Rapamycin synergizes with low-dose oxaliplatin in the HCT116 colon cancer cell line by inducing enhanced apoptosis

Abstract

Abstract. The present study aimed to examine the combined effects of oxaliplatin (L-OHP) and rapamycin (RAPA) in the HCT116 colon cancer cell line. The growth inhibitory effect was evaluated by MTT assay as a monotherapy or combination therapy. IC 50 values were determined using CalcuSyn 2.0 software. To determine the interaction of the drugs, the combination index (CI) was calculated using the Chou-Talalay method. Apoptosis was investigated using flow cytometry and Western blotting. Acridine orange staining was employed to observe morphological changes. The results showed the IC 50 values of L-OHP and RAPA to be 8.35±0.78 µM (r=0.99) and 223.44±38.10 nM (r=0.94), respectively. CI was ≤1 when L-OHP was used at doses ranging from 1 to 5 µM plus RAPA at a dose of 10 nM, suggesting synergistic or additive effects. CI was ≥1 when 100 nM RAPA was used in combination with low-dose L-OHP, showing additive to antagonistic effects. The combination of L-OHP (1 µM) and RAPA (10 nM) induced 19.76% Annexin V-positive cells, which was found to be higher than L-OHP (11.45%, p<0.01) or RAPA (6.89%, p<0.01) alone. The cleaved PARP protein expression levels were highest after 48 h of combination treatment. Acridine orange staining showed typical bright red Acidic vesicular organelles in the RAPA group, whereas the green condensed chromatin in the apoptotic bodies was found in both the L-OHP and combination groups. In conclusion, at a cytostatic concentration, RAPA was found to potentiate the anti-tumor effects of low-dose L-OHP in the HCT116 colon cancer cell by inducing enhanced apoptosis. IntroductionColorectal cancer (CRC) is the second most prevalent cancer and the third leading cause of cancer deaths worldwide (1). Oxaliplatin (L-OHP)-based chemotherapeutic regimens have proven to be effective in the prevention and treatment of tumor recurrence and metastasis in CRC. However, drug toxicity remains to be clarified in the clinic (2). Efforts have focused on incorporating cytotoxic and molecularly targeted agents into chemotherapy regimens to decrease toxicity and increase efficacy (3-5).The mammalian target of rapamycin (mTOR), an intracellular protein with a central role in the synthesis of key cellular proteins, has emerged as a significant target for anticancer therapy in various types of tumor. Phosphatidylinositol-3-kinase (PI3K)/Akt/mTOR pathway has been reported to be constitutively overexpressed in malignant tumors including CRC (6-7). Rapamycin (RAPA) is the special inhibitor of mTOR, which has demonstrated anti-tumor effects in a variety of malignancies in preclinical and clinical studies. In addition to being used as a monotherapy, RAPA and its analogs have been shown to enhance the efficacy of a number of cytotoxic chemotherapeutic agents in various types of cancer (8-11). Studies have shown that the anti-tumor mechanism of RAPA includes both apoptosis and autophagy, and its role in the fate of cancer cells remains controversial (12). The interaction between RAPA and L-OHP has yet to be clarified as the role of apo...

Antitumor Activity of Ruthenium(II) Terpyridine Complexes towards Colon Cancer Cells In Vitro and In Vivo

“…Ru-1 induced the arrest of CT26 and HCT116 cells in the G2/M phase, and Ru-2 caused G2/M phase arrest in SW480 cells, which is likely related to the molecular changes in the cancer cells ( Figure 7 ). Investigation of the effects of different treatment regimens on the apoptosis of CT26 and HCT116 cells demonstrated that oxaliplatin treatment appears to exhibit moderate effects on cell apoptosis, which is consistent with our research [ 26 , 34 , 35 ]. There are no in vitro alternative methods or their combinations which could fully replace in vivo methods for acute systemic toxicity [ 36 ].…”

Phosphorylated mTOR expression as a predictor of survival after liver resection for colorectal liver metastases

“…The patients who have a high p‐mTOR expression in liver metastases had poor prognoses after curative resection in the current study, indicating that those patients are likely candidates for chemotherapy and the mTOR pathway could be a pharmacological therapeutic target. Our data showed that the inhibition of p‐mTOR by rapamycin decreased the cellular proliferation of colorectal cancer cells in vitro, as reported previously 33 . However, everolimus monotherapy, a rapamycin analog, did not cause an objective tumor response for refractory colorectal cancer patients in a clinical study 28 .…”

A phase 1b study of OXIRI in pancreatic adenocarcinoma patients and its immunomodulatory effects

“…While metronomic oxaliplatin has not been widely explored thus far in pancreatic cancer, it has been shown to enhance overall cytotoxic effect in combination with chemotherapeutics in other GI cancers. 44,45 Oxaliplatin was found to significantly decrease VEGF levels in breast and gastric cancer cell lines when treated at two logarithmic dose levels below IC 50 . 46 In addition, when administered as part of a quadruplet regimen of nab-paclitaxel, leucovorin and bevacizumab, a refracted low oxaliplatin dose of 50 mg/m 2 was found to be tolerable with 25% of patients reporting grade 3 and higher neuropathy while displaying good clinical activity.…”

“…While metronomic oxaliplatin has not been widely explored thus far in pancreatic cancer, it has been shown to enhance overall cytotoxic effect in combination with chemotherapeutics in other GI cancers 44,45 . Oxaliplatin was found to significantly decrease VEGF levels in breast and gastric cancer cell lines when treated at two logarithmic dose levels below IC 50 46 .…”