High Expression of Solute Carrier Family 2 Member 1 (SLC2A1) in Cancer Cells Is an Independent Unfavorable Prognostic Factor in Pediatric Malignant Peripheral Nerve Sheath Tumor

Abstract

Malignant peripheral nerve sheath tumor (MPNST) in children is a rare mesenchymal malignancy developing predominantly in the setting of neurofibromatosis type 1. The prognosis in advanced MPNST is poor therefore new prognostic markers are highly needed for optimal therapeutic decisions. In many solid tumors, the bidirectional interactions between hypoxia and inflammation in the tumor microenvironment via functions of tumor-associated cells, like neutrophils, lymphocytes and macrophages, have been investigated recently. There is no data whether in MPNST hypoxic microenvironment may translate into systemic inflammation, which is a well-established factor for worse prognosis in cancer patients. Therefore, we investigated the prognostic significance of markers of tumor hypoxia and systemic inflammation in 26 pediatric malignant peripheral nerve sheath tumors (MPNST). Tumor tissue microarrays were stained for hypoxia-inducible factor-1α (HIF1A), solute carrier family 2 member 1 (SLC2A1, also known as glucose transporter 1 (GLUT1)), carbonic anhydrase 9 (CA9), and vascular endothelial growth factor A (VEGFA) and classified into low- or high-expression groups. Baseline complete blood counts and C-reactive protein (CRP) levels were collected for all cases. Neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and lymphocyte-to-monocyte ratio (LMR) were calculated from age-adjusted complete blood count parameters. Both 10-year RFS and OS were significantly lower in patients with high NLR values (17% vs. 75%, p = 0.009, q = 0.018; and 31% vs. 100%, p = 0.0077, q = 0.014; respectively). Ten-year-OS was significantly lower in patients with high expression of SLC2A1 (20.00% vs. 94%, p < 0.001, log-rank), high expression of HIF1A (23% vs. 79%, p = 0.016, log-rank), and CRP higher than 31 mg/L (11% vs. 82%, p = 0.003, q = 0.009). Cox's proportional hazard regression analysis revealed that high expression of SLC2A1 (HR = 3.31, 95% CI = 1.08-10.09, p = 0.036) and VEGFA (HR = 4.40, 95% CI = 0.95-20.34, p = 0.058) were the independent factors predicting relapse, whereas high SLC2A1 was identified as the independent risk factor for death (HR = 12.20, 95% CI = 2.55-58.33, p = 0.002). Patients with high expression of hypoxic markers and low or high NLR/CRP values had the highest events rate, patients with low hypoxic markers and high NLR/CRP had intermediate events rate, while patients with low hypoxic markers and low NLR/CRP had the lowest events rate. SLC2A1 and VEGFA are promising novel prognostic factors in pediatric MPNST. Correlations between hypoxic and systemic inflammatory markers suggest the interplay between local tumor hypoxia and systemic inflammation.

Keywords: carbonic anhydrase 9; hypoxia-inducible factor-1α; lymphocyte-to-monocyte ratio; malignant peripheral nerve sheath tumor; markers of systemic inflammation; markers of tumor hypoxia; neutrophil-to-lymphocyte ratio; platelet-to-lymphocyte ratio; solute carrier family 2 member 1; vascular endothelial growth factor.

Figure 1

Immunohistochemical expression profile of hypoxic markers (SLC2A1, HIF1A, CA9, VEGFA) in the current cohort of MPNST. VEGFA was the most commonly highly expressed hypoxic marker, whereas SLC2A1 expression was low in most tumors (A). The vast majority of MPNSTs highly expressed at least one marker of hypoxia (B). Abbreviations: MPNST—malignant peripheral nerve sheath tumor, SLC2A1—solute carrier family 2 member 1, HIF1A—hypoxia-inducible factor-1α, CA9—carbonic anhydrase 9, VEGFA—vascular endothelial growth factor A.

Figure 2

(A–F) Representative SLC2A1 staining patterns in MPNSTs with the accompanying hematoxylin/eosin images: (A,B) A case with low-intensity (1+) membrane-cytoplasmic expression of SLC2A1 (the expression coefficient—7, low-expression). (C,D) Intermediate-intensity (2+) membranous staining intensity; (the expression coefficient—11, high-expression). (E,F) Predominantly strong (3+) to intermediate (2+) intensity membranous immunoreaction with SLC2A1 (the expression coefficient—12, high-expression). Abbreviations: SLC2A1—solute carrier family 2 member 1, MPNST—malignant peripheral nerve sheath tumor.

Figure 3

(A–D) Representative HIF1A staining patterns in MPNST: (A,B) Cases with absent (A) and low-intensity (1+) (B) nuclear expression of HIF1A (the expression coefficient—0, low-expression and 4, low-expression, respectively). (C,D) Cases with predominantly high-intensity (3+) nuclear (C) and nuclear/cytoplasmic (D) expression of HIF1A (the expression coefficient—12, high-expression in both cases). Abbreviations: HIF1A—hypoxia-inducible factor-1α, MPNST—malignant peripheral nerve sheath tumor.

Figure 4

(A–D) Representative VEGFA staining patterns in MPNST: (A,B) Cases with absent-to-very-low (A) and low-to-intermediate (1+/2+) (B) cytoplasmic expression of VEGFA (the expression coefficient—1, low-expression and 7, low-expression, respectively). (C,D) Cases with predominantly intermediate/high- (2+/3+) (C) and high-intensity (3+) (D) cytoplasmic expression of VEGFA (the expression coefficient—11, high-expression, and 12, high-expression, respectively). Abbreviations: VEGFA—vascular endothelial growth factor A, MPNST—malignant peripheral nerve sheath tumor.

Figure 5

(A–D) Representative CA9 staining patterns in MPNST: (A,B) Cases with low- (1+) (A) and intermediate-intensity (2+) (B) predominantly membranous expression of CA9 (the expression coefficient—7, low-expression and 8, high-expression, respectively). (C,D) Cases with predominantly intermediate/high (2+/3+) (C) and high intensity (3+) (D) membranous and cytoplasmic expression of CA9 (the expression coefficient—11, high-expression, and 12, high-expression, respectively). Abbreviations: CA9—carbonic anhydrase 9, MPNST—malignant peripheral nerve sheath tumor.

Figure 6

Receiver operating curves plotted for age-adjusted NLR, PLR, LMR, and LDH in pediatric patients with MPNST to predict events. Abbreviations: CRP—C-reactive protein, NLR—neutrophil-to-lymphocyte ratio, PLR—platelet-to-lymphocyte ratio, LMR—lymphocyte-to-monocyte ratio, LDH—lactate dehydrogenase.

Figure 7

Correlations between CRP and tumor size (A); NLR and tumor size (B); CRP and age (C); NLR and age (D). Abbreviations: CRP—C-reactive protein, NLR—neutrophil-to-lymphocyte ratio.

Figure 8

The associations between age-adjusted NLR and CRP levels and tumor location (A,B); and hypoxic markers (CA9, SLC2A1) expressions (C,D). Abbreviations: NLR—neutrophil-to-lymphocyte ratio, CRP—C-reactive protein, CA9—carbonic anhydrase 9, SLC2A1—solute carrier family 2 member 1.

Figure 9

Kaplan–Meier curves showing the probability of relapse-free survival grouped by SLC2A1 (A), HIF-1a (B), CA9 (C), VEGFA (D), NLR (E), and CRP (F). Abbreviations: SLC2A1—solute carrier family 2 member 1, HIF1A—hypoxia-inducible factor-1α, CA9—carbonic anhydrase 9, VEGFA—vascular endothelial growth factor A, NLR—neutrophil-to-lymphocyte ratio, CRP—C-reactive protein.

Figure 9

Kaplan–Meier curves showing the probability of relapse-free survival grouped by SLC2A1 (A), HIF-1a (B), CA9 (C), VEGFA (D), NLR (E), and CRP (F). Abbreviations: SLC2A1—solute carrier family 2 member 1, HIF1A—hypoxia-inducible factor-1α, CA9—carbonic anhydrase 9, VEGFA—vascular endothelial growth factor A, NLR—neutrophil-to-lymphocyte ratio, CRP—C-reactive protein.

Figure 10

Kaplan–Meier plots showing overall survival stratified by SLC2A1 (A), HIF1A (B), CA9 (C), VEGFA (D), NLR (E), CRP (F). Abbreviations: SLC2A1—solute carrier family 2 member 1, HIF1A—hypoxia-inducible factor-1α, CA9—carbonic anhydrase 9, VEGFA—vascular endothelial growth factor A, NLR—neutrophil-to-lymphocyte ratio, CRP—C-reactive protein.