PFKFB3 Inhibition Attenuates Oxaliplatin-Induced Autophagy and Enhances Its Cytotoxicity in Colon Cancer Cells

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3 (PFKFB3), a glycolytic enzyme highly expressed in cancer cells, has been reported to participate in regulating metabolism, angiogenesis, and autophagy. Although anti-cancer drug oxaliplatin (Oxa) effectively inhibits cell proliferation and induces apoptosis, the growing resistance and side-effects make it urgent to improve the therapeutic strategy of Oxa. Although Oxa induces the autophagy process, the role of PFKFB3 in this process remains unknown. In addition, whether PFKFB3 affects the cytotoxicity of Oxa has not been investigated. Here, we show that Oxa-inhibited cell proliferation and migration concomitant with the induction of apoptosis and autophagy in SW480 cells. Both inhibition of autophagy by small molecule inhibitors and siRNA modification decreased the cell viability loss and apoptosis induced by Oxa. Utilizing quantitative PCR and immunoblotting, we observed that Oxa increased PFKFB3 expression in a time- and dose-dependent manner. Meanwhile, suppression of PFKFB3 attenuated both the basal and Oxa-induced autophagy, by monitoring the autophagic flux and phosphorylated-Ulk1, which play essential roles in autophagy initiation. Moreover, PFKFB3 inhibition further inhibited the cell proliferation/migration, and cell viability decreased by Oxa. Collectively, the presented data demonstrated that PFKFB3 inhibition attenuated Oxa-induced autophagy and enhanced its cytotoxicity in colorectal cancer cells.

Chaperonin-containing tailless complex polypeptide 1 subunit 6A negatively regulates autophagy and protects colorectal cancer cells from cisplatin-induced cytotoxicity

BACKGROUND

As a member of the chaperonin-containing tailless complex polypeptide 1 (TCP1) complex, which plays a pivotal role in ensuring the accurate folding of numerous proteins, chaperonin-containing TCP1 subunit 6A (CCT6A) participates in various physiological and pathological processes. However, its effects on cell death and cancer therapy and the underlying mechanisms need further exploration in colorectal cancer (CRC) cells.

AIM

To explore the effects of CCT6A on cell death and cancer therapy and the underlying mechanisms in CRC.

METHODS

Cell proliferation was evaluated using the MTS assay, EdU staining, and colony growth assays. The expression of CCT6A was monitored by immunoblotting and quantitative PCR. CCT6A was knocked out by CRISPR-Cas9, and overexpressed by transfecting plasmids. Autophagy was examined by immunoblotting and the mCherry-GFP-LC3 assay. To monitor apoptosis and necroptosis, immunoblotting, co-immunoprecipitation, and flow cytometry were employed.

RESULTS

Cisplatin (DDP) exerted cytotoxic effects on CRC cells while simultaneously downregulating the expression of CCT6A. Depletion of CCT6A amplified the cytotoxic effects of DDP, whereas overexpression of CCT6A attenuated these adverse effects. CCT6A suppressed autophagy, apoptosis, and necroptosis under both basal and DDP-treated conditions. Autophagy inhibitors significantly enhanced the cytotoxic effects of DDP, whereas a necroptosis inhibitor partially reversed the cell viability loss induced by DDP. Furthermore, inhibiting autophagy enhanced both apoptosis and necroptosis induced by DDP.

CONCLUSION

CCT6A negatively modulates autophagy, apoptosis, and necroptosis, and CCT6A confers resistance to DDP therapy in CRC, suggesting its potential as a therapeutic target.

Necroptosis pathway blockage attenuates PFKFB3 inhibitor-induced cell viability loss and genome instability in colorectal cancer cells

Cancer cells prone to utilize aerobic glycolysis other than oxidative phosphorylation to sustain its continuous cell activity in the stress microenvironment. Meanwhile, cancer cells generally suffer from genome instability, and both radiotherapy and chemotherapy may arouse DNA strand break, a common phenotype of genome instability. Glycolytic enzyme PFKFB3 (6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3), plays essential roles in variety physiology and pathology processes, and generally maintain high level in cancer cells. Although this protein has been reported to involve in genome instability, its role remains unclear and controversial. Here, we showed that PFK-15, a PFKFB3 inhibitor, obviously induced apoptosis, cell viability loss, and inhibited cell proliferation/migration. Besides, PFK-15 was also found to induce necroptosis, as it not only up-regulated the phosphorylated RIP1, RIP3 and MLKL, but also enhanced the interaction between RIP3 and RIP1/MLKL, all of which are characterization of necroptosis induction. Both genetically and pharmacologically deprivation of necroptosis attenuated the cytotoxic effect of PFK-15. Besides, PFK-15 increased the γ-H2AX level and micronuclei formation, markers for genome instability, and inhibition of necroptosis attenuated these phenotypes. Collectively, the presented data demonstrated that PFK-15 induced genome instability and necroptosis, and deprivation of necroptosis attenuated cytotoxicity and genotoxicity of PFK-15 in colorectal cancer cells, thereby revealing a more intimate relationship among PFKFB3, necroptosis and genome instability.

SULT2B1: a novel therapeutic target in colorectal cancer via modulation of AKT/PKM2-mediated glycolysis and proliferation

BACKGROUND

Sulfotransferase family 2B member 1 (SULT2B1) is involved in regulating cell proliferation, migration and metabolism. However, there is still dispute regarding whether SULT2B1 acts as an oncogene or a suppressor, and the intrinsic mechanisms in modulating tumor progression need to be further elucidated.

METHODS

This work aims to reveal the relationship among SULT2B1, AKT, PKM2 signaling and glycolytic pathways, and provided a theoretical basis for SULT2B1 as a potential therapeutic target for CRC.Bioinformatics methods, immunohistochemistry (IHC) and immunoblotting assays were performed to analyze the correlation between SULT2B1 and colorectal cancer (CRC). The effect of SULT2B1 on cell proliferation and migration were investigated by several phenotypic experiments in vitro and animal studies. The SULT2B1 interacting proteins were determined by immunofluorescence, immunoprecipitation and GST-pull down assays. Immunoblotting and mCherry-GFP-LC3 assays were performed to analysis autophagy. Chromatin immunoprecipitation (CHIP) assay was utilized to detect the effect of SULT2B1 in regulating transcription. Small molecule agonist/antagonist was used to modify protein activity and therefore analyze the mutual relationships.

RESULTS

SULT2B1 is a predictive biomarker that is abnormally overexpressed in CRC tissues. Overexpression of SULT2B1 promoted cell proliferation and migration, while its knockout suppressed these processes. Furthermore, SULT2B1 could directly interact with the oncogene AKT and thereby enhance the activity of AKT-mTORC1 signaling. Furthermore, PKM2 was found to bind with SULT2B1, and regulated by SULT2B1 at both transcription and degradation levels. Moreover, blocking glycolysis attenuated the promoting effect of OE-SULT2B1.

CONCLUSION

SULT2B1 acts as an oncogene in CRC via modulating the AKT/PKM2 axis, therefore making it a promising diagnostic and therapeutic target for CRC.

CCT6A functions as promising diagnostic biomarker and promotes cell proliferation in colorectal cancer

Background: Chaperonin-containing tailless complex polypeptide 1 subunit 6A (CCT6A) is mainly located in the cytoplasm and considered to be involved in various biological processes in tumors. However, its function and the intrinsic mechanism need to be further elucidated. Methods: Multi-omics analysis was used to evaluate the correlation between CCT6A expression and prognosis of patients, as well as its immune value. CCT6A was knockout by CRISPR-Cas9, and overexpressed by transfecting plasmids in colorectal cancer (CRC) cells. Cell proliferation was analyzed by MTS, EDU staining and colony growth assay, and cell migration was monitored by wound healing assay and Transwell assay. The phosphor-kinase array kit and immunoblotting assay was utilized to explore the potential molecular mechanisms. Results: CCT6A was highly expressed in multiple tumor tissues and significantly correlated with the prognosis of patients. It was also associated with the immune infiltration, immune correlation and prognosis in CRC. CCT6A was highly expressed in CRC biopsies as well as fresh CRC tissues. Meanwhile, knockout of CCT6A reduced cell proliferation, cell cycle and cell migration. On the contrary, overexpression of CCT6A exhibited the opposite phenotypes. Moreover, we identified that HSPD1 and non-phosphorylated P53 were highly increased in CCT6A overexpressed cells, which are involved in regulating tumorigenesis. Conclusions: Therefore, CCT6A positively regulated cell proliferation/migration in CRC cells, and suggesting CCT6A has a high immunological value and is associated with CRC progression, which makes it a potential therapeutic target for CRC.

Impact of glycolysis enzymes and metabolites in regulating DNA damage repair in tumorigenesis and therapy

Initially, it was believed that glycolysis and DNA damage repair (DDR) were two distinct biological processes that independently regulate tumor progression. The former metabolic reprogramming rapidly generates energy and generous intermediate metabolites, supporting the synthetic metabolism and proliferation of tumor cells. While the DDR plays a pivotal role in preserving genomic stability, thus resisting cellular senescence and cell death under both physiological and radio-chemotherapy conditions. Recently, an increasing number of studies have shown closely correlation between these two biological processes, and then promoting tumor progression. For instance, lactic acid, the product of glycolysis, maintains an acidic tumor microenvironment that not only fosters cell proliferation and invasion but also facilitates DDR by enhancing AKT activity. Here, we provide a comprehensive overview of the enzymes and metabolites involved in glycolysis, along with the primary methods for DDR. Meanwhile, this review explores existing knowledge of glycolysis enzymes and metabolites in regulating DDR. Moreover, considering the significant roles of glycolysis and DDR in tumor development and radio-chemotherapy resistance, the present review discusses effective direct or indirect therapeutic strategies targeted to glycolysis and DDR.

PFKFB3 deprivation attenuates the cisplatin resistance via blocking its autophagic elimination in colorectal cancer cells

INTRODUCTION

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase isoform 3 (PFKFB3) is highly expressed in several cancers and plays important roles during the whole pathological process of cancer. It is also involved in chemoresistance, while the intrinsic mechanism needs to be further revealed.

METHODS

The different responses to cisplatin (DDP) between wild type (WT) and DDP-resistant (DDR) colorectal cancer (CRC) cells were analyzed by several assays. Coumarin conjugated DDP (CP-DDP) was utilized to trace the distribution of DDP. Pharmacological and genetic methods were used to deprive autophagy and PFKFB3, and the effects were investigated. The mouse xenograft model was performed to confirm the effect of the PFKFB3 inhibitor on reversing DDP resistance.

RESULTS

DDR cells showed a lower capacity for apoptosis upon DDP treatment, but exhibited higher levels of autophagy and PFKFB3. CP-DDP partly co-localized with LC3, and its content lessened faster in DDR cells. Deprivation of both autophagy and PFKFB3 attenuated CP-DDP elimination, and reversed the DDP resistance. Moreover, PFKFB3 inhibition reduced DDP-induced autophagy. PFKFB3 inhibitor in combination with DDP led to a remarkable reduction in tumor growth in vivo.

DISCUSSIONS

Inhibition of PFKFB3 reduced the autophagy induced by DDP, and therefore extended the retention time of CP-DDP. Meanwhile, PFKFB3 deprivation reversed the DDP resistance and made it a potent therapeutic target for CRC.