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The majority of clinical deaths in patients with triple-negative breast cancer (TNBC) are due to chemoresistance and aggressive metastases, with high prevalence in younger women of African ethnicity. Although tumorigenic drivers are numerous and varied, the drivers of metastatic transition remain largely unknown. Here, we uncovered a molecular dependence of TNBC tumors on the TRIM37 network, which enables tumor cells to resist chemotherapeutic as well as metastatic stress. TRIM37-directed histone H2A monoubiquitination enforces changes in DNA repair that rendered TP53-mutant TNBC cells resistant to chemotherapy. Chemotherapeutic drugs triggered a positive feedback loop via ATM/E2F1/ STAT signaling, amplifying the TRIM37 network in chemoresistant cancer cells. High expression of TRIM37 induced transcriptomic changes characteristic of a metastatic phenotype, and inhibition of TRIM37 substantially reduced the in vivo propensity of TNBC cells. Selective delivery of TRIM37-specific antisense oligonucleotides using antifolate receptor 1-conjugated nanoparticles in combination with chemotherapy suppressed lung metastasis in spontaneous metastatic murine models. Collectively, these findings establish TRIM37 as a clinically relevant target with opportunities for therapeutic intervention.Significance: TRIM37 drives aggressive TNBC biology by promoting resistance to chemotherapy and inducing a prometastatic transcriptional program; inhibition of TRIM37 increases chemotherapy efficacy and reduces metastasis risk in patients with TNBC.

Xylan is one of the major structural components of the plant cell wall. Xylan present in the human diet reaches the large intestine undigested and becomes a substrate to species of the gut microbiota. Here, we characterised the capacity of Limosilactobacillus reuteri and Blautia producta strains to utilise xylan derivatives. We showed that L. reuteri ATCC 53608 and B. producta ATCC 27340 produced β-D-xylosidases, enabling growth on xylooligosaccharide (XOS). The recombinant enzymes were highly active on artificial (p-nitrophenyl β-D-xylopyranoside) and natural (xylobiose, xylotriose, and xylotetraose) substrates, and showed transxylosylation activity and tolerance to xylose inhibition. The enzymes belong to glycoside hydrolase family 120 with Asp as nucleophile and Glu as proton donor, as shown by homology modelling and confirmed by site-directed mutagenesis. In silico analysis revealed that these enzymes were part of a gene cluster in L. reuteri but not in Blautia strains, and quantitative proteomics identified other enzymes and transporters involved in B. producta XOS utilisation. Based on these findings, we proposed a model for an XOS metabolism pathway in L. reuteri and B. producta strains. Together with phylogenetic analyses, the data also revealed the extended xylanolytic potential of the gut microbiota.

No abstract

Breast cancers are often evaluated by their expression of estrogen, progesterone and HER2/Neu receptors. Triple negative breast cancers (TNBC), which do not have upregulation of any of these receptors, lack directed therapies and therefore, are associated with a worse prognosis. The lack of directed therapies for TNBC and high incidence of relapse and drug resistance found in all breast cancers underscores the need for identification of additional therapeutic targets. The analysis of gene expression data revealed that PIM1 and PIM2 kinases are upregulated in triple negative breast cancer. PIM kinases are a family of serine/threonine kinases that activate cell division, promote cell growth, and inhibit apoptosis. Due to PIM1/2’s effect on these cellular processes and PIM1/2 being upregulated in TNBC, we hypothesized that PIM1/2 play an important role in progression of triple negative breast cancer. Knockdown of PIM1 significantly inhibited the proliferation, migration, and invasion of TNBC cells, including MDA-231, BT-20, HCC-1806, and MDA-468 cells. To study the in vivo roles of PIM1/2 in breast cancer progression and metastasis, we crossed the highly metastatic MMTV-PyMT breast cancer mouse model with PIM1/2 knockout mice. Deletion of PIM1 or PIM2 alone significantly inhibited tumor growth and reduced lung metastasis in these mice. Dual deletion of PIM1 and PIM2 significantly reduced tumor growth and almost completely blocked lung metastasis in these mice. A major advantage of the MMTV-PyMT model over xenograft models is that the immune system is intact in these mice, and that enabled us to perform immune cell profiling on the tumors. Tumor associated macrophages (TAMs) have been shown to promote tumor metastasis and are a poor prognostic marker for TNBC. Deletion of PIM1 alone and combined PIM1 and PIM2 deletion resulted in a significant reduction in the number of TAMs, indicating PIM1/2 play a significant role in regulating the immune milieu of these tumors. To understand the underlying mechanism by which PIM1 and PIM2 contribute to these processes, we performed biochemical analysis. Western blot analysis of PIM1 knockdown in MDA-231 cells showed a decrease in phosphorylation of CXCR4, S6 ribosomal protein, and 4EBP1 and increased expression of cell cycle regulator p27. Additionally, we performed RNA-seq analysis to identify which pathways were affected by PIM1/2 deletion in MMTV-PyMT tumors. GSEA analysis showed a significant enrichment of genes related to inflammatory response, extracellular matrix, EMT and metastasis in PyMT tumors and those were significantly reduced in PIM1/2 double knockout tumors. These results suggest that PIM1 and PIM2 play a significant role in the progression and metastasis of triple negative breast cancer and indicate that PIM1/2 inhibition could be a useful therapeutic approach for TNBC. Citation Format: Patrick Faughnan, Golam Mohi, Chandrajeet Singh. The roles of PIM1 and PIM2 kinases in the progression and metastasis of triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 149.