Perifosine and ABT-737 synergistically inhibit lung cancer cells in vitro and in vivo

Anticancer drug response prediction integrating multi-omics pathway-based difference features and multiple deep learning techniques

Individualized prediction of cancer drug sensitivity is of vital importance in precision medicine. While numerous predictive methodologies for cancer drug response have been proposed, the precise prediction of an individual patient's response to drug and a thorough understanding of differences in drug responses among individuals continue to pose significant challenges. This study introduced a deep learning model PASO, which integrated transformer encoder, multi-scale convolutional networks and attention mechanisms to predict the sensitivity of cell lines to anticancer drugs, based on the omics data of cell lines and the SMILES representations of drug molecules. First, we use statistical methods to compute the differences in gene expression, gene mutation, and gene copy number variations between within and outside biological pathways, and utilized these pathway difference values as cell line features, combined with the drugs' SMILES chemical structure information as inputs to the model. Then the model integrates various deep learning technologies multi-scale convolutional networks and transformer encoder to extract the properties of drug molecules from different perspectives, while an attention network is devoted to learning complex interactions between the omics features of cell lines and the aforementioned properties of drug molecules. Finally, a multilayer perceptron (MLP) outputs the final predictions of drug response. Our model exhibits higher accuracy in predicting the sensitivity to anticancer drugs comparing with other methods proposed recently. It is found that PARP inhibitors, and Topoisomerase I inhibitors were particularly sensitive to SCLC when analyzing the drug response predictions for lung cancer cell lines. Additionally, the model is capable of highlighting biological pathways related to cancer and accurately capturing critical parts of the drug's chemical structure. We also validated the model's clinical utility using clinical data from The Cancer Genome Atlas. In summary, the PASO model suggests potential as a robust support in individualized cancer treatment. Our methods are implemented in Python and are freely available from GitHub (https://github.com/queryang/PASO).

Combined BCL-2 and PI3K/AKT Pathway Inhibition in KMT2A-Rearranged Acute B-Lymphoblastic Leukemia Cells

Numerous hematologic neoplasms, including acute B-lymphoblastic leukemia (B-ALL), are characterized by overexpression of anti-apoptotic BCL-2 family proteins. Despite the high clinical efficacy of the specific BCL-2 inhibitor venetoclax in acute myeloid leukemia (AML) and chronic lymphocytic leukemia (CLL), dose limitation and resistance argue for the early exploration of rational combination strategies. Recent data indicated that BCL-2 inhibition in B-ALL with KMT2A rearrangements is a promising intervention option; however, combinatorial approaches have not been in focus so far. The PI3K/AKT pathway has emerged as a possible target structure due to multiple interactions with the apoptosis cascade as well as relevant dysregulation in B-ALL. Herein, we demonstrate for the first time that combined BCL-2 and PI3K/AKT inhibition has synergistic anti-proliferative effects on B-ALL cell lines. Of note, all tested combinations (venetoclax + PI3K inhibitors idelalisib or BKM-120, as well as AKT inhibitors MK-2206 or perifosine) achieved comparable anti-leukemic effects. In a detailed analysis of apoptotic processes, among the PI3K/AKT inhibitors only perifosine resulted in an increased rate of apoptotic cells. Furthermore, the combination of venetoclax and perifosine synergistically enhanced the activity of the intrinsic apoptosis pathway. Subsequent gene expression studies identified the pro-apoptotic gene BBC3 as a possible player in synergistic action. All combinatorial approaches additionally modulated extrinsic apoptosis pathway genes. The present study provides rational combination strategies involving selective BCL-2 and PI3K/AKT inhibition in B-ALL cell lines. Furthermore, we identified a potential mechanistic background of the synergistic activity of combined venetoclax and perifosine application.

Synergistic cytotoxicity of perifosine and ABT-737 to colon cancer cells

An acidic environment and hypoxia within the tumour are hallmarks of cancer that contribute to cell resistance to therapy. Deregulation of the PI3K/Akt pathway is common in colon cancer. Numerous Akt-targeted therapies are being developed, the activity of Akt-inhibitors is, however, strongly pH-dependent. Combination therapy thus represents an opportunity to increase their efficacy. In this study, the cytotoxicity of the Akt inhibitor perifosine and the Bcl-2/Bcl-xL inhibitor ABT-737 was tested in colon cancer HT-29 and HCT-116 cells cultured in monolayer or in the form of spheroids. The efficacy of single drugs and their combination was analysed in different tumour-specific environments including acidosis and hypoxia using a series of viability assays. Changes in protein content and distribution were determined by immunoblotting and a "peeling analysis" of immunohistochemical signals. While the cytotoxicity of single agents was influenced by the tumour-specific microenvironment, perifosine and ABT-737 in combination synergistically induced apoptosis in cells cultured in both 2D and 3D independently on pH and oxygen level. Thus, the combined therapy of perifosine and ABT-737 could be considered as a potential treatment strategy for colon cancer.

BH3-mimetics: recent developments in cancer therapy

The hopeful outcomes from 30 years of research in BH3-mimetics have indeed served a number of solid paradigms for targeting intermediates from the apoptosis pathway in a variety of diseased states. Not only have such rational approaches in drug design yielded several key therapeutics, such outputs have also offered insights into the integrated mechanistic aspects of basic and clinical research at the genetics level for the future. In no other area of medical research have the effects of such work been felt, than in cancer research, through targeting the BAX-Bcl-2 protein-protein interactions. With these promising outputs in mind, several mimetics, and their potential therapeutic applications, have also been developed for several other pathological conditions, such as cardiovascular disease and tissue fibrosis, thus highlighting the universal importance of the intrinsic arm of the apoptosis pathway and its input to general tissue homeostasis. Considering such recent developments, and in a field that has generated so much scientific interest, we take stock of how the broadening area of BH3-mimetics has developed and diversified, with a focus on their uses in single and combined cancer treatment regimens and recently explored therapeutic delivery methods that may aid the development of future therapeutics of this nature.

Lactic Acidosis Interferes With Toxicity of Perifosine to Colorectal Cancer Spheroids: Multimodal Imaging Analysis

Colorectal cancer (CRC) is a disease with constantly increasing incidence and high mortality. The treatment efficacy could be curtailed by drug resistance resulting from poor drug penetration into tumor tissue and the tumor-specific microenvironment, such as hypoxia and acidosis. Furthermore, CRC tumors can be exposed to different pH depending on the position in the intestinal tract. CRC tumors often share upregulation of the Akt signaling pathway. In this study, we investigated the role of external pH in control of cytotoxicity of perifosine, the Akt signaling pathway inhibitor, to CRC cells using 2D and 3D tumor models. In 3D settings, we employed an innovative strategy for simultaneous detection of spatial drug distribution and biological markers of proliferation/apoptosis using a combination of mass spectrometry imaging and immunohistochemistry. In 3D conditions, low and heterogeneous penetration of perifosine into the inner parts of the spheroids was observed. The depth of penetration depended on the treatment duration but not on the external pH. However, pH alteration in the tumor microenvironment affected the distribution of proliferation- and apoptosis-specific markers in the perifosine-treated spheroid. Accurate co-registration of perifosine distribution and biological response in the same spheroid section revealed dynamic changes in apoptotic and proliferative markers occurring not only in the perifosine-exposed cells, but also in the perifosine-free regions. Cytotoxicity of perifosine to both 2D and 3D cultures decreased in an acidic environment below pH 6.7. External pH affects cytotoxicity of the other Akt inhibitor, MK-2206, in a similar way. Our innovative approach for accurate determination of drug efficiency in 3D tumor tissue revealed that cytotoxicity of Akt inhibitors to CRC cells is strongly dependent on pH of the tumor microenvironment. Therefore, the effect of pH should be considered during the design and pre-clinical/clinical testing of the Akt-targeted cancer therapy.

Randomized, placebo-controlled, phase 3 study of perifosine combined with bortezomib and dexamethasone in patients with relapsed, refractory multiple myeloma previously treated with bortezomib

Perifosine, an investigational, oral, synthetic alkylphospholipid, inhibits signal transduction pathways of relevance in multiple myeloma (MM) including PI3K/Akt. Perifosine demonstrated anti-MM activity in preclinical studies and encouraging early-phase clinical activity in combination with bortezomib. A randomized, double-blind, placebo-controlled phase 3 study was conducted to evaluate addition of perifosine to bortezomib-dexamethasone in MM patients with one to four prior therapies who had relapsed following previous bortezomib-based therapy. The primary endpoint was progression-free survival (PFS). The study was discontinued at planned interim analysis, with 135 patients enrolled. Median PFS was 22.7 weeks (95% confidence interval 16·0-45·4) in the perifosine arm and 39.0 weeks (18.3-50.1) in the placebo arm (hazard ratio 1.269 [0.817-1.969]; P = .287); overall response rates were 20% and 27%, respectively. Conversely, median overall survival (OS) was 141.9 weeks and 83.3 weeks (hazard ratio 0.734 [0.380-1.419]; P = .356). Overall, 61% and 55% of patients in the perifosine and placebo arms reported grade 3/4 adverse events, including thrombocytopenia (26% vs 14%), anemia (7% vs 8%), hyponatremia (6% vs 8%), and pneumonia (9% vs 3%). These findings demonstrate no PFS benefit from the addition of perifosine to bortezomib-dexamethasone in this study of relapsed/refractory MM, but comparable safety and OS.

The circular RNA NT5E promotes non-small cell lung cancer cell growth via sponging microRNA-134

The current study tested expression and potential function of circular RNA ecto-5’-nucleotidase (circNT5E) in human non-small cell lung cancer (NSCLC). We show that circNT5E levels are significantly elevated in human NSCLC tissues and cells, correlating with downregulation of its potential targets, miR-134, miR-422a and miR-338. In A549 and primary NSCLC cells, circNT5E shRNA inhibited cancer cell growth, proliferation and migration, whiling inducing apoptosis activation. Conversely, ectopic circNT5E overexpression promoted A549 cell progression in vitro. miR-134 is the primary target of circNT5E in lung cancer cells. RNA-Pull down assay in A549 cells confirmed the direct association between biotinylated-miR-134 and circNT6E. miR-134 levels were significantly increased in circNT5E-silenced A549 cells, but reduced with circNT5E overexpression. Forced overexpression of miR-134 mimicked circNT5E shRNA-induced actions, inhibiting NSCLC cell growth and proliferation. In contrast, miR-134 inhibition largely attenuated circNT5E shRNA-induced anti-NSCLC cell activity. Importantly, circNT5E shRNA was ineffective in miR-134-overexpressed A549 cells. Collectively, circNT5E promotes human NSCLC cell progression possibly by sponging miR-134.

The Application of Arsenic Trioxide in Ameliorating ABT-737 Target Therapy on Uterine Cervical Cancer Cells through Unique Pathways in Cell Death

ABT-737, a B cell lymphoma-2 (Bcl-2) family inhibitor, activates apoptosis in cancer cells. Arsenic trioxide is an apoptosis activator that impairs cancer cell survival. The aim of this study was to evaluate the effect of a combination treatment with ABT-737 and arsenic trioxide on uterine cervical cancer cells. MTT (3-(4,5-dimethylthiazol-2-yl)-25-diphenyltetrazolium bromide) assay revealed that ABT-737 and arsenic trioxide induced a synergistic effect on uterine cervical cancer cells. Arsenic trioxide enhanced ABT-737-induced apoptosis and caspase-7 activation and the ABT-737-mediated reduction of anti-apoptotic protein Mcl-1 in Caski cells. Western blot assay revealed that arsenic trioxide promoted the ABT-737-mediated reduction of CDK6 and thymidylate synthetase in Caski cells. Arsenic trioxide promoted ABT-737-inhibited mitochondrial membrane potential and ABT-737-inhibited ANT expression in Caski cells. However, ABT-737-elicited reactive oxygen species were not enhanced by arsenic trioxide. The combined treatment induced an anti-apoptosis autophagy in SiHa cells. This study is the first to demonstrate that a combination treatment with ABT-737 and arsenic trioxide induces a synergistic effect on uterine cervical cancer cells through apoptosis. Our findings provide new insights into uterine cervical cancer treatment.

SF2523 inhibits human chondrosarcoma cell growth in vitro and in vivo

Developing novel therapeutic agents against chondrosarcoma is important. SF2523 is a PI3K-Akt-mTOR and bromodomain-containing protein 4 (BRD4) dual inhibitor. Its activity in human chondrosarcoma cells is tested. Our results show that SF2523 potently inhibited survival, proliferation and migration, and induced apoptosis activation in SW1353 cells and primary human chondrosarcoma cells. The dual inhibitor was yet non-cytotoxic to the primary human osteoblasts and OB-6 osteoblastic cells. SF2523 blocked Akt-mTOR activation and downregulated BRD4-regulated genes (Bcl-2 and c-Myc) in chondrosarcoma cells. It was more efficient in killing chondrosarcoma cells than other established PI3K-Akt-mTOR and BRD4 inhibitors, including JQ1, perifosine and OSI-027. In vivo, intraperitoneal injection of SF2523 (30 mg/kg) potently inhibited subcutaneous SW1353 xenograft tumor growth in severe combined immunodeficient mice. Akt-mTOR inhibition as well as Bcl-2 and c-Myc downregulation were detected in SF2523-treated SW1353 tumor tissues. In conclusion, targeting PI3K-Akt-mTOR and BRD4 by SF2523 potently inhibited chondrosarcoma cell growth in vitro and in vivo.

Circular RNA HIPK3 exerts oncogenic properties through suppression of miR-124 in lung cancer

The current study tested the expression and potential functions of circular RNA HIPK3 (circHIPK3) in human lung cancer. Our results show that circHIPK3 expression is upregulated in established (A549 line) and primary human lung cancer cells, when compared to its low level in the lung epithelial cells. siRNA-mediated silencing of circHIPK3 potently inhibited survival and proliferation of lung cancer cells, but inducing significant apoptosis activation. Contrarily, forced overexpression of circHIPK3 by a lentiviral construct promoted lung cancer cell survival and proliferation. CircHIPK3 acted as a microRNA-124 (miR-124) sponger and regulated the expression of miR-124 mRNA targets, including SphK1, CDK4 and STAT3, in lung cancer cells. Transfection of miR-124 inhibitor significantly inhibited circHIPK3 siRNA-induced lung cancer cell death and apoptosis. At last, we show that circHIPK3 levels are upregulated in human lung cancer tissues, correlated with miR-124 downregulation. The miR-124 targets (SphK1, STAT3 and CDK4) are upregulated in lung cancer tissues. Together, we propose that circHIPK3 promotes lung cancer cell progression possibly by sponging miR-124. These observations indicate a possible novel therapeutic strategy involving circHIPK3-miR-124 pathway against lung cancer.

Long non-coding RNA EPIC1 promotes human lung cancer cell growth

Long non-coding RNA (LncRNA) EPIC1 (Lnc-EPIC1) is a MYC-interacting LncRNA. In the present study, the expression and potential function of Lnc-EPIC1 in human lung cancer cells are tested. We show that Lnc-EPIC1 expression is significantly higher in established/primary human lung cancer cells than that in human lung epithelial cells. Lnc-EPIC1 is also elevated in human lung cancer tissues. Silencing of Lnc-EPIC1 by targeted siRNA significantly inhibited human lung cancer cell growth, survival and proliferation, whiling inducing G1-S cell cycle arrest and cell apoptosis. MYC targets, including Cyclin A1, CDC20 and CDC45, were downregulated by Lnc-EPIC1 siRNA. MYC knockout by CRISPR/Cas-9 gene-editing method mimicked actions by Lnc-EPIC1 siRNA in A549 cells. Conversely, forced overexpression of Lnc-EPIC1 by a lentiviral construct increased expression of MYC targets to promote A549 cell growth. Lnc-EPIC1 directly associated with MYC protein in the nuclei of A549 cells. Significantly MYC knockout abolished Lnc-EPIC1 silencing- or overexpression-induced actions in human lung cancer cells. Together, our results show that Lnc-EPIC1 promotes human lung cancer cell growth possibly by targeting MYC.

Identification of mTOR as a primary resistance factor of the IAP antagonist AT406 in hepatocellular carcinoma cells

Dysregulation of inhibitor of apoptosis (IAP) proteins (IAPs) in hepatocellular carcinoma (HCC) is often associated with poor prognosis. Here we showed that AT406, an IAP antagonist, was cytotoxic and pro-apoptotic to both established (HepG2, SMMC-7721 lines) and primary HCC cells. Activation of mTOR could be a key resistance factor of AT406 in HCC cells. mTOR inhibition (by OSI-027), kinase-dead mutation or knockdown remarkably enhanced AT406-induced lethality in HCC cells. Reversely, forced-activation of mTOR by adding SC79 or exogenous expressing a constitutively active S6K1 (T389E) attenuated AT406-induced cytotoxicity against HCC cells. We showed that AT406 induced degradation of IAPs (cIAP-1 and XIAP), but didn't affect another anti-apoptosis protein Mcl-1. Co-treatment of OSI-027 caused simultaneous Mcl-1 downregulation to overcome AT406's resistance. Significantly, shRNA knockdown of Mcl-1 remarkably facilitated AT406-induced apoptosis in HCC cells. In vivo, AT406 oral administration suppressed HepG2 tumor growth in nude mice. Its activity was potentiated with co-administration of OSI-027. We conclude that mTOR could be a key resistance factor of AT406 in HCC cells.

The sphingosine kinase 2 inhibitor ABC294640 inhibits cervical carcinoma cell growth

ABC294640 is a specific sphingosine kinase 2 (SphK2) inhibitor. The anti-cervical carcinoma activity by ABC294640 was tested in this study. ABC294640 inhibited in vitro growth of the established (C33A and HeLa lines) and primary human cervical carcinoma cells. The SphK2 inhibitor also induced G1-S arrest and apoptosis in cervical carcinoma cells. It was yet non-cytotoxic to SphK2-low human cervical epithelial cells. ABC294640 inhibited SphK activation, causing sphingosine-1-phosphate depletion, signal transducer and activator of transcription 3 in-activation and ceramide production. Bcl-2 is a key resistance factor of ABC294640. Pharmacological Bcl-2 inhibition or Bcl-2 shRNA potentiated ABC294640-induced C33A cell growth inhibition and apoptosis. On the other hand, exogenous over-expression of Bcl-2 attenuated ABC294640's cytotoxicity against C33A cells. In vivo, ABC294640 administration inhibited C33A xenograft tumor growth in mice. Co-administration of the Bcl-2 inhibitor GDC-0199 further potentiated ABC294640's anti-tumor activity. Together, we suggest that ABC294640 might have translational value for the treatment of human cervical carcinoma.

PI3K-Akt Signal Transduction Molecules Maybe Involved in Downregulation of Erythroblasts Apoptosis and Perifosine Increased Its Apoptosis in Chronic Mountain Sickness

Background

Chronic mountain sickness (CMS) has a higher incidence in the plateau region. The one of its principal characters is excessive erythrocytosis. The PI3K-Akt pathway plays an important role in the process of erythropoiesis, and could downregulate apoptosis by regulating apoptosis-related molecules. In this paper, we explored the change in apoptosis of erythroblasts and the effect of the PI3K-Akt signal pathway on erythroblasts apoptosis in CMS.

Material/Methods

A total of 22 CMS and 20 non-CMS participants were involved in this study. Bone marrow mononuclear cells were cultured and treated with celecoxib and perifosine in vitro for 72 hours. The apoptotic rate, the mRNA expressions of Akt, Bcl-xl, and caspase-9, and the protein expressions of Akt, p-Akt, Bcl-xl, and caspase-9 were determined by flow cytometry, quantitative RT-PCR, and western-blot technique.

Results

The apoptotic rate of cultured erythroblasts was lower in the CMS group than in the non-CMS group. It was increased after perifosine intervention. The mRNA and protein expressions of Akt and Bcl-xl were higher and caspase-9 was lower in the CMS group than the non-CMS group. Perifosine induced decreased Bcl-xl mRNA and proteins and p-Akt proteins, and increased caspase-9 mRNA and proteins in vitro. In the CMS group, the hemoglobin concentration was correlated with apoptotic rate negatively and with Bcl-xl mRNA positively in erythroblasts; the erythroblasts apoptotic rate was negatively associated with the Akt mRNA and Bcl-xl mRNA.

Conclusion

The erythroblasts apoptosis was downregulated and the PI3K-Akt signal pathway appeared to be involved in the mechanism of decreased erythroblasts apoptosis in CMS.

Phospho-Akt overexpression is prognostic and can be used to tailor the synergistic interaction of Akt inhibitors with gemcitabine in pancreatic cancer

BACKGROUND

There is increasing evidence of a constitutive activation of Akt in pancreatic ductal adenocarcinoma (PDAC), associated with poor prognosis and chemoresistance. Therefore, we evaluated the expression of phospho-Akt in PDAC tissues and cells, and investigated molecular mechanisms influencing the therapeutic potential of Akt inhibition in combination with gemcitabine.

METHODS

Phospho-Akt expression was evaluated by immunohistochemistry in tissue microarrays (TMAs) with specimens tissue from radically-resected patients (n = 100). Data were analyzed by Fisher and log-rank test. In vitro studies were performed in 14 PDAC cells, including seven primary cultures, characterized for their Akt1 mRNA and phospho-Akt/Akt levels by quantitative-RT-PCR and immunocytochemistry. Growth inhibitory effects of Akt inhibitors and gemcitabine were evaluated by SRB assay, whereas modulation of Akt and phospho-Akt was investigated by Western blotting and ELISA. Cell cycle perturbation, apoptosis-induction, and anti-migratory behaviors were studied by flow cytometry, AnnexinV, membrane potential, and migration assay, while pharmacological interaction with gemcitabine was determined with combination index (CI) method.

RESULTS

Immunohistochemistry of TMAs revealed a correlation between phospho-Akt expression and worse outcome, particularly in patients with the highest phospho-Akt levels, who had significantly shorter overall and progression-free-survival. Similar expression levels were detected in LPC028 primary cells, while LPC006 were characterized by low phospho-Akt. Remarkably, Akt inhibitors reduced cancer cell growth in monolayers and spheroids and synergistically enhanced the antiproliferative activity of gemcitabine in LPC028, while this combination was antagonistic in LPC006 cells. The synergistic effect was paralleled by a reduced expression of ribonucleotide reductase, potentially facilitating gemcitabine cytotoxicity. Inhibition of Akt decreased cell migration and invasion, which was additionally reduced by the combination with gemcitabine. This combination significantly increased apoptosis, associated with induction of caspase-3/6/8/9, PARP and BAD, and inhibition of Bcl-2 and NF-kB in LPC028, but not in LPC006 cells. However, targeting the key glucose transporter Glut1 resulted in similar apoptosis induction in LPC006 cells.

CONCLUSIONS

These data support the analysis of phospho-Akt expression as both a prognostic and a predictive biomarker, for the rational development of new combination therapies targeting the Akt pathway in PDAC. Finally, inhibition of Glut1 might overcome resistance to these therapies and warrants further studies.

Small Molecular TRAIL Inducer ONC201 Induces Death in Lung Cancer Cells: A Preclinical Study

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) selectively targets cancer cells. The present preclinical study investigated the anti-cancer efficiency of ONC201, a first-in-class small molecule TRAIL inducer, in lung cancer cells. We showed that ONC201 was cytotoxic and anti-proliferative in both established (A549 and H460 lines) and primary human lung cancer cells. It was yet non-cytotoxic to normal lung epithelial cells. Further, ONC201 induced exogenous apoptosis activation in lung cancer cells, which was evidenced by TRAIL/death receptor-5 (DR5) induction and caspase-8 activation. The caspase-8 inhibitor or TRAIL/DR5 siRNA knockdown alleviated ONC201's cytotoxicity against lung cancer cells. Molecularly, ONC201 in-activated Akt-S6K1 and Erk signalings in lung cancer cells, causing Foxo3a nuclear translocation. For the in vivo studies, intraperitoneal injection of ONC201 at well-tolerated doses significantly inhibited xenografted A549 tumor growth in severe combined immunodeficient (SCID) mice. Further, ONC201 administration induced TRAIL/DR5 expression, yet inactivated Akt-S6K1 and Erk in tumor tissues. These results of the study demonstrates the potent anti-lung cancer activity by ONC201.

Inhibition of ceramide glucosylation sensitizes lung cancer cells to ABC294640, a first-in-class small molecule SphK2 inhibitor

Sphingosine kinase 2 (SphK2) is proposed as a novel oncotarget for lung cancer. Here, we studied the anti-lung cancer cell activity by ABC294640, a first-in-class SphK2 inhibitor. We showed that ABC294640 suppressed growth of primary and A549 human lung cancer cells, but sparing SphK2-low lung epithelial cells. Inhibition of SphK2 by ABC294640 increased ceramide accumulation, but decreased pro-survival sphingosine-1-phosphate (S1P) content, leading to lung cancer cell apoptosis activation. Significantly, we show that glucosylceramide synthase (GCS) might be a major resistance factor of ABC294640. The GCS inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) or GCS shRNA/siRNA knockdown facilitated ABC294640-induced ceramide production and lung cancer cell apoptosis. Reversely, forced overexpression of GCS reduced ABC294640's sensitivity, resulting in decreased ceramide accumulation and apoptosis induction in A549 cells. These findings provide further evidences to support that targeting SphK2 by ABC294640 may be a rational treatment option for lung cancer. Ceramide glucosylation inhibition may further sensitize lung cancer cells to ABC294640.