Captopril does not delay or alleviate proteinuria caused by apatinib and may counteract the anticancer efficacy of apatinib in HCC patients and tumor-bearing mouse models
Apatinib, a specific small molecule tyrosine kinase inhibitor (TKI), can highly selectively inhibit the tyrosine kinase activity of vascular endothelial growth factor receptor 2 (VEGFR-2). In China, apatinib has been recommended as second-line treatment of advanced gastric cancer and HCC[28-30]. From 2016 to the present, we used single-agent apatinib to treat 208 patients with advanced HCC. Apatinib exhibited a convincing anticancer effect and acceptable toxicity[31, 32]. We found that Captopril did not reduce the proteinuria caused by apatinib, and several patients even experienced deterioration. Patient 1 with severe advanced HCC received apatinib for 26 months and was in clinical, radiological and biological partial response when she developed severe hypertension and proteinuria. She was then administered captopril and experienced progression within the next 18 months. Alpha-fetoprotein (AFP) showed an upward trend throughout the entire captopril administration time and an occasional decrease because of the doubled dose of apatinib. The dose had to be reduced frequently because of intolerance. Captopril did not prevent the production of severe proteinuria caused by apatinib during the entire use process. Eventually, after the patient stopped using apatinib, the proteinuria level gradually decreased (Figure 1a). Patient 2 was also in radiological and biological partial response after 3 months of apatinib treatment. In the fourth month, she began taking captopril due to hypertension and proteinuria, and she then experienced progressive disease. After discontinuing captopril, the response to apatinib resumed (Supplemental Figure 1, a and c). The proteinuria was not alleviated by the use of captopril. Patient 3 had a partial response (PR) after 2 months of apatinib treatment. Subsequently, the patient was administered captopril at the same time due to proteinuria, and the disease progressed (Supplemental Figure 1, b).
Next, we subcutaneously injected MHCC-97H cells labeled with luciferase into the lateral forearm of BALB/c (nu/nu) male mice. Once tumors were established, the mice were given apatinib (200 mg/kg) daily, and the bioluminescence intensity of the mice was detected weekly. One week of apatinib administration decreased the luminescence signal by more than 60%, but the signal recovered after one week of supplementation with captopril (30 mg/kg/day) and decreased again after captopril was stopped for a week. The same trend was found in the next two dosing cycles (Figure 1b). These data suggest that ACEIs do not delay or reduce the proteinuria caused by AADs but rather may counteract the anti-angiogenic effect of AADs.
Determining the dose of drug used in the tumor-bearing mouse model and establishing a stable proteinuria model related to AADs
Because captopril was reported to promote tumor growth in an immunogenic model and decrease the survival of immunogenic mice in a dose-dependent manner[33], we established two mouse subcutaneous tumor models, the immunogenic C57BL/6 mouse model with Hep1-6 cells and the immunodeficient BALB/c nude mouse model with MHCC-97H cells to verify this effect. To generalize the role of ACEIs, we chose three representative drugs: captopril containing thiol, enalapril without thiol and fosinopril containing phosphorus[34]. After tumors were established (Figure 2, a and e), the mice received different doses of ACEIs [vehicle, high-dose captopril (60 mg/kg/day), low-dose captopril (30 mg/kg/day), high-dose enalapril (60 mg/kg/day), low-dose enalapril (30 mg/kg/day), high-dose fosinopril (10 mg/kg/day) and low-dose fosinopril (5 mg/kg/day)], which were based on the low and high doses used in humans according to a body surface area dose conversion method, as reported in previous literature[19, 35, 36]. The high dose was designed to be twice the low dose because the recommended dose of ACEIs for the treatment of proteinuria is twice that for the treatment of hypertension according to diabetic nephropathy guidelines[37, 38]. We observed that ACEIs decreased the survival of tumor-bearing immunogenic mice in a dose-dependent manner (Supplemental Figure 2a). However, in immunodeficient tumor-bearing mice, we found that only high-dose ACEIs reduced survival time, whereas low-dose ACEIs did not affect survival time (Supplemental Figure 2b). Regardless of immunogenic or immunodeficient tumor-bearing mice, high and low doses of ACEIs did not affect tumor growth (Supplemental Figure 2, c and d). These results prompted us to choose low-dose ACEIs in subsequent animal experiments.
The doses of apatinib in the treatment of tumor-bearing mice were 50 mg/kg/day, 100 mg/kg/day and 200 mg/kg/day according to the previous literature[39-41]. A comparison of the anticancer ability of different doses and whether various doses can lead to stable proteinuria have not been reported. Our results showed that in both liver cancer animal models, 200 mg/kg/day apatinib exhibited the best anticancer effect, prolonged the survival of tumor-bearing mice (Figure 2, b and f) and inhibited tumor growth (Figure 2, c and g). Importantly, the 200 mg/kg/day apatinib group produced stable proteinuria after two weeks (Figure 2, d and h). Targeting VEGF may cause two types of glomerular injury: thrombotic microangiopathy (TMA) and focal segmental glomerulopathy (FSGS) [42]. Both of them were observed in our apatinib-induced proteinuria mouse model (Figure 2i). These data confirmed that the optimal dose of apatinib was selected when studying the effect of apatinib on proteinuria.
Captopril does not reduce proteinuria or kidney damage caused by apatinib
In clinical practice, cancer patients may use ACEIs after the diagnosis of proteinuria caused by AADs. To fit the clinical situation, we administered apatinib to tumor-bearing mice for 2 weeks in advance to ensure stable proteinuria and then administered captopril to determine whether captopril could alleviate proteinuria (Figure 3a). From the initiation of captopril administration, the 24-hour urine of mice was collected via metabolic cages each week. From the weekly dynamic quantitative test and the qualitative test of the last week of captopril administration, the administration of captopril was not found to effectively alleviate albuminuria (Figure 3, b and c). Histological analysis of HE-stained, PAS-stained and Masson-stained kidney samples showed that captopril treatment neither attenuated the degree of glomerular injury nor reduced the proportion of damaged glomeruli (Figure 3, d and e). CD31 immunofluorescence staining of the kidneys showed a significant decrease in microblood vessels after apatinib treatment, which was not attenuated by captopril treatment (Figure 3f). Furthermore, captopril did not interfere with the effect of apatinib on the molecular level of the renal VEGF signaling pathway (Figure 3g). These data confirmed that captopril cannot reduce the proteinuria or kidney damage caused by apatinib.
ACEIs do not delay proteinuria or kidney damage caused by AADs
Although ACEIs have a definite effect on delaying proteinuria in diabetic nephropathy, ACEIs had no significant effect on the event of death[43]. Next, we sought to observe whether ACEIs could delay the appearance of proteinuria caused by AADs. We simultaneously administered different ACEIs and AADs to tumor-bearing mice (Figure 4a, Supplemental Figure 4a). Because Regorafenib has been shown to induce a higher rate of proteinuria when used to treat liver cancer[44], we selected apatinib and regorafenib as representatives of AADs, and we selected captopril, enalapril and fosinopril as representatives of ACEIs. Our data showed that although the combined use of ACEIs and AADs in the first three weeks resulted in lower quantified proteinuria than AADs alone, the difference was not statistically significant. After proteinuria was stabilized, proteinuria under treatment with ACEIs and AADs was almost the same as proteinuria induced by AADs alone (Figure 4b, Supplemental Figure 4c). Qualitative proteinuria in the urine of mice in the last week also confirmed that the combination of ACEIs could not reduce the proteinuria caused by AADs (Supplemental Figure 3a, Supplemental Figure 4b). Glomerular pathology analysis confirmed that the combination of ACEIs could not reduce the degree of glomerular damage or the proportion of damaged glomeruli caused by AADs (Supplemental Figure 3b, Figure 4c, Supplemental Figure 4, d and g). In view of the presence of glomeruli and renal hypertrophy in diabetic mice, we observed that neither AADs alone nor AADs combined with ACEIs caused hypertrophy or atrophy of the glomeruli and kidneys (Supplemental Figure 3, c and d, Supplemental Figure 4, e and f). Further experiments confirmed that ACEIs did not affect the inhibition of AADs on renal vascular and VEGF signaling pathways (Figure 4, d and e, Supplemental Figure 4h). Together, the above results indicated that ACEIs could not delay the occurrence of proteinuria end events caused by AADs.
ACEIs do not affect the reduction in proteinuria or the recovery of kidney injury after AAD withdrawal
As shown in Figure 1a, we found that after the use of AADs was stopped in patients, proteinuria gradually decreased and disappeared. Administration of the drugs was stopped after three weeks of treatment with apatinib and captopril, and the proteinuria of the mice was tested every week after administration (Figure 5a). We found that the proteinuria of the mice gradually disappeared after three weeks of apatinib withdrawal (Figure 5b). Pathological analysis of the kidneys revealed that glomerular damage was alleviated, and the proportion of damaged glomeruli was reduced from approximately 80% to 25% (Figure 4c and Figure 5d). Together, these results suggested that ACEIs do not delay or reduce the proteinuria caused by AADs. However, proteinuria gradually disappears, and kidney damage recovers after AAD withdrawal.
ACEIs reduce the anticancer efficacy of AADs, and their combined treatment promotes liver and lung metastasis in tumor-bearing mice with high metastatic potential
We tested three kinds of ACEIs and two kinds of AADs in two animal models to observe whether ACEIs could reduce the anticancer effect of AADs in different drug combinations. In tumor-bearing immunodeficient mice with MHCC-97H cells, we found that the use of low-dose ACEIs alone affected neither survival nor tumor growth. The combination of ACEIs and AADs inhibited tumor growth in tumor-bearing mice and improved survival. However, the improvement observed for the combined use was significantly lower than that observed for the use of AADs alone (Figure 6, a, b, d and e). We also measured the volume and mass of the tumors at specific time points. The combined use of ACEIs and AADs still corresponded to significantly higher tumor volume and mass than the use of AADs alone (Figure 6, c and f). We also observed liver and lung metastasis in mice. In the combined treatment group, some mice with subcutaneous tumors were found to have metastasis to the liver and lungs, in the ACEIs alone or AADs alone group, no liver or lung metastases were observed (Figure 6g).
In tumor-bearing immunogenic mice with Hep1-6 cells, low-dose ACEIs did not affect tumor growth or reduce the survival time. Although the combined use of ACEIs and AADs improved survival and inhibited tumor growth, the effects were significantly lower than those of AADs alone (Supplemental Figure 5). Consistent with the clinical observations shown in Figure 1 and Supplemental Figure 1, ACEIs did have an effect on reducing the anticancer efficacy of AADs, and the combined treatment of ACEIs and AADs may also promote the metastasis of cancer cells.
ACEIs reduce the anticancer efficacy of AADs by promoting the expression of kidney-derived EPO
In the process of exploring the mechanism by which ACEIs reduce the anticancer efficacy of AADs, a phenomenon that has attracted our attention, we noticed that the capillaries on the surface of the subcutaneous tumor were almost invisible in the nude mice treated with apatinib. However, after combined treatment with captopril, the capillaries on the surface of the tumor reappeared (Supplemental Figure 6a). We doubt whether the combined use of ACEIs reduces the anti-angiogenic efficacy of AADs. CD31 immunofluorescence staining revealed that, unlike in the kidney, ACEIs reduced the anti-angiogenesis effect of AADs in the tumor mass (Figure 7a, Supplemental Figure 6b). We further explored the effect on the VEGF signaling pathway in the tumor mass. As in the kidney, ACEIs did not interfere with the inhibition of VEGF signaling by AADs (Figure 7b, Supplemental Figure 6c). Because activation of the EPO signaling pathway has been well proven to be a main reason for the off-target anti-angiogenesis effect of AADs[21, 23], we analyzed the EPO signal of tumor tissues. The EPO and EphB4 protein levels in tumor tissues of the ACEI combination group were significantly higher than those of the AADs alone group (Figure 7c, Supplemental Figure 6d). The trend of EPO levels in the mouse serum was consistent with that in the tumor tissue (Figure 7d, Supplemental Figure 6e).
The liver, kidney, spleen and tumor are potential organs or tissues for EPO synthesis[21, 27]. Therefore, EPO mRNA was measured in these tissues, and no significant change was observed in the liver, spleen or tumor tissues. However, a significant increase in EPO mRNA was detected in the kidney in the ACEI combination group (Figure 7e, Supplemental Figure 6f). Western blotting and immunohistochemical staining further confirmed that the combination of ACEIs increased the levels of protein related to the EPO pathway to a greater degree than the use of AADs alone without affecting the VEGF signaling pathway (Figure 7f and 7g, Supplemental Figure 6g). These findings indicate that ACEIs aggravate the production of renal EPO caused by AADs, which leads to the rapid emergence of AAD resistance.