Metformin revert insulin-induced oxaliplatin resistance by activating mitochondrial apoptosis pathway in human colon cancer HCT116 cells

Metabolic Alteration Bridging the Prediabetic State and Colorectal Cancer

Prediabetes and colorectal cancer (CRC) represent compelling health burdens responsible for high mortality and morbidity rates, sharing several modifiable risk factors. It has been hypothesized that metabolic abnormalities linking prediabetes and CRC are hyperglycemia, hyperinsulinemia, and adipokines imbalance. The chronic stimulation related to these metabolic signatures can favor CRC onset and development, as well as negatively influence CRC prognosis. To date, the growing burden of prediabetes and CRC has generated a global interest in defining their epidemiological and molecular relationships. Therefore, a deeper knowledge of the metabolic impairment determinants is compelling to identify the pathological mechanisms promoting the onset of prediabetes and CRC. In this scenario, this review aims to provide a comprehensive overview on the metabolic alterations of prediabetes and CRC as well as an overview of recent preventive and therapeutic approaches for both diseases, focusing on the role of the metabolic state as a pivotal contributor to consider for the development of future preventive and therapeutic strategies.

Metformin Increases the Response of Cholangiocarcinoma Cells to Gemcitabine by Suppressing Pyruvate Kinase M2 to Activate Mitochondrial Apoptosis

BACKGROUND

Cholangiocarcinoma (CCA) is a malignant tumor with a high mortality rate. Resistance to chemotherapy remains a major challenge related to cancer treatment, and increasing the sensitivity of cancer cells to therapeutic drugs is a major focus of cancer treatment.

AIMS

We purposed to explore the role of Metformin in CCA involved in chemotherapeutic sensitivity and Pyruvate kinase M2 (PKM2) through regulating mitochondrial apoptosis in the present study.

METHODS

CCA cell lines of HCC9810 and RBE were treated with Metformin companied with antagonists or agonists of PKM2, cells sensitivity to Gemcitabine, cell migration and invasion along with apoptosis, which is mediated by JC-1 and LDH were assayed.

RESULTS

Our results indicated that Metformin and Gemcitabine exhibit synergistic effect on inhibition of cholangiocarcinoma cell viability, cell migration and invasion as well as promotion apoptosis of cholangiocarcinoma cells. In vivo, Metformin combined with Gemcitabine has cooperation in inhibiting the growth of cholangiocarcinoma cell-derived tumors. Moreover, Metformin and Gemcitabine inhibited expression of PKM2 and PDHB in HCC9810 and RBE.

CONCLUSION

Our study suggested that Metformin may increase the response of cholangiocarcinoma cells to Gemcitabine by suppressing PKM2 to activate mitochondrial apoptosis.

Metformin alleviates adriamycin resistance of osteosarcoma by declining YY1 to inhibit MDR1 transcriptional activity

Chemotherapy resistance hinders the successful treatment of osteosarcoma (OS) to some extent. Previous studies have confirmed that metformin (Met) enhances apoptosis induced by chemotherapeutic drugs, but the underlying mechanism remains unclear. To establish adriamycin (ADM)-resistant MG-63 (MG-63/ADM) cells, the dosage of ADM was progressively increased. The results of qRT-PCR and Western blotting demonstrated that the expression level of Yin Yang 1 (YY1) and multi-drug resistance-1 (MDR1) in MG-63/ADM cells were remarkably increased compared with those in MG-63 cells. Met dramatically enhanced ADM cytotoxicity and accelerated apoptosis of MG-63/ADM cells. Moreover, Met suppressed the expressions of YY1 and MDR1 in MG-63/ADM cells. YY1 promoted its transcriptional expression by directly binding to the MDR1 promoter. Furthermore, the effects of Met on ADM sensitivity in MG-63/ADM cells was reversed due to overexpression of YY1 or MDR1. Collectively, these findings suggested that Met inhibited YY1/MDR1 pathway to reverse ADM resistance in OS, providing a new insight into the mechanism of Met in ADM resistance of OS.

Yinzhihuang injection induces apoptosis and suppresses tumor growth in acute myeloid leukemia cells

BACKGROUND

The unmet needs in treating acute myeloid leukemia(AML) promote us to look for more effective and less toxic therapies. In this study, we discovered that Yinzhihuang injection(YZHI), a traditional Chinese patent medicine for hepatitis treatment, suppressed the growth of AML cells.

METHOD

Anti-proliferative activities of YZHI were measured by CCK-8 assay. Cell cycle arrest was evaluated by PI staining, and apoptosis was evaluated by annexin V/PI staining. To explore the cell cycle arrest and cell death mechanism induced by YZHI, we assessed a series of assays, including measurements of the protein expression and cellular ATP. The anti-tumor activity was further demonstrated in nude mice.

RESULTS

Flow cytometric and biochemical analysis revealed that YZHI caused cell cycle arrest and induced apoptosis in the AML HL-60 cells. Mechanistically, YZHI activated AMPK by promoting phosphorylation of the kinase. The active AMPK negatively regulated the downstream target mTORC1, leading to the inhibition of cell proliferation and induction of apoptosis. Pretreatment with the AMPK inhibitor compound C rescued YZHI induced apoptosis and partially restored cell proliferation of HL-60. Consistent with the data in vitro, YZHI obviously suppressed subcutaneous xenograft growth in nude mice.

CONCLUSIONS

In a word, our data suggest that YZHI can be repurposed for the treatment of AML, which is worthy of further clinical evaluation.

Metformin is a metabolic modulator and radiosensitiser in rectal cancer

Resistance to neoadjuvant chemoradiation therapy, is a major challenge in the management of rectal cancer. Increasing evidence supports a role for altered energy metabolism in the resistance of tumours to anti-cancer therapy, suggesting that targeting tumour metabolism may have potential as a novel therapeutic strategy to boost treatment response. In this study, the impact of metformin on the radiosensitivity of colorectal cancer cells, and the potential mechanisms of action of metformin-mediated radiosensitisation were investigated. Metformin treatment was demonstrated to significantly radiosensitise both radiosensitive and radioresistant colorectal cancer cells in vitro. Transcriptomic and functional analysis demonstrated metformin-mediated alterations to energy metabolism, mitochondrial function, cell cycle distribution and progression, cell death and antioxidant levels in colorectal cancer cells. Using ex vivo models, metformin treatment significantly inhibited oxidative phosphorylation and glycolysis in treatment naïve rectal cancer biopsies, without affecting the real-time metabolic profile of non-cancer rectal tissue. Importantly, metformin treatment differentially altered the protein secretome of rectal cancer tissue when compared to non-cancer rectal tissue. Together these data highlight the potential utility of metformin as an anti-metabolic radiosensitiser in rectal cancer.

Metformin promotes cGAS/STING signaling pathway activation by blocking AKT phosphorylation in gastric cancer

The cGAS/STING signaling pathway plays a pivotal role in regulating innate immunity. Emerging novel drugs aim to regulate the anti-tumor immune response by activating innate immunity. The anti-diabetic drug metformin has been reported to exhibit anti-cancer effect against various types of cancer. However, the role of metformin in regulating the cGAS/STING signaling pathway in gastric cancer remains unknown. In our study, we first used bioinformatic analysis to detect that metformin is closely related to tumor immunity in multiple tumors. Next, we validated the function of metformin in activating the cGAS/STING signaling pathway in gastric cancer cell lines. In addition, KEGG pathway enrichment analysis showed that metformin is negatively correlated with the PI3K/AKT signaling pathway in gastric cancer. We further verified that metformin activates the cGAS/STING signaling pathway by blocking AKT phosphorylation. Moreover, we found that metformin regulates the AKT signaling pathway by mediating the transcription factor SOX2. Thus, our study indicates that metformin activates the cGAS/STING signaling pathway by suppressing SOX2/AKT and has promising potential in gastric cancer immunotherapy.

Macrophage-derived exosomes regulate gastric cancer cell oxaliplatin resistance by wrapping circ 0008253

Oxaliplatin (OXA) is a first-line chemotherapy drug for gastric cancer. We aimed to investigate the effect of circ 0008253, contained in M2 polarized macrophage-derived exosomes, on OXA resistance of gastric carcinoma cells. Flow cytometry was performed to detect the differentiation of macrophages and cell apoptosis. Cell Counting Kit-8 assay was conducted to examine the cell viability. Transmission electron microscopy, Nanoparticle Tracking Analysis, Western bolt, and Immunofluorescence were carried out. Cell proliferation was detected with a colony formation experiment. Levels of CD206, Arg1, IL-10, and TGF-β were increased in M2 polarized macrophages. Cell viability was decreased gradually with the increase of time and OXA concentration. Apoptosis of gastric carcinoma cells was decreased after co-culture with M2-polarized macrophages. Exosomes isolated from M2-polarized macrophages (M2-Exos) could be co-located with gastric carcinoma cells. M2-Exos enhanced drug resistance, reduced apoptosis and OXA resistance. Bioinformatics analysis showed that circ 0008253 could be transferred from M2-Exos to gastric carcinoma cells. Overexpressing circ 0008253 increased cell viability, tumor size, and ABCG2 levels, decreased OXA sensitivity. Circ 0008253, contained in M2-Exos, was directly transferred from tumor-associated macrophage to gastric carcinoma cells, finally enhancing OXA resistance.

LOXL2 reduces 5-FU sensitivity through the Hedgehog/BCL2 signaling pathway in colorectal cancer

Elevated expression of lysyl oxidase-like 2 (LOXL2) contributes to the malignant tumor progression in multiple cancers. However, the role of LOXL2 in the 5-fluorouracil (5-FU) resistance of colorectal cancer (CRC) remains unclear. This study aimed to explore the effects of LOXL2 on 5-FU sensitivity in CRC. The mRNA and protein levels of LOXL2 were explored in public databases by bioinformatics, validated in clinical tissues using immunohistochemistry, and detected in 5-FU treated cell lines. The 50% inhibitory concentrations (IC50) values were quantified based on the cell viability at different concentrations of 5-FU with CCK-8 assays. Colony formation and flow cytometry assays were performed to measure the proliferation and apoptosis rates. Gene set enrichment and correlation analyses were conducted to identify the probable mechanism of LOXL2 in TCGA samples. Critical molecules of the Hedgehog signaling pathway and anti-apoptotic BCL2 in protein levels were detected with Western blotting. It concluded that LOXL2 was up-regulated and positively linked to the unfavorable prognosis of CRC patients. The LOXL2 expression increased with the rising 5-FU concentrations, especially at 20 and 40 μM. Elevated LOXL2 promoted the resistance to 5-FU, augmented the proliferation, and inhibited 5-FU-induced apoptosis of CRC cells. LOXL2 activated the Hedgehog signaling pathway by promoting the expression of SMO, GLI1, and GLI2, leading to the upregulation of downstream target gene BCL2 in CRC cells. Moreover, the Hedgehog signaling pathway inhibitor cyclopamine blocked the BCL2 upregulation mediated by LOXL2. This study has demonstrated that LOXL2 can reduce 5-FU sensitivity through the Hedgehog/BCL2 signaling pathway in CRC.

Phosphoproteomic analysis of metformin signaling in colorectal cancer cells elucidates mechanism of action and potential therapeutic opportunities

BACKGROUND

The biguanide drug metformin is a safe and widely prescribed drug for type 2 diabetes. Interestingly, hundreds of clinical trials have been set to evaluate the potential role of metformin in the prevention and treatment of cancer including colorectal cancer (CRC). However, the "metformin signaling" remains controversial.

AIMS AND METHODS

To interrogate cell signaling induced by metformin in CRC and explore the druggability of the metformin-rewired phosphorylation network, we performed integrative analysis of phosphoproteomics, bioinformatics, and cell proliferation assays on a panel of 12 molecularly heterogeneous CRC cell lines. Using the high-resolute data-independent analysis mass spectrometry (DIA-MS), we monitored a total of 10,142 proteins and 56,080 phosphosites (P-sites) in CRC cells upon a short- and a long-term metformin treatment.

RESULTS AND CONCLUSIONS

We found that metformin tended to primarily remodel cell signaling in the long-term and only minimally regulated the total proteome expression levels. Strikingly, the phosphorylation signaling response to metformin was highly heterogeneous in the CRC panel, based on a network analysis inferring kinase/phosphatase activities and cell signaling reconstruction. A "MetScore" was determined to assign the metformin relevance of each P-site, revealing new and robust phosphorylation nodes and pathways in metformin signaling. Finally, we leveraged the metformin P-site signature to identify pharmacodynamic interactions and confirmed a number of candidate metformin-interacting drugs, including navitoclax, a BCL-2/BCL-xL inhibitor. Together, we provide a comprehensive phosphoproteomic resource to explore the metformin-induced cell signaling for potential cancer therapeutics. This resource can be accessed at https://yslproteomics.shinyapps.io/Metformin/.

Novel strategies to reverse chemoresistance in colorectal cancer

Colorectal cancer (CRC) is a common gastrointestinal malignancy with high morbidity and fatality. Chemotherapy, as traditional therapy for CRC, has exerted well antitumor effect and greatly improved the survival of CRC patients. Nevertheless, chemoresistance is one of the major problems during chemotherapy for CRC and significantly limits the efficacy of the treatment and influences the prognosis of patients. To overcome chemoresistance in CRC, many strategies are being investigated. Here, we review the common and novel measures to combat the resistance, including drug repurposing (nonsteroidal anti-inflammatory drugs, metformin, dichloroacetate, enalapril, ivermectin, bazedoxifene, melatonin, and S-adenosylmethionine), gene therapy (ribozymes, RNAi, CRISPR/Cas9, epigenetic therapy, antisense oligonucleotides, and noncoding RNAs), protein inhibitor (EFGR inhibitor, S1PR2 inhibitor, and DNA methyltransferase inhibitor), natural herbal compounds (polyphenols, terpenoids, quinones, alkaloids, and sterols), new drug delivery system (nanocarriers, liposomes, exosomes, and hydrogels), and combination therapy. These common or novel strategies for the reversal of chemoresistance promise to improve the treatment of CRC.

Irregular delay of adjuvant chemotherapy correlated with poor outcome in stage II-III colorectal cancer

AIMS

Adjuvant chemotherapy (ACT) plays an important role in improving the survival of stage II-III colorectal cancer (CRC) patients after curative surgery. However, the prognostic role of irregular delay of ACT (IDacT) for these patients has been less studied.

MATERIALS AND METHODS

A total of 117 stage II-III CRC patients who underwent radical resection and received at least 3 months ACT were enrolled retrospectively. The significance of IDacT, including total delay (TD) and delay per cycle (DpC), in predicting disease-free survival (DFS) was determined using receiver operating characteristic curve (ROC) analysis. The survival differences between the TD, DpC-short and DpC-long subgroups were tested using Kaplan-Meier analysis, and risk factors for prognosis were determined using a Cox proportional hazards model.

RESULTS

Using 35.50 and 3.27 days as the optimal cut-off points for TD and DpC, respectively, ROC analysis revealed that TD and DpC had sensitivities of 43.60% and 59.00% and specificities of 83.30% and 62.80%, respectively, in predicting DFS (both P < 0.05). No differences in the clinicopathological parameters were found between the TD, DpC-short or -long subgroups except histological differentiation in different TD subgroups and combined T stages in different DpC subgroups (both P = 0.04). Patients in the TD or DpC-long group exhibited significantly worse survival than in the -short group (TD: Log rank = 9.11, P < 0.01; DpC: Log rank = 6.09, P = 0.01). DpC was an independent risk factor for prognosis (HR = 2.54, 95% CI: 1.32-4.88, P = 0.01).

CONCLUSIONS

IDacT had a profound effect on the outcome for stage II-III CRC. Although TD and DpC were significant for the prognosis, DpC was more robust, and patients who presented DpC for a long time had a significantly worse DFS.

Luteolin Synergistically Enhances Antitumor Activity of Oxaliplatin in Colorectal Carcinoma via AMPK Inhibition

Luteolin is a naturally-occurring polyphenolic compound that is known to have antioxidative and antitumor activities in vitro. This study aimed to examine the in vivo anticancer efficacy of luteolin in conjunction with oxaliplatin treatment using a colorectal carcinoma xenograft mouse model. HCT116 human colorectal carcinoma cells were subcutaneously implanted into BALB/c nude mice, followed by the intraperitoneal administration of luteolin at a dose of 50 mg/kg body weight (BW)/day with or without oxaliplatin at a dose of 10 mg/kg BW/day three times per week for a total of 3 weeks. The combined luteolin and oxaliplatin treatment resulted in the synergistic suppression of the growth of HCT116 xenograft tumors when compared to treatment with luteolin or oxaliplatin alone. In addition, the combined treatment significantly increased the expression of cleaved PARP and p53 in the xenograft tumors compared with the vehicle control, but only marginally affected the level of heme oxygenase-1 (HO-1). These results indicated that luteolin treatment retarded oxaliplatin-induced tumor growth by facilitating apoptotic cell death and inhibiting HO-1-mediated cytoprotection. Therefore, these findings suggest the synergistic potential of dietary luteolin in conjunction with conventional chemotherapy for the treatment of colorectal cancer.

In Vivo and In Vitro Enhanced Tumoricidal Effects of Metformin, Active Vitamin D3, and 5-Fluorouracil Triple Therapy against Colon Cancer by Modulating the PI3K/Akt/PTEN/mTOR Network

Chemoresistance to 5-fluorouracil (5-FU) is common during colorectal cancer (CRC) treatment. This study measured the chemotherapeutic effects of 5-FU, active vitamin D3 (VD3), and/or metformin single/dual/triple regimens as complementary/alternative therapies. Ninety male mice were divided into: negative and positive (PC) controls, and 5-FU, VD3, Met, 5-FU/VD3, 5-FU/Met, VD3/Met, and 5-FU/VD3/Met groups. Treatments lasted four weeks following CRC induction by azoxymethane. Similar regimens were also applied in the SW480 and SW620 CRC cell lines. The PC mice had abundant tumours, markedly elevated proliferation markers (survivin/CCND1) and PI3K/Akt/mTOR, and reduced p21/PTEN/cytochrome C/caspase-3 and apoptosis. All therapies reduced tumour numbers, with 5-FU/VD3/Met being the most efficacious regimen. All protocols decreased cell proliferation markers, inhibited PI3K/Akt/mTOR molecules, and increased proapoptotic molecules with an apoptosis index, and 5-FU/VD3/Met revealed the strongest effects. In vitro, all therapies equally induced G1 phase arrest in SW480 cells, whereas metformin-alone showed maximal SW620 cell numbers in the G0/G1 phase. 5-FU/Met co-therapy also showed the highest apoptotic SW480 cell numbers (13%), whilst 5-FU/VD3/Met disclosed the lowest viable SW620 cell percentages (81%). Moreover, 5-FU/VD3/Met revealed maximal inhibitions of cell cycle inducers (CCND1/CCND3), cell survival (BCL2), and the PI3K/Akt/mTOR molecules alongside the highest expression of cell cycle inhibitors (p21/p27), proapoptotic markers (BAX/cytochrome C/caspase-3), and PTEN in both cell lines. In conclusion, metformin monotherapy was superior to VD3, whereas the 5-FU/Met protocol showed better anticancer effects relative to the other dual therapies. However, the 5-FU/VD3/Met approach displayed the best in vivo and in vitro tumoricidal effects related to cell cycle arrest and apoptosis, justifiably by enhanced modulations of the PI3K/PTEN/Akt/mTOR pathway.

ITGB4 as a novel serum diagnosis biomarker and potential therapeutic target for colorectal cancer

Purpose

To develop new and effective biomarkers for the diagnosis of colorectal cancer (CRC).

Experimental design

The serum expression of ITGB4 (49 CRC and 367 HC) was detected by enzyme‐linked immunosorbent assay (ELISA), and its diagnostic value was analyzed using the receiver operating characteristic (ROC) curve. The sensitivity and specificity of ITGB4 in CRC diagnosis were calculated through statistical analysis. The optimal clinical cutoff value was calculated using the Youden index, and diagnostic efficacy was analyzed in a larger serum sample (98 CRC and 1631 non‐CRC). The expression of ITGB4 was measured by CyTOF (cell experimental technology) at the single‐cell level, and characteristics were analyzed using viSNE and SPADE TREE.

Results

Serum ITGB4 and CEA levels were significantly higher in CRC patients than in HC and non‐CRC patients. The use of serum ITGB4 levels for the diagnosis of CRC has a high sensitivity (79%) but not high specificity when the clinical cutoff value was 0.70 ng/mL. However, the optimal cutoff value was 1.6 ng/mL with 86.2% specificity and 52.0% sensitivity, and the diagnostic efficacy was greatly improved with high specificity (82.0%) and sensitivity (71.4%) when combined with CEA. ITGB4 expression characteristics were measured and related to the expression of EpCAM, Ck8/18, and perforin at the single‐cell level. Single‐cell analysis showed that cell clusters with low expression of CK8/18 and ITGB4 were more sensitive to 5FU and radiotherapy (RT).

Conclusions

ITGB4 is an effective diagnostic serum biomarker and a potential therapeutic target for CRC.

Cytotoxicity of metformin against HT29 colon cancer cells contributes to mitochondrial Sirt3 upregulation

Cancer and diabetes, the two mitochondria-related diseases, have recently been linked to silent mating-type information regulation 2 homolog 3 (SIRT3) activity irregularities. In this study, the effect of metformin, an antidiabetic with anticancer properties, has been evaluated on mitochondrial functionality markers, cell death pathways, and SIRT3 enzyme activity in the colon cancer cell line, HT-29, and human embryonic kidney cells (HEK 293). HT-29 cells were treated with metformin (5, 10, 20, 40, and 80 µM) for 24, 48, and 72 h for measuring the IC₅₀ concentration. Reactive oxygen species (ROS) production, apoptosis, mitochondrial membrane potential, SIRT3 activity, and expression were evaluated against the colon cancer cell line, HT-29. Results indicated a higher ROS production at 6 than 12 h with metformin treatment. Metformin modified the mitochondrial membrane potential, resulting in cell death induction. Results from SIRT3 activity and expression showed that metformin increased its activity and expression in cancer cells. In conclusion, metformin in HT-29 cells disturbed the mitochondrial activity via increased ROS levels and SIRT3 activity, and these rapid modifications may play a key role in its cytotoxic property.

Clinical application and mechanism of traditional Chinese medicine in treatment of lung cancer

Lung cancer is a malignant tumor characterized by a rapid proliferation rate, less survivability, high mortality, and metastatic potential. This review focuses on updated research about the clinical application of traditional Chinese medicine (TCM) as an adjuvant therapy to lung cancer treatment and the mechanisms of TCM effect on lung cancer in vitro and in vivo. We summarized the recent 5 years of different research progress on clinical applications and antitumor mechanisms of TCM in the treatment of lung cancer. As a potent adjuvant therapy, TCM could enhance conventional treatments (chemotherapy, radiation therapy, and epidermal growth factor receptors [EGFRs] tyrosine kinase inhibitors [TKIs]) effects as well as provide synergistic effects, enhance chemotherapy drugs chemosensitivity, reverse drug resistance, reduce adverse reactions and toxicity, relieve patients’ pain and improve quality of life (QOL). After treating with TCM, lung cancer cells will induce apoptosis and/or autophagy, suppress metastasis, impact immune reaction, and therapeutic effect of EGFR-TKIs. Therefore, TCM is a promisingly potent adjuvant therapy in the treatment of lung cancer and its multiple mechanisms are worthy of an in-depth study.

Metformin revert insulin-induced oxaliplatin resistance by activating mitochondrial apoptosis pathway in human colon cancer HCT116 cells

BACKGROUND

Several studies have suggested that drug resistance in colon cancer patients with diabetes may be associated with long-term insulin administration, which in turn decreases the survival rate. Metformin is a commonly used drug to treat diabetes but has been recently demonstrated to have a potential therapeutic effect on colon cancer. This study aimed to elucidate the underlying mechanism by which metformin reverts insulin-induced oxaliplatin resistance in human colon cancer HCT116 cells.

METHODS

Two colon cancer cell lines (HCT116 and LoVo) were used to verify whether the expression of insulin receptor substrate 1 (IRS-1) could impact the half maximal inhibitory concentration (IC50) of oxaliplatin after chronic insulin treatment. The IC50 of oxaliplatin in both cell lines was measured to identify metformin sensitization to oxaliplatin. The adenosine monophosphate-activated protein kinase (AMPK) inhibitor, namely AMPK small interfering RNA, was used to block AMPK activation to identify critical proteins in the AMPK/Erk signaling pathway. Bcl-2 is a vital antiapoptotic protein involved in the mitochondrial apoptosis pathway. Finally, immunofluorescence and electron microscopy were performed to investigate how metformin affects the ultrastructural integrity of mitochondria.

RESULTS

The IC50 of oxaliplatin in HCT116 cells was noticeably increased. After the cells were treated with metformin, oxaliplatin resistance was reversed. According to the results of the western blotting assay of vital proteins involved in the classical apoptosis pathway, cleaved caspase-9 was noticeably upregulated, suggesting that the mitochondrial apoptosis pathway was activated. These results were verified by imaging of mitochondria using electron microscopy. The AMPK/Erk signaling pathway experiments revealed that the upregulation of Bcl-2 induced by insulin through Erk phosphorylation was inhibited by metformin and that such inhibition could be mitigated by the inhibition of AMPK.

CONCLUSIONS

Insulin-induced oxaliplatin resistance was reversed by metformin-mediated AMPK activation. Accordingly, metformin is likely to sensitize patients with diabetes to chemotherapeutic drugs used to treat colon cancer.