to VV production. Considering that DDIT4 is associated with a poor prognosis in various cancers including TNBC, our data highlight DDIT4 as a candidate resistance marker for oncolytic poxvirus therapy. Beyond the field of cancer gene therapy, we demonstrate here that single-cell transcriptomics increases the arsenal of tools available to identify cellular factors influencing viral replication.

Intratumoral collagen signatures predict clinical outcomes in feline mammary carcinoma

Breast cancer is the most common cause of cancer-related deaths in women worldwide. Identification of reliable prognostic indicators and therapeutic targets is critical for improving patient outcome. Cancer in companion animals often strongly resembles human cancers and a comparative approach to identify prognostic markers can improve clinical care across species. Feline mammary tumors (FMT) serve as models for extremely aggressive triple negative breast cancer (TNBC) in humans, with high rates of local and distant recurrence after resection. Despite the aggressive clinical behavior of most FMT, current prognostic indicators are insufficient for accurately predicting outcome, similar to human patients. Given significant heterogeneity of mammary tumors, there has been a recent focus on identification of universal tumor-permissive stromal features that can predict biologic behavior and provide therapeutic targets to improve outcome. As in human and canine patients, collagen signatures appear to play a key role in directing mammary tumor behavior in feline patients. We find that patients bearing FMTs with denser collagen, as well as longer, thicker and straighter fibers and less identifiable tumor-stromal boundaries had poorer outcomes, independent of the clinical variables grade and surgical margins. Most importantly, including the collagen parameters increased the predictive power of the clinical model. Thus, our data suggest that similarities with respect to the stromal microenvironment between species may allow this model to predict outcome and develop novel therapeutic targets within the tumor stroma that would benefit both veterinary and human patients with aggressive mammary tumors.

Cross-species oncogenic signatures of breast cancer in canine mammary tumors

Genomic and precision medicine research has afforded notable advances in human cancer treatment, yet applicability to other species remains uncertain. Through whole-exome and transcriptome analyses of 191 spontaneous canine mammary tumors (CMTs) that exhibit the archetypal features of human breast cancers, we found a striking resemblance of genomic characteristics including frequent PIK3CA mutations (43.1%), aberrations of the PI3K-Akt pathway (61.7%), and key genes involved in cancer initiation and progression. We also identified three gene expression-based CMT subtypes, one of which segregated with basal-like human breast cancer subtypes with activated epithelial-to-mesenchymal transition, low claudin expression, and unfavorable disease prognosis. A relative lack of ERBB2 amplification and Her2-enrichment subtype in CMT denoted species-specific molecular mechanisms. Taken together, our results elucidate cross-species oncogenic signatures for a better understanding of universal and context-dependent mechanisms in breast cancer development and provide a basis for precision diagnostics and therapeutics for domestic dogs.

Arsenite and cadmium promote the development of mammary tumors

Previous studies demonstrate that the heavy metal cadmium and the metalloid arsenite activate estrogen receptor-alpha in breast cancer cells by forming a high-affinity complex with the ligand-binding domain of the receptor and that environmentally relevant doses of cadmium have estrogen-like activity in vivo. The present study showed that in estrogen-receptor positive cells, arsenite and cadmium increased the global expression of estrogen-responsive genes and that an environmentally relevant dose of arsenite also had estrogen-like activity in vivo. Similar to estrogens, exposure of ovariectomized animals to arsenite induced the expression of the progesterone receptor, GREB1, and c-fos in the mammary gland and the expression of complement C3, c-fos, and cyclin D1 in the uterus and the increase was blocked by the antiestrogen ICI-182,780. When virgin female animals were fed a diet, that mimics exposure to either arsenite or cadmium, and challenged with the chemical carcinogen dimethylbenzanthracene, there was an increase in the incidence of mammary tumors and a decrease in the time to tumor onset, but no difference in the total number of tumors, tumor multiplicity, or total tumor volume. Together with published results, these data showed that environmentally relevant amounts of arsenite and cadmium had estrogen-like activity in vivo and promoted mammary tumorigenesis.

Expression of estrogen receptor α variants and c-Fos in rat mammary gland and tumors

Breast cancer is currently the leading cause of cancer death among women worldwide. AP-1 (c-Fos/c-Jun) is associated with proliferation and survival, while cytoplasmic c-Fos activates phospholipid synthesis in cells induced to differentiate or grow. Estrogen receptor α 46 (ERα46) is a splice variant of full-length ERα66 and it is known that it has an inhibitory role in cancer cell growth. We investigated c-Fos localization, its relationship to AP-1, the non genomic pathway of phospho-Tyr537-ERα66, as well as ERα46 and ERα66 isoforms in rat mammary gland development and carcinogenic transformation, and in mammary tumors. Female rats were injected: a) saline solution (Control mammary gland, CMG) or b) N-Nitroso-N-methyl urea (NMU), and samples were taken at 60, 90, 120 and 150 days of life. In addition, we analyzed hormone-dependent (HD) and independent (HI) tumors in ovariectomized rats, and intact tumors (IT) in non-ovariectomized ones. Our results show that, in CMG, nuclear c-Fos and proliferation decreased with age, AP-1 content was low, and nuclear ERα46/ERα66 ratio was higher than 1. In NMU, nuclear c-Fos and proliferation increased with carcinogenic transformation, AP-1 content was high, and nuclear ERα46/ERα66 was below 1. As tumor grade increased, proliferation, nuclear c-Fos and AP-1 expression were negatively associated to nuclear ERα46/ERα66 in IT. In HD, nuclear ERα46/ERα66, nuclear c-Fos expression, AP-1 levels and proliferation were lower than in HI, whose growth is estrogen-independent. Phospho-Tyr537-ERα66 content and ERK1/2 activation were associated with AP-1 levels and cell proliferation. Collectively, our findings support the notion that variant detection and ERα46/ERα66 ratio could shed light on the role of ERα isoforms in mammary gland transformation and the behavior of ERα positive mammary tumors.

The Expression of Selected Factors Related to T Lymphocyte Activity in Canine Mammary Tumors

Crosstalk between neoplastic and immune cells in the tumor microenvironment (TME) influences the progression of disease in human and canine cancer patients. Given that canine mammary tumors are a useful model to study breast cancer biology, we aimed to evaluate the expression of genes associated with T lymphocyte activity in benign, malignant, and metastatic canine mammary tumors. Interestingly, metastatic tumors exhibit increased expression of CXCR3, CCR2, IL-4, IL-12p40, and IL-17. In particular, we focused on IL-17, a key interleukin associated with the Th17 lymphocyte phenotype. Th17 cells have been shown to play a contradictory role in tumor immunity. Although IL-17 showed a high expression in the metastatic tumors, the expression of RORγt, a crucial transcription factor for Th17 differentiation was barely detected. We further investigated IL-17 expression using immunohistochemistry, through which we confirmed the increased expression of this interleukin in malignant and metastatic mammary tumors. Finally, we compared the plasma levels of IL-17 in healthy and malignant mammary tumor-bearing dogs using ELISA but found no differences between the groups. Our data indicate that the IL-17 in metastatic tumors may be produced by other cell types, but not by Th17 lymphocytes. Overall, our results broaden the available knowledge on the interactions in canine mammary tumors and provide insight into the development of new therapeutic strategies, with potential benefits for human immune oncology.

Quantitative analysis of HER2 mRNA expression by RNA in situ hybridization in canine mammary gland tumors: Comparison with immunohistochemistry analysis

Spontaneously occurring canine mammary gland tumors share many features with human breast cancer, including biological behavior and histologic features. Compared to transgenic murine model, canine models have advantages including naturally occurring models of human diseases and cancer. In humans, breast cancer is divided into molecular subtypes based on ER, PR, and HER2 expression. In contrast with humans, few studies have evaluated these subtypes in canine mammary gland tumors, including expression of HER2. HER2 expression in canine mammary tissues has been further complicated by controversy regarding the antibody’s specificity. This study aimed to investigate c-erbB2 mRNA expression in retrospective formalin-fixed paraffin embedded samples, using RNA in situ hybridization with a novel quantitative assay and to compare this method with immunohistochemistry. Using 48 canine mammary tumor samples and 14 non-neoplastic canine mammary tissues, RNA in situ hybridization was performed with RNAscope^® using a canine-specific target gene probe (ERBB2), and quantitative measurement was performed using the housekeeping gene (POLR2A) to calculate the target gene/housekeeping gene ratio. The ratio of ERBB2/POLR2A was quantified using open-source image analysis programs and compared with the immunohistochemistry results. A significant correlation was observed between the HER2 immunohistochemistry score and ERBB2/POLR2A RNA in situ hybridization (P < 0.001). When the HER2 immunohistochemistry score was 3+, significantly higher expression of HER2 mRNA was observed by RNA in situ hybridization. Interestingly, HER2 mRNA was also observed in non-neoplastic mammary tissues by RNA in situ hybridization. This assay potentially facilitates the reliable quantification of mRNA expression levels in retrospective formalin-fixed paraffin-embedded samples. Further studies are required to elucidate the role of HER2 in canine mammary gland tumors and to implement clinical trials in dogs.

Establishment and Characterization of a Brca1-/-, p53-/- Mouse Mammary Tumor Cell Line

Breast cancer is the most commonly occurring cancer in women and the second most common cancer overall. By the age of 80, the estimated risk for breast cancer for women with germline BRCA1 or BRCA2 mutations is around 80%. Genetically engineered BRCA1-deficient mouse models offer a unique opportunity to study the pathogenesis and therapy of triple negative breast cancer. Here we present a newly established Brca1^−/−, p53^−/− mouse mammary tumor cell line, designated as CST. CST shows prominent features of BRCA1-mutated triple-negative breast cancers including increased motility, high proliferation rate, genome instability and sensitivity to platinum chemotherapy and PARP inhibitors (olaparib, veliparib, rucaparib and talazoparib). Genomic instability of CST cells was confirmed by whole genome sequencing, which also revealed the presence of COSMIC (Catalogue of Somatic Mutations in Cancer) mutation signatures 3 and 8 associated with homologous recombination (HR) deficiency. In vitro sensitivity of CST cells was tested against 11 chemotherapy agents. Tumors derived from orthotopically injected CST-mCherry cells in FVB-GFP mice showed sensitivity to cisplatin, providing a new model to study the cooperation of BRCA1-KO, mCherry-positive tumor cells and the GFP-expressing stromal compartment in therapy resistance and metastasis formation. In summary, we have established CST cells as a new model recapitulating major characteristics of BRCA1-negative breast cancers.

Prophylactic In Vivo Hematopoietic Stem Cell Gene Therapy with an Immune Checkpoint Inhibitor Reverses Tumor Growth in Syngeneic Mouse Tumor Models

Population-wide testing for cancer-associated mutations has established that more than one-fifth of ovarian and breast carcinomas are associated with inherited risk. Salpingo-oophorectomy and/or mastectomy are currently the only effective options offered to women with high-risk germline mutations. Our goal here is to develop a long-lasting approach that provides immunoprophylaxis for mutation carriers. Our approach leverages the fact that at early stages, tumors recruit hematopoietic stem/progenitor cells (HSPC) from the bone marrow and differentiate them into tumor-supporting cells. We developed a technically simple technology to genetically modify HSPCs in vivo. The technology involves HSPC mobilization and intravenous injection of an integrating HDAd5/35++ vector. In vivo HSPC transduction with a GFP-expressing vector and subsequent implantation of syngeneic tumor cells showed >80% GFP marking in tumor-infiltrating leukocytes. To control expression of transgenes, we developed a miRNA regulation system that is activated only when HSPCs are recruited to and differentiated by the tumor. We tested our approach using the immune checkpoint inhibitor anti-PD-L1-γ1 as an effector gene. In in vivo HSPC-transduced mice with implanted mouse mammary carcinoma (MMC) tumors, after initial tumor growth, tumors regressed and did not recur. Conventional treatment with an anti-PD-L1 mAb had no significant antitumor effect, indicating that early, self-activating expression of anti-PD-L1-γ1 can overcome the immunosuppressive environment in MMC tumors. The efficacy and safety of this approach was further validated in an ovarian cancer model with typical germline mutations (ID8 p53-/- brca2-/-), both in a prophylactic and therapeutic setting. This HSPC gene therapy approach has potential for clinical translation. SIGNIFICANCE: Considering the limited prophylactic options that are currently offered to women with high-risk germ-line mutations, the in vivo HSPC gene therapy approach is a promising strategy that addresses a major medical problem.

Analysis of Copy-Number Variations and Feline Mammary Carcinoma Survival

Feline mammary carcinomas (FMCs) are highly malignant. As the disease-free survival (DFS) and overall survival (OS) are short, prognostication is crucial. Copy-number variations (CNVs) analysis by next-generation sequencing serves to identify critical cancer-related genomic regions. Thirty-three female cats with FMCs were followed during two years after surgery. Tumours represented tubulopapillary and solid carcinomas encompassing six molecular subtypes. Regardless of the histopathological diagnosis, molecular subtypes showed important differences in survival. Luminal A tumours exhibited the highest DFS (p = 0.002) and cancer-specific OS (p = 0.001), and the lowest amount of CNVs (p = 0.0001). In contrast, basal-like triple-negative FMCs had the worst outcome (DFS, p < 0.0001; and OS, p < 0.00001) and were the most aberrant (p = 0.05). In the multivariate analysis, copy-number losses (CNLs) in chromosome B1 (1-23 Mb) harbouring several tumour-repressors (e.g. CSMD1, MTUS1, MSR1, DBC2, and TUSC3) negatively influenced DFS. Whereas, copy-number gains (CNGs) in B4 (1-29 Mb) and F2 (64-82.3 Mb) comprising epithelial to mesenchymal transition genes and metastasis-promoting transcription factors (e.g. GATA3, VIM, ZEB1, and MYC) negatively influenced DFS and cancer-specific OS. These data evidence an association between specific CNVs in chromosomes B1, B4 and F2, and poor prognosis in FMCs.

Cancer Cell-Derived Granulocyte-Macrophage Colony-Stimulating Factor Is Dispensable for the Progression of 4T1 Murine Breast Cancer

We previously reported that 4T1 murine breast cancer cells produce GM-CSF that up-regulates macrophage expression of several cancer promoting genes, including Mcp-1/Ccl2, Ccl17 and Rankl, suggesting a critical role of cancer cell-derived GM-CSF in cancer progression. Here, we attempted to define whether 4T1 cell-derived GM-CSF contributes to the expression of these genes by 4T1tumors, and their subsequent progression. Intraperitoneal injection of anti-GM-CSF neutralizing antibody did not decrease the expression of Mcp-1, Ccl17 or Rankl mRNA by 4T1 tumors. To further examine the role of cancer cell-derived GM-CSF, we generated GM-CSF-deficient 4T1 cells by using the Crisper-Cas9 system. As previously demonstrated, 4T1 cells are a mixture of cells and cloning of cells by itself significantly reduced tumor growth and lung metastasis. By contrast, GM-CSF-deficiency did not affect tumor growth, lung metastasis or the expression of these chemokine and cytokine genes in tumor tissues. By in-situ hybridization, the expression of Mcp-1 mRNA was detected in both F4/80-expressing and non-expressing cells in tumors of GM-CSF-deficient cells. These results indicate that cancer cell-derived GM-CSF is dispensable for the tuning of the 4T1 tumor microenvironment and the production of MCP-1, CCL17 or RANKL in the 4T1 tumor microenvironment is likely regulated by redundant mechanisms.

MicroRNA-710 regulates multiple pathways of carcinogenesis in murine metastatic breast cancer

Prior research has shown that critical differences between non-metastatic and metastatic tumor cells are at the level of microRNA. Consequently, harnessing these molecules for the treatment of metastatic cancer could have significant clinical impact. In the present study, we set out to identify metastasis-specific microRNAs which drive metastatic colonization of distant organs. Using a murine model of metastatic breast cancer, we employed a directed approach in which we screened for microRNAs that are differentially expressed between the primary tumors and metastatic lesions but concordantly expressed in all of the metastatic lesions irrespective of the tissue that is colonized. Of the identified targets, we focused on miR-710, which was consistently and significantly downregulated in the metastatic lesions relative to the primary tumors. The level of downregulation was independent of the distant organ that is involved, suggesting that miR-710 plays a fundamental role in metastatic colonization. Computational target prediction suggested a pleiotropic role for miR-710 in apoptosis, migration and invasion, and stemness. Using a previously validated oligonucleotide delivery system, we introduced miR-710 mimics into 4T1 metastatic breast adenocarcinoma cells and assessed the resultant phenotypic effects. We demonstrated significant inhibition of cell viability, migration, and invasion. We also showed that the treatment profoundly enhanced cell senescence, reduced stemness, and influenced markers of epithelial to mesenchymal transition, as evidenced by enhanced E-cadherin and reduced vimentin expression. This knowledge represents a first step towards harnessing a similar approach to discover novel microRNA targets with therapeutic potential in metastasis.

Exogenous ERα Expression in the Mammary Epithelium Decreases Over Time and Does Not Contribute to p53-Deficient Mammary Tumor Formation in Mice

Approximately 75% of all breast cancers express the nuclear hormone receptor estrogen receptor α (ERα). However, the majority of mammary tumors from genetically engineered mouse models (GEMMs) are ERα-negative. To model ERα-positive breast cancer in mice, we exogenously introduced expression of mouse and human ERα in an existing GEMM of p53-deficient breast cancer. After initial ERα expression during mammary gland development, expression was reduced or lost in adult glands and p53-deficient mammary tumors. Chromatin immunoprecipitation (ChIP)-sequencing analysis of primary mouse mammary epithelial cells (MMECs) derived from these models, in which expression of the ERα constructs was induced in vitro, confirmed interaction of ERα with the DNA. In human breast and endometrial cancer, and also in healthy breast tissue, DNA binding of ERα is facilitated by the pioneer factor FOXA1. Surprisingly, the ERα binding sites identified in primary MMECs, but also in mouse mammary gland and uterus, showed an high enrichment of ERE motifs, but were devoid of Forkhead motifs. Furthermore, exogenous introduction of FOXA1 and GATA3 in ERα-expressing MMECs was not sufficient to promote ERα-responsiveness of these cells. Together, this suggests that species-specific differences in pioneer factor usage between mouse and human are dictated by the DNA sequence, resulting in ERα-dependencies in mice that are not FOXA1 driven. These species-specific differences in ERα-biology may limit the utility of mice for in vivo modeling of ERα-positive breast cancer.

GATA3 Truncating Mutations Promote Cistromic Re-Programming In Vitro, but Not Mammary Tumor Formation in Mice

Heterozygous mutations in the transcription factor GATA3 are identified in 10-15% of all breast cancer cases. Most of these are protein-truncating mutations, concentrated within or downstream of the second GATA-type zinc-finger domain. Here, we investigated the functional consequences of expression of two truncated GATA3 mutants, in vitro in breast cancer cell lines and in vivo in the mouse mammary gland. We found that the truncated GATA3 mutants display altered DNA binding activity caused by preferred tethering through FOXA1. In addition, expression of the truncated GATA3 mutants reduces E-cadherin expression and promotes anchorage-independent growth in vitro. However, we could not identify any effects of truncated GATA3 expression on mammary gland development or mammary tumor formation in mice. Together, our results demonstrate that both truncated GATA3 mutants promote cistromic re-programming of GATA3 in vitro, but these mutants are not sufficient to induce tumor formation in mice.

Gene expression association study in feline mammary carcinomas

Works on cancer-related genes expression using feline mammary carcinomas (FMCs) are scarce but crucial, not only to validate these tumours as models for human breast cancer studies but also to improve small animal practice. Here, the expression of the cancer-related genes TP53, CCND1, FUS, YBX1, PTBP1, c-MYC and PKM2 was evaluated by real-time RT-qPCR, in a population of FMCs clinically characterized and compared with the disease-free tissue of the same individual. In most of the FMCs analysed, RNA quantification revealed normal expression levels for TP53, c-MYC, YBX1 and FUS, but overexpression in the genes CCND1, PTBP1 and PKM2. The expression levels of these cancer-related genes are strongly correlated with each other, with exception of c-MYC and PKM2 genes. The integration of clinicopathological data with the transcriptional levels revealed several associations. The oral contraceptive administration showed to be positively related with the TP53, YBX1, CCND1, FUS and PTBP1 RNA levels. Positive associations were found between tumour size and YBX1 RNA, and lymph node metastasis with c-MYC RNA levels. This work allowed to verify that many of these cancer-related genes are associated but may also, indirectly, influence other genes, creating a complex molecular cancer network that in the future can provide new cancer biomarkers.

Whole-exome and whole-transcriptome sequencing of canine mammary gland tumors

Studies of naturally occurring cancers in dogs, which share many genetic and environmental factors with humans, provide valuable information as a comparative model for studying the mechanisms of human cancer pathogenesis. While individual and small-scale studies of canine cancers are underway, more generalized multi-omics studies have not been attempted due to the lack of large-scale and well-controlled genomic data. Here, we produced reliable whole-exome and whole-transcriptome sequencing data of 197 canine mammary cancers and their matched controls, annotated with rich clinical and biological features. Our dataset provides useful reference points for comparative analysis with human cancers and for developing novel diagnostic and therapeutic technologies for cancers in pet dogs.

Mammary tumors compromise time-of-day differences in hypothalamic gene expression and circadian behavior and physiology in mice

Circadian rhythms influence various aspects of biology, including hormonal, immunological, and behavioral processes. These 24-hour oscillations are necessary to optimize cellular functions and to synchronize these processes with the environment. Breast cancer patients and survivors frequently report disruptions in circadian oscillations that adversely affect quality-of-life, including fragmented sleep-wake cycles and flattened cortisol rhythms, which are associated with negative behavioral comorbidities (e.g., fatigue). However, the potential causal role of tumor biology in circadian dysregulation has not been investigated. Here, we examined the extent to which sham surgery, non-metastatic mammary tumors, or mammary tumor removal in mice disrupts circadian rhythms in brain clock gene expression, locomotor behavior (free-running and entrained), and physiological rhythms that have been associated with cancer behavioral comorbidities. Tumors and tumor resection altered time-of-day differences in hypothalamic expression of eight circadian-regulated genes. The onset of activity in entrained running behavior was advanced in tumor-bearing mice, and the amplitude of free-running rhythms was increased in tumor-resected mice. Tumors flattened rhythms in circulating corticosterone and Ly6c^Hi monocytes which were largely restored by surgical tumor resection. This work implies that tumors alone may directly impact central and/or peripheral circadian rhythmicity in breast cancer patients, and that these effects may persist in cancer survivors, potentially contributing to behavioral comorbidities.