Increased expression of glutamine transporter SNAT2/SLC38A2 promotes glutamine dependence and oxidative stress resistance, and is associated with worse prognosis in triple-negative breast cancer.

BACKGROUND: Glutamine (Gln) is an abundant nutrient used by cancer cells. Breast cancers cells and particularly triple-receptor negative breast cancer (TNBC) are reported to be dependent on Gln to produce the energy required for survival and proliferation. Despite intense research on the role of the intracellular Gln pathway, few reports have focussed on Gln transporters in breast cancer and TNBC. METHODS: The role and localisation of the Gln transporter SLC38A2/SNAT2 in response to Gln deprivation or pharmacological stresses was examined in a panel of breast cancer cell lines. Subsequently, the effect of SLC38A2 knockdown in Gln-sensitive cell lines was analysed. The prognostic value of SLC38A2 in a cohort of breast cancer was determined by immunohistochemistry. RESULTS: SLC38A2 was identified as a strongly expressed amino acid transporter in six breast cancer cell lines. We confirmed an autophagic route of degradation for SLC38A2. SLC38A2 knockdown decreased Gln consumption, inhibited cell growth, induced autophagy and led to ROS production in a subgroup of Gln-sensitive cell lines. High expression of SLC38A2 protein was associated with poor breast cancer specific survival in a large cohort of patients (p = 0.004), particularly in TNBC (p = 0.02). CONCLUSIONS: These results position SLC38A2 as a selective target for inhibiting growth of Gln-dependent breast cancer cell lines.

SLC1A5 co-expression with TALDO1 associates with endocrine therapy failure in estrogen receptor-positive breast cancer.

PURPOSE: Identification of effective biomarkers for the benefit of endocrine treatment and understanding the molecular pathways that contribute to the development of resistance are of crucial importance to the management of luminal breast cancer. The amino acid transporter SLC1A5 has emerging importance as a prognostic marker and potential therapeutic target in various types of cancer. This study aims to investigate its role in luminal breast cancer as a potential predictive marker for endocrine treatment. METHODS: SLC1A5 expression was assessed at the transcriptomic and proteomic levels in large, well-characterized cohorts of luminal breast cancer. The sensitivity to endocrine therapy after SLC1A5 knockdown was investigated in vitro, using MCF7 and MDA-MB-175 cell lines. Bioinformatic analyses were performed to study the interacting networks of SLC1A5 and to identify a key co-expressed gene with SLC1A5. RESULTS: Here, we showed that patients with tumors that highly expressed SLC1A5 associated with a high risk of relapse after endocrine treatment. In vitro, depletion of SLC1A5 increases the sensitivity of luminal breast cancer cells to tamoxifen. TALDO1 was identified as key co-expressed gene with SLC1A5, and in vitro knockdown of SLC1A5 showed reduction in TALDO1 expression. Indeed, TALDO1 was associated with poor clinical outcomes in patients who were subject to endocrine therapy. CONCLUSION: These findings suggest that metabolic alterations, particularly the interaction between the key amino acid transporter SLC1A5 and metabolic enzyme TALDO1, could affect the sensitivity of endocrine therapy. This study demonstrated the prognostic value of both SLC1A5 and TALDO1 as biomarkers in luminal breast cancer.

Enhanced glutamine uptake influences composition of immune cell infiltrates in breast cancer.

BACKGROUND: Cancer cells must alter their metabolism to support proliferation. Immune evasion also plays a role in supporting tumour progression. This study aimed to find whether enhanced glutamine uptake in breast cancer (BC) can derive the existence of specific immune cell subtypes, including the subsequent impact on patient outcome. METHODS: SLC1A5, SLC7A5, SLC3A2 and immune cell markers CD3, CD8, FOXP3, CD20 and CD68, in addition to PD1 and PDL1, were assessed by using immunohistochemistry on TMAs constructed from a large BC cohort (n = 803). Patients were stratified based on SLC protein expression into accredited clusters and correlated with immune cell infiltrates and patient outcome. The effect of transient siRNA knockdown of SLC7A5 and SLC1A5 on PDL1 expression was evaluated in MDA-MB-231 cells. RESULTS: High SLCs were significantly associated with PDL1 and PD1 +, FOXP3 +, CD68 + and CD20 + cells (p < 0.001). Triple negative (TN), HER2 + and luminal B tumours showed variable associations between SLCs and immune cell types (p ≤ 0.04). The expression of SLCs and PDL1, PD1 +, FOXP3 + and CD68 + cells was associated with poor patient outcome (p < 0.001). Knockdown of SLC7A5 significantly reduced PDL1 expression. CONCLUSION: This study provides data that altered glutamine pathways in BC that appears to play a role in deriving specific subtypes of immune cell infiltrates, which either support or counteract its progression.

The solute carrier SLC7A8 is a marker of favourable prognosis in ER-positive low proliferative invasive breast cancer.

PURPOSE: Breast cancer (BC) is a heterogeneous disease consisting of various subtypes, with different prognostic and therapeutic outcomes. The amino acid transporter, SLC7A8, is overexpressed in oestrogen receptor-positive BC. However, the consequence of this overexpression, in terms of disease prognosis, is still obscure. This study aimed to evaluate the biological and prognostic value of SLC7A8 in BC with emphasis on the intrinsic molecular subtypes. METHODS: SLC7A8 was assessed at the genomic, using METABRIC data (n = 1980), and proteomic, using immunohistochemistry and TMA (n = 1562), levels in well-characterised primary BC cohorts. SLC7A8 expression was examined with clinicopathological parameters, molecular subtypes, and patient outcome. RESULTS: SLC7A8 mRNA and SLC7A8 protein expression were strongly associated with good prognostic features, including small tumour size, low tumour grade, and good Nottingham Prognostic Index (NPI) (all P < 0.05). Expression of SLC7A8 mRNA was higher in luminal tumours compared to other subtypes (P < 0.001). High expression of SLC7A8 mRNA and SLC7A8 protein was associated with good patient outcome (P ≤ 0.001) but only in the low proliferative ER+/luminal A tumours (P = 0.01). In multivariate analysis, SLC7A8 mRNA and SLC7A8 protein were independent factors for longer breast cancer specific survival (P = 0.01 and P = 0.03), respectively. CONCLUSION: SLC7A8 appears to play a role in BC and is a marker for favourable prognosis in the most predominant, ER+ low proliferative/luminal A, BC subtype. Functional assessment is necessary to reveal the specific role played by SLC7A8 in ER+ BC.

The role of glutaminase in cancer.

Increased glutamine metabolism (glutaminolysis) is a hallmark of cancer and is recognised as a key metabolic change in cancer cells. Breast cancer is a heterogeneous disease with different morphological and molecular subtypes and responses to therapy, and breast cancer cells are known to rewire glutamine metabolism to support survival and proliferation. Glutaminase isoenzymes (GLS and GLS2) are key enzymes for glutamine metabolism. Interestingly, GLS and GLS2 have contrasting functions in tumorigenesis. In this review, we explore the role of glutaminase in cancer, primarily focusing on breast cancer, address the role played by oncogenes and tumour suppressor genes in regulating glutaminase, and discuss current therapeutic approaches to targeting glutaminase.

PPFIA1 expression associates with poor response to endocrine treatment in luminal breast cancer.

BACKGROUND: PPFIA1 is an important regulator of cell migration and invasion, regulating focal adhesion signalling and disassembly. PPFIA1 is frequently amplified in breast cancer, and recent functional studies indicate that PPFIA1 is an important promoter of migration and invasion in breast cancer. This study aims to evaluate the utility of PPFIA1 expression in the luminal breast cancer as a prognostic marker to predict the response to endocrine therapy. METHODS: Large, well-characterised cohorts of primary luminal breast cancer patients with long-term follow-up was assessed for the clinical impact of PPFIA1 expression at the transcriptomic and proteomic levels. Prognostic significance of PPFIA1 and its relationship with clinical outcome and benefit of endocrine therapy were analysed. In addition, its association with other related-genes was analysed. RESULTS: There was significant association between PPFIA1 expression and a member of the liprin family that involves in cell invasion (PPFIBPI), and the cell cycle regulator (CCND1), whereas a negative association was observed with the tumour suppressor gene (CD82). Patients with high PPFIA1 expression were associated with high risk of recurrence, distant metastasis and death from breast cancer (P < 0.05). Importantly, high PPFIA1 expression predicted relapse in a subset of patients who were subject to endocrine treatment alone, and was an independent prognostic marker of unfavourable outcome in these patients (P < 0.05). CONCLUSIONS: These findings support the proposed role for PPFIA1 as a regulator of cell migration in breast cancer and provides definitive evidence for the clinical utility of PPFIA1 expression in patients with luminal breast cancer. Most importantly, our data suggests that PPFIA1 might be a potential predictive marker for poor benefit from endocrine therapy.

Co-Expression Effect of SLC7A5/SLC3A2 to Predict Response to Endocrine Therapy in Oestrogen-Receptor-Positive Breast Cancer.

The majority of breast cancers are oestrogen-receptor-positive (ER+) and are subject to endocrine therapy; however, an unpredictable subgroup of patients will develop resistance to endocrine therapy. The SLC7A5/SLC3A2 complex is a major route for the transport of large neutral essential amino acids through the plasma membrane. Alterations in the expression and function of those amino-acid transporters lead to metabolic reprogramming, which contributes to the tumorigenesis and drug resistance. This study aims to assess the effects and roles of SLC7A5/SLC3A2 co-expression in predicting responses to endocrine therapy in patients with ER+ breast cancer. The biological and clinical impact of SLC7A5/SLC3A2 co-expression was assessed in large annotated cohorts of ER+/HER2- breast cancer with long-term follow-up at the mRNA and protein levels. In vitro experiments were conducted to investigate the effect of SLC7A5/SLC3A2 knockdown in the proliferation of cancer cells and to the sensitivity to tamoxifen. We found that proliferation-related genes are highly expressed in a subgroup of patients with high SLC7A5/SLC3A2, and knockdown of SLC7A5/SLC3A2 decreased proliferation of ER+ breast cancer cells. In patients treated with endocrine therapy, high SLC7A5/SLC3A2 co-expression was associated with poor patient outcome, and depletion of SLC7A5/SLC3A2 using siRNA increased the sensitivity of breast cancer cells to tamoxifen. On the basis of our findings, SLC7A5/SLC3A2 co-expression has the potential of identifying a subgroup of ER+/HER2- breast cancer patients who fail to benefit from endocrine therapy and could guide the choice of other alternative therapies.

CDC20 expression in oestrogen receptor positive breast cancer predicts poor prognosis and lack of response to endocrine therapy.

PURPOSE: Endocrine therapy is the standard treatment for oestrogen receptor positive (ER+) breast cancer. Despite its efficacy, around half of patients will develop resistance to this treatment and eventually relapse. Identification of effective and reliable biomarkers to predict the efficacy of endocrine therapy is of crucial importance in the management of ER+ breast cancer. Emerging evidence has revealed that the cell division regulator CDC20 exhibits an oncogenic function and plays important roles in tumourigenesis and progression of solid tumours. In this study, we investigated the prognostic and predictive role of CDC20 in early ER+ breast cancer patients. METHODS: The biological and clinical impact of CDC20 expression was assessed in large clinical annotated cohort of ER+ breast cancer with long-term follow-up at the mRNA level, using METABRIC and KM-Plotter datasets, and the protein level using immunohistochemistry on patients presenting at Nottingham. CDC20 expression was correlated with clinico-pathological parameters, molecular subtypes, clinical outcome and efficacy of endocrine therapy. RESULTS: High CDC20 mRNA expression was associated with poor clinico-pathological parameters including large tumour size and high tumour grade (P < 0.0001) in patients with ER+ breast cancer. High CDC20 mRNA expression was significantly associated with poor patient outcome (P < 0.0001). Importantly, high CDC20 expression was correlated with poor response to endocrine treatment in patients who treated with hormonal therapy only (P < 0.01). In multivariate analysis, CDC20 mRNA was an independent predictor of poor clinical outcome after treatment with endocrine therapy (P = 0.02). CONCLUSION: CDC20 is a candidate biomarker for a subgroup of ER+ breast cancer characterised by poor clinical outcome. This study shows that the CDC20 could act as potential predictive biomarker of poor response to endocrine therapy in ER+ breast cancer.

The combined expression of solute carriers is associated with a poor prognosis in highly proliferative ER+ breast cancer.

PURPOSE: Breast cancer (BC) is a heterogeneous disease characterised by variant biology, metabolic activity, and patient outcome. Glutamine availability for growth and progression of BC is important in several BC subtypes. This study aimed to evaluate the biological and prognostic role of the combined expression of key glutamine transporters, SLC1A5, SLC7A5, and SLC3A2 in BC with emphasis on the intrinsic molecular subtypes. METHODS: SLC1A5, SLC7A5, and SLC3A2 were assessed at the protein level, using immunohistochemistry on tissue microarrays constructed from a large well-characterised BC cohort (n = 2248). Patients were stratified into accredited clusters based on protein expression and correlated with clinicopathological parameters, molecular subtypes, and patient outcome. RESULTS: Clustering analysis of SLC1A5, SLC7A5, and SLC3A2 identified three clusters low SLCs (SLC1A5-/SLC7A5-/SLC3A2-), high SLC1A5 (SLC1A5+/SLC7A5-/SLC3A2-), and high SLCs (SLC1A5+/SLC7A5+/SLC3A2+) which had distinct correlations to known prognostic factors and patient outcome (p < 0.001). The key regulator of tumour cell metabolism, c-MYC, was significantly expressed in tumours in the high SLC cluster (p < 0.001). When different BC subtypes were considered, the association with the poor outcome was observed in the ER+ high proliferation/luminal B class only (p = 0.003). In multivariate analysis, SLC clusters were independent risk factor for shorter BC-specific survival (p = 0.001). CONCLUSION: The co-operative expression of SLC1A5, SLC7A5, and SLC3A2 appears to play a role in the aggressive subclass of ER+ high proliferation/luminal BC, driven by c-MYC, and therefore have the potential to act as therapeutic targets, particularly in synergism.

Glutamate dehydrogenase (GLUD1) expression in breast cancer.

BACKGROUND: Dysregulated cellular metabolism is one of the hallmarks of cancer with some tumours utilising the glutamine metabolism pathway for their sustained proliferation and survival. Glutamate dehydrogenase (GLUD1) is a key enzyme in glutaminolysis converting glutamate to α-ketoglutarate for entry into the TCA cycle. Breast cancer (BC) comprises a heterogeneous group of tumours in terms of molecular biology and clinical behaviour, and we have previously shown that altered glutamine metabolism varies substantially among the different molecular subtypes. We hypothesise that the prognostic value of GLUD1 expression will differ between the BC molecular subtypes and may act as a potential therapeutic target for BC tumours. METHODS: GLUD1 was assessed at the DNA, mRNA (n = 1980) and protein (n = 1300) levels in large, well-characterised cohorts and correlated with clinicopathological parameters, molecular subtypes, patient outcome, and treatments. RESULTS: There was a correlation between GLUD1 mRNA and GLUD1 protein expression which were highly expressed in low grade luminal/ER + BC (p < 0.01). GLUD1 mRNA and protein was associated with good patient outcome but not in any specific molecular subtypes. However, high GLUD1 protein expression was associated with a better outcome in triple negative (TN) patients treated with chemotherapy (p = 0.03). High GLUD1 mRNA was associated with the glutamine transporter, SLC1A5, and leucine transporter, SLC7A8 as well as mTOR (p < 0.0001). CONCLUSION: We provide comprehensive data indicating GLUD1 plays an important role in luminal/ER + BC. GLUD1 expression predicts a better patient outcome and we show that it has the potential for predicting response to chemotherapy in TNBC patients.