Sorafenib augments cytotoxic effect of S-1 in vitro and in vivo through TS suppression

Efficacy and tolerability of Sorafenib plus metronomic chemotherapy S-1 for advanced hepatocellular carcinoma in preclinical and clinical assessments

OBJECTIVE

Although sorafenib, a molecular targeted agent, has survival benefits for advanced hepatocellular carcinoma (HCC) patients, its disease control rate remains limited. To explore the potential for augmenting its antitumor effect, we assessed the preclinical and clinical efficacy and tolerability of S-1 metronomic chemotherapy (MC) plus sorafenib.

METHODS

Antitumor effects and toxicity of this combination were tested with HAK-1B xenograft and spontaneous HCC mouse models, and a prospective pilot study was performed to compare therapeutic effects and safety between sorafenib plus MC S-1 for 12 advanced HCC cases and the historical control of 363 sorafenib-treated advanced HCC patients at our hospital from July 2011 to June 2015.

RESULTS

In mice, the combination chemotherapy enhanced anti-angiogenic effects, resulting in a stronger tumor hypoxic environment and increased tumor cell apoptosis. Clinically, the objective response rate of the combination chemotherapy was higher than that of sorafenib mono therapy (16.7%; 2/12 vs 5.2%; 19/363, p < 0.05); however, there were no significant differences in overall survival and time to progression. Adverse events including alopecia, thrombocytopenia, and pancreatic enzymes elevation in the combination chemotherapy were higher than those of sorafenib. No patient treated with the combination chemotherapy discontinued treatment due to severe adverse events.

CONCLUSIONS

Sorafenib plus MC S-1 seems to be effective and tolerable for patients with advanced HCC and could be considered a treatment option for these patients.

Effective Sequential Combined Chemotherapy with Trifluridine/Tipiracil and Regorafenib in Human Colorectal Cancer Cells

Salvage chemotherapy for refractory metastatic colorectal cancer using trifluridine/tipiracil (FTD/TPI) and regorafenib has shown survival benefits. We evaluated the antitumor effects of FTD or FTD/TPI combined with regorafenib in vitro and in vivo. SW620, HCT 116, and HT-29 human colorectal cancer cell lines were treated with FTD and regorafenib simultaneously and sequentially. Cell death, incorporation of FTD into DNA, and molecules related to FTD and regorafenib-associated cell death were investigated. The antitumor effects of FTD combined with regorafenib in SW620 and COLO205 xenografts were also evaluated. Cell death was greater after sequential treatment with FTD followed by regorafenib in SW620 cells, but not in HCT 116 and HT-29 cells, than after treatment with FTD alone, which was attributable to thymidylate synthase reduction with the induction of apoptosis. In contrast, simultaneous and sequential exposure to regorafenib followed by FTD, but not FTD alone, attenuated the cell death effect. Furthermore, combined FTD/TPI treatment followed by regorafenib had greater antitumor activity than either monotherapy in SW620 and COLO205 xenograft models. Treatment results following regorafenib administration subsequent to FTD or FTD/TPI suggest that sequential therapy with FTD/TPI prior to regorafenib may be effective in a clinical setting.

Dynamic PET evaluation of elevated FLT level after sorafenib treatment in mice bearing human renal cell carcinoma xenograft

Background

Sorafenib, an oral multikinase inhibitor, has anti-proliferative and anti-angiogenic activities and is therapeutically effective against renal cell carcinoma (RCC). Recently, we have evaluated the tumor responses to sorafenib treatment in a RCC xenograft using [Methyl-³H(N)]-3′-fluoro-3′-deoxythythymidine ([³H]FLT). Contrary to our expectation, the FLT level in the tumor significantly increased after the treatment. In this study, to clarify the reason for the elevated FLT level, dynamic 3′-[¹⁸F]fluoro-3′-deoxythymidine ([¹⁸F]FLT) positron emission tomography (PET) and kinetic studies were performed in mice bearing a RCC xenograft (A498).

The A498 xenograft was established in nude mice, and the mice were assigned to the control (n = 5) and treatment (n = 5) groups. The mice in the treatment group were orally given sorafenib (20 mg/kg/day p.o.) once daily for 3 days. Twenty-four hours after the treatment, dynamic [¹⁸F]FLT PET was performed by small-animal PET. Three-dimensional regions of interest (ROIs) were manually defined for the tumors. A three-compartment model fitting was carried out to estimate four rate constants using the time activity curve (TAC) in the tumor and the blood clearance rate of [¹⁸F]FLT.

Results

The dynamic pattern of [¹⁸F]FLT levels in the tumor significantly changed after the treatment. The rate constant of [¹⁸F]FLT phosphorylation (k₃) was significantly higher in the treatment group (0.111 ± 0.027 [1/min]) than in the control group (0.082 ± 0.009 [1/min]). No significant changes were observed in the distribution volume, the ratio of [¹⁸F]FLT forward transport (K₁) to reverse transport (k₂), between the two groups (0.556 ± 0.073 and 0.641 ± 0.052 [mL/g] in the control group).

Conclusions

Our dynamic PET studies indicated that the increase in FLT level may be caused by the phosphorylation of FLT in the tumor after the sorafenib treatment in the mice bearing a RCC xenograft. Dynamic PET studies with kinetic modeling could provide improved understanding of the biochemical processes involved in tumor responses to therapy.

Phase I/II study of S-1 in combination with sorafenib for metastatic renal cell carcinoma

BACKGROUND

The potential of S-1 for the treatment of metastatic renal cell carcinoma (mRCC) has been shown in two phase II studies. We aimed to assess the safety, tolerance, pharmacokinetics and clinical activity of S-1 combined with sorafenib in patients with mRCC.

PATIENTS AND METHODS

In this multicenter, single-arm, open-label, phase I/II study of S-1 plus sorafenib, we recruited patients with clear-cell or papillary renal cell carcinoma who had received a maximum of one prior cytokine-based regimen. The phase I primary end points were the maximum tolerated dose (MTD) and recommended dose (RD). S-1 was administered orally at 60, 80, 100 or 120 mg/day on days 1-28 of a 42-day cycle in combination with sorafenib (400 or 800 mg/day), given daily with dose adjustment. In phase II, the primary end point was to assess the overall response rate (ORR) at the RD.

RESULTS

Nine patients were enrolled into phase I and 21 (including 6 patients who received the RD in the phase I portion) were enrolled into phase II. In the phase I portion, the MTD could not be determined, and the RD was defined as S-1 80 mg/m(2)/day on days 1-28 + sorafenib 800 mg/day on days 1-42. In the phase II portion, 21 patients were fully assessable for efficacy and safety. The confirmed ORR was 52% [95% confidence interval (CI) 29.8-74.3], including one complete response (5%) and 10 partial responses (48%). The median progression-free survival was 9.9 (95% CI 6.5-17.1) months. The most frequently reported treatment-related adverse event for all grades was hand-foot skin reaction (100%). The major reasons for dose reduction were hand-foot skin reaction (38%) and rash (14%).

CONCLUSION

Combination therapy with S-1 plus sorafenib is effective and tolerable for patients with mRCC. However, skin events management is important in S-1 plus sorafenib combination therapy.

Final results of a phase II study of S-1 in patients with cytokine-refractory metastatic renal cell carcinoma

OBJECTIVE

A planned primary analysis of a Phase II study of S-1 demonstrated that the drug was active and tolerable in Japanese patients with cytokine-refractory metastatic renal cell carcinoma. Furthermore, pharmacogenomic analysis suggested that low expression of thymidylate synthase mRNA may have been associated with clinical outcome in terms of overall response rate and progression-free survival. Here, we report the results of the final analysis assessing the efficacy and safety of S-1 including overall survival.

METHODS

Patients with renal cell carcinoma were eligible if they had had at least one regimen of cytokine for metastatic disease. S-1 was orally administered on Days 1-28 of a 42-day cycle until disease progression. The primary endpoint was the overall response rate, and the secondary endpoint included progression-free survival, overall survival and safety.

RESULTS

A total of 45 patients were treated with S-1 and were fully assessable for efficacy and safety. At the final analysis, a response was seen in 11 patients (overall response rate, 24.4%; 95% confidence interval: 12.9-39.5%), including two patients who achieved a complete response. The final median progression-free and overall survival were 9.2 and 42.8 months, respectively. The safety profile of S-1 was favorable. It was suggested that there was no relation between overall survival and the expression level of thymidylate synthase.

CONCLUSION

This final analysis confirms that S-1 treatment is effective and safe in patients with cytokine-refractory renal cell carcinoma.

Increased intratumoral fluorothymidine uptake levels following multikinase inhibitor sorafenib treatment in a human renal cell carcinoma xenograft model

An early identification of the tumor response to sorafenib treatment is indispensable for selecting optimal personalized treatment strategies. However, at present, no reliable predictors are clinically available. ¹⁸F-fluorothymidine (¹⁸F-FLT) positron emission tomography (PET) is used to assess tumor proliferation, since the FLT uptake level reflects thymidine kinase-1 (TK-1) activity. Thus, the present study determined whether FLT was able to evaluate the early tumor response to sorafenib treatment in a human renal cell carcinoma (RCC; A498) xenograft in comparison with the tumor proliferation marker, Ki-67. Mice bearing A498 tumors were assigned to the control and sorafenib-treated groups and the tumor volume was measured every day. [Methyl-3H(N)]-3'-fluoro-3'-deoxythymidine (³H-FLT) was injected 2 h prior to the sacrifice of the mice on days three and seven following the treatment. ³H-FLT autoradiography (ARG) and Ki-67 immunohistochemistry (IHC) were performed using adjacent tumor sections. In the visual assessment, the intratumoral ³H-FLT uptake level diffusely increased following the treatment, while no significant changes were observed in Ki-67 IHC. The intratumoral ³H-FLT uptake levels significantly increased by 2.7- and 2.6-fold on days three and seven following the treatment, while the tumor volume and Ki-67 index did not significantly change. Thus, an increased FLT uptake level was demonstrated following the treatment, which may indicate the suppression of thymidylate synthase (TS) and the compensatory upregulation of TK-1 activity by sorafenib.

Vinorelbine and capecitabine in anthracycline- and/or taxane-pretreated metastatic breast cancer: sequential or combinational?

PURPOSE

The difference between combinational and pre-planned sequential therapies using regimens that include non-anthracycline and taxane in the first-line setting remains unclear. The purpose of this study is to explore the interaction between vinorelbine (N) and capecitabine (X) in breast cancer cells and to compare the simultaneous or sequential administration of the two drugs in patients with metastatic breast cancer (MBC) as first-line treatment.

METHODS

First, we explored the effects of vinorelbine on thymidine phosphorylase (TP) and thymidylate synthase (TS) expression in breast cancer cells. Next, we designed a prospective randomized phase II trial of MBC patients comparing the combinational and pre-planned sequential administration of vinorelbine and capecitabine in the first-line metastatic setting. The primary end point was progression-free survival (PFS). The correlation between clinical characteristics and class III β-tubulin expression and patient survival was also explored.

RESULTS

Vinorelbine upregulates TP and downregulates TS in breast cancer cells, thereby further sensitizing tumor cells to capecitabine, which indicated the proper order for sequential therapy should be N → X. Sixty patients were eligible for the phase II trial. No significant difference was observed between the combinational arm and the sequential arm in terms of progression-free survival (PFS), overall response rate (ORR), and overall survival (OS). Only in the subgroup of patients with liver metastases were median PFS and OS significantly prolonged in the combinational arm (8.5 vs. 6.4 months, P = 0.041 and 23.8 vs. 13.9 months, P = 0.028, respectively). No association between class III β-tubulin expression and patient outcome was identified. Grade 3/4 adverse events were more common in the combinational arm.

CONCLUSIONS

Both the NX regimen and pre-planned sequential N → X regimen are acceptable as first-line treatments with comparable efficacies for MBC patients previously treated with anthracyclines and/or taxanes. Sequential monotherapies are recommended as the preferred approach to first-line chemotherapy for most MBC patients in the absence of an imminent visceral crisis and the need for rapid symptom and/or disease control.

5-fluorouracil enhances the antitumor effect of sorafenib and sunitinib in a xenograft model of human renal cell carcinoma

Sorafenib and sunitinib are multi-kinase inhibitors with antitumor activity in patients with advanced renal cell carcinoma (RCC). Several studies have evaluated the effect of sorafenib/sunitinib in combination with chemotherapeutic agents in different types of tumor. However, few studies have addressed the activity of fluorinated pyrimidine in combination with sorafenib/sunitinib. In this study, we examined the potential of combination therapy with 5FU and sorafenib/sunitinib in human RCC cell lines. Three human RCC cell lines, ACHN, Caki-1 and Caki-2, were used to assess sensitivity to 5-fluorouracil (5FU), sorafenib and sunitinib alone or in combination using an in vitro cell survival assay. Caki-2 cells demonstrated significantly higher resistance to 5FU and sorafenib as compared to ACHN and Caki-1. Additive antitumor effects of the combination therapy were observed in the in vitro study. There was a tendency for a positive correlation between the sensitivity to sunitinib and platelet-derived growth factor β (PDGFR-β) expression levels, which were examined by reverse transcription polymerase chain reaction. Caki-1 xenograft models were prepared by inoculating cells subcutaneously into nude mice, which were divided randomly into six groups: control, 5FU (8 mg/kg/day, intraperitoneally), sorafenib (15 mg/kg/day, orally), sunitinib (20 mg/kg/day, orally), and 5FU with sorafenib or sunitinib. The treatments were administered on 5 days each week, and tumor growth was monitored for 42 days following inoculation of cells. Synergistic antitumor effects of the combination therapy were observed in an in vivo study. The resected tumors were evaluated using the Ki-67 labeling index and microvessel density. Both the Ki-67 labeling index and microvessel density were decreased in tumors treated with the combination therapy compared to those treated with sorafenib/sunitinib alone. These findings suggest that the combination therapy of 5FU with sorafenib/sunitinib may be an effective therapeutic modality for advanced RCC patients.

Combination therapy using oral S-1 and targeted agents against human tumor xenografts in nude mice

In this study, combination therapies using the oral fluoropyrimidine tegafur-gimeracil-oteracil (S-1) with several targeted agents or antibodies, were evaluated. First, the effects of tyrosine kinase inhibitors (erlotinib hydrochloride, sorafenib tosilate and sunitinib malate) against human non-small cell lung cancer (NSCLC), breast cancer and colorectal cancer were evaluated in vivo. The effects of the combination of S-1 and targeted antibodies (bevacizumab and cetuximab) against human colorectal cancers was also evaluated in vivo. S-1 and the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, erlotinib, showed a significant inhibition of growth in human NSCLC (Lu-99 and PC-9 cell lines). The antitumor activity of the combination of S-1 and erlotinib against Lu-99 and PC-9 cancer cell lines was significantly superior to either monotherapy (P<0.05). Combination therapy using the multi-tyrosine kinase inhibitors, sorafenib or sunitinib, with S-1 against breast cancer (MX-1 cell line) and NSCLC (NCI-H460 cell line) was significantly superior to either monotherapy (P<0.01). The combination of the anti-vascular endothelial growth factor antibody bevacizumab or the anti-EGFR antibody, cetuximab, with S-1 against human colorectal cancer [Col-1, KM20C (bevacizumab) and DLD-1 (cetuximab) cell lines] and a 5-fluorouracil (5-FU)-resistant cell line (KM12C/5-FU) was significantly superior to either monotherapy (p<0.01). In particular, the growth of the Col-1 cells was completely inhibited by the combination of S-1 and bevacizumab. No toxic mortalities and no significant difference in the body weight changes of the animals treated with S-1 combined with the targeted agents or with the mono-therapies were observed; therefore, the treatments appeared to be well-tolerated. Our preclinical findings indicate that the combination therapies of S-1 and targeted agents are promising treatment options.