Endothelial follicle stimulating hormone receptor in primary kidney cancer correlates with subsequent response to sunitinib

Abstract

Sunitinib is an anti-angiogenic receptor tyrosine kinase inhibitor used to treat advanced metastatic renal cell carcinoma and other types of cancer. Sutent is effective in only approximately 70% of clear cell renal cell carcinoma (CCRCC) patients, has significant adverse side effects and no method is available to predict which patients will not respond. Our purpose was to explore the possibility of introducing an effective prediction method based on a marker of the tumour vasculature, the follicle stimulating hormone receptor (FSHR). Fifty patients diagnosed with advanced metastatic CCRCC have been subjected to surgery for removal of the primary tumour and were subsequently treated with sunitinib. After three months of therapy the patients were categorized as 'responsive', 'stable' or 'non-responsive' based on the RECIST guidelines. The blood vessel density and the percentage of FSHR-positive vessels were determined by immunofluorescence on sections from the primary tumours removed by surgery, prior to the sunitinib treatment. The percentage of FSHR-stained vessels was on average fivefold higher for the patients who responded to the treatment in comparison with the stable group and almost eightfold higher than in the non-responsive group. The percentage allowed the detection of responders with 87-100% sensitivity and specificity. No significant differences were detected in the total density of vessels among the three groups. The data suggest that FSHR expression levels in the blood vessels of CCRCC primary tumours can be used to predict, with high sensitivity and specificity, the patients who will respond to sunitinib therapy.

Fig 1

The CCRCC patients who respond to sunitinib treatment have a much higher density of FSHR-expressing vessels in the primary tumours, compared with patients who have stable disease or do not respond to the treatment. (A–C) Immunoperoxidase staining (red) for FSHR of paraffin sections from primary tumours removed by surgery. Representative images of tumour sections from responsive (A), stable (B) or non-responsive (C) patients. (D–L) Representative double immunofluorescence images of tumour sections used to determine the percentage of FSHR-positive vessels. Paraffin sections from primary tumours have been stained with antibodies against vWF and FSHR, followed by fluorescently labelled green and red, respectively, secondary antibodies. Tumour sections from patients responsive to sunitinib treatment (D–F), stable (G–I) or non-responsive (J–L). The arrows point to blood vessels. Bar: 20 μm.

Fig 2

The ratio between the density of the vessels that show a FSHR signal and vessels positive for von Willebrand factor (vWF) is correlated with the response of the patients to subsequent treatment with sunitinib. The bars correspond to 15 patients who responded to the treatment, 18 patients who were stable and 17 patients who did not respond. Errors bars: standard errors of the means computed for 20 microscopic fields for each patient. The three thick horizontal lines correspond to the averages for the three groups of patients (56.8 ± 5.4%, 11.4 ± 2% and 7.3 ± 0.7% for the responsive, stable and non-respective patients, respectively. The lines marked A and B correspond to the two thresholds (31% and 23%, respectively) used for the points A and B in Figure 3 to determine the sensitivities and the specificities of discriminating between the patients who are responsive versus the combined stable or non-responsive set.

Fig 3

The ratio of the density of FSHR-stained vessels divided by the density of vWF-stained vessels predicts with high sensitivity and selectivity the patients who will be responsive to sunitinib. Horizontal axis: sensitivity (%); vertical axis: specificity (%). For point A (for a threshold of the FSHR⁺/vWF⁺ stained vessels = 31%), the sensitivity is 87% and the specificity is 100% (i.e. 87% of the patients who will respond are correctly predicted, and none of the patients who will be stable or non-responsive are incorrectly predicted to be responsive); for point B (FSHR⁺/vWF⁺= 23%) the sensitivity is 100% and the specificity is 97% (dashed arrows) (i.e. all patients who will respond are correctly predicted, and only 3% of the stable or non-responsive patients are incorrectly predicted to be responsive).