Overexpression of lysophospholipid acyltransferase, LPLAT10/LPCAT4/LPEAT2, in the mouse liver increases glucose-stimulated insulin secretion.

Postprandial hyperglycemia is an early indicator of impaired glucose tolerance that leads to type 2 diabetes mellitus (T2DM). Alterations in the fatty acid composition of phospholipids have been implicated in diseases such as T2DM and nonalcoholic fatty liver disease. Lysophospholipid acyltransferase 10 (LPLAT10, also called LPCAT4 and LPEAT2) plays a role in remodeling fatty acyl chains of phospholipids; however, its relationship with metabolic diseases has not been fully elucidated. LPLAT10 expression is low in the liver, the main organ that regulates metabolism, under normal conditions. Here, we investigated whether overexpression of LPLAT10 in the liver leads to improved glucose metabolism. For overexpression, we generated an LPLAT10-expressing adenovirus (Ad) vector (Ad-LPLAT10) using an improved Ad vector. Postprandial hyperglycemia was suppressed by the induction of glucose-stimulated insulin secretion in Ad-LPLAT10-treated mice compared with that in control Ad vector-treated mice. Hepatic and serum levels of phosphatidylcholine 40:7, containing C18:1 and C22:6, were increased in Ad-LPLAT10-treated mice. Serum from Ad-LPLAT10-treated mice showed increased glucose-stimulated insulin secretion in mouse insulinoma MIN6 cells. These results indicate that changes in hepatic phosphatidylcholine species due to liver-specific LPLAT10 overexpression affect the pancreas and increase glucose-stimulated insulin secretion. Our findings highlight LPLAT10 as a potential novel therapeutic target for T2DM.

Intraneural fibrosis within ilioinguinal nerve in inguinal hernia patients with preoperative pain: it's the sign of irreversible nerve injury, isn't it?

PURPOSE: Preoperative pain is known as one of the most powerful risk factors for chronic postoperative inguinal pain (CPIP), while its pathogenesis has not been fully elucidated. The aim of the present study was to evaluate patients with preoperative pain from the pathological perspective and discuss the potential pathogenesis of CPIP in those patients. METHODS: This was a single-institutional retrospective study. The study population was inguinal hernia patients with preoperative pain who underwent open anterior hernia repair for primary inguinal hernia with pragmatic ilioinguinal neurectomy during surgery between March 2021 and March 2023. The primary and secondary outcomes were proportion of collagen deposition and mucus accumulation within ilioinguinal nerve in those patients, respectively, which were evaluated histologically using Image J software. RESULTS: Forty patients were evaluated. Median value of proportion of intraneural collagen deposition was 38.3% (27.7-95.9). These values were positively correlated with the duration of pain (r2=0.468, P<0.001). Median value of proportion of mucus accumulation in ilioinguinal nerve was 50.1% (0-82.0). These values had no correlation with any clinicopathological variables. CONCLUSIONS: In the present study population, all patients with preoperative pain had intraneural fibrosis within ilioinguinal nerve, and its degree had a positive correlation with the pain duration.

Phosphatidylinositol-3,4,5-trisphosphate interacts with alpha-synuclein and initiates its aggregation and formation of Parkinson's disease-related fibril polymorphism.

Lipid interaction with α-synuclein (αSyn) has been long implicated in the pathogenesis of Parkinson's disease (PD). However, it has not been fully determined which lipids are involved in the initiation of αSyn aggregation in PD. Here exploiting genetic understanding associating the loss-of-function mutation in Synaptojanin 1 (SYNJ1), a phosphoinositide phosphatase, with familial PD and analysis of postmortem PD brains, we identified a novel lipid molecule involved in the toxic conversion of αSyn and its relation to PD. We first established a SYNJ1 knockout cell model and found SYNJ1 depletion increases the accumulation of pathological αSyn. Lipidomic analysis revealed SYNJ1 depletion elevates the level of its substrate phosphatidylinositol-3,4,5-trisphosphate (PIP3). We then employed Caenorhabditis elegans model to examine the effect of SYNJ1 defect on the neurotoxicity of αSyn. Mutations in SYNJ1 accelerated the accumulation of αSyn aggregation and induced locomotory defects in the nematodes. These results indicate that functional loss of SYNJ1 promotes the pathological aggregation of αSyn via the dysregulation of its substrate PIP3, leading to the aggravation of αSyn-mediated neurodegeneration. Treatment of cultured cell line and primary neurons with PIP3 itself or with PIP3 phosphatase inhibitor resulted in intracellular formation of αSyn inclusions. Indeed, in vitro protein-lipid overlay assay validated that phosphoinositides, especially PIP3, strongly interact with αSyn. Furthermore, the aggregation assay revealed that PIP3 not only accelerates the fibrillation of αSyn, but also induces the formation of fibrils sharing conformational and biochemical characteristics similar to the fibrils amplified from the brains of PD patients. Notably, the immunohistochemical and lipidomic analyses on postmortem brain of patients with sporadic PD showed increased PIP3 level and its colocalization with αSyn. Taken together, PIP3 dysregulation promotes the pathological aggregation of αSyn and increases the risk of developing PD, and PIP3 represents a potent target for intervention in PD.

Mid-term outcomes of intracorporeal versus extracorporeal anastomosis after laparoscopic colectomy: a propensity score-matched cohort study from a single institution.

PURPOSE: There is still insufficient discussion of the mid- to long-term safety of the intracorporeal anastomosis (IA) method of reconstruction after laparoscopic colectomy (LAC) for colon cancer. The present study clarified the postoperative mid-term results of IA based on recurrence and the incidence of incision hernia. METHODS: This single-institution observational retrospective study included 268 patients with colon cancer who underwent IA or extracorporeal anastomosis (EA) after LAC at our institution between 2018 and 2021. The mid-term results of the IA group were compared with those of the EA group using a propensity score matching method. RESULTS: The median follow-up periods were 36 and 25 months in the EA and IA groups, respectively (p < 0.0001). In this matched cohort study, the recurrence-free survival (RFS) rates were comparable between the IA and EA groups (each group, n = 72; 3-year RFS: IA, 92.1%; EA, 88.2%; hazard ratio, 0.78; 95% confidence interval, 0.25-2.40; p = 0.66). The cumulative incisional hernia rates were 9.8% and 9.9% (p = 0.99) for the IA and EA groups, respectively. CONCLUSION: The safety of IA after LAC was demonstrated in this study, as IA after LAC showed good mid-term results, including with regard to the rates of recurrence and incisional hernia.

[Usefulness of Nutritional Evaluation in Adjuvant Chemotherapy for Colorectal Cancer in Older Patients].

OBJECTIVE: To clarify the usefulness of Onodera's prognostic nutritional index(OPNI)in adjuvant chemotherapy(AC)for older patients with colorectal cancer. MATERIALS AND METHODS: This study included 39 patients aged over 70 years who underwent AC for colorectal cancer from August 2009 to February 2018. We evaluated the association of OPNI with AC toxicities and prognosis. RESULTS: OPNI was an independent predictor of toxicities of Grade 3 or higher(OR: 0.18, 95%CI: 0.043-0.75, p=0.019). The 3-year recurrence-free survival rate was significantly better in the higher OPNI group than in the lower OPNI group(89.9% and 66.7%, respectively; HR: 0.19, 95%CI: 0.04-0.92, p=0.038). There was a positive correlation with Spearman's rank correlation coefficient of 0.66 in OPNI before and after AC(p<0.001). CONCLUSION: OPNI could be one of the valuable predictors of AC toxicities and the prognosis. There was a high correlation between OPNI before and after AC. These findings suggest the importance of early nutritional support for patients with lower OPNI.

Laparoscopic Colectomy for a Patient with Situs Inversus Totalis: The Usefulness of Preoperative Assessment.

BACKGROUND Situs inversus totalis (SIT) is a rare congenital anomaly in which the patient's internal organs are positioned in a mirror image of their normal locations. Laparoscopic surgery for a patient with SIT requires modification of the standard procedure. Several studies have recently reported surgical techniques for laparoscopic colectomy in patients with SIT. Herein, we present the case of a patient with congenital SIT who underwent laparoscopic colectomy for transverse colon cancer with intracorporeal anastomosis and discuss the usefulness of preoperative assessment. CASE REPORT A 63-year-old woman with SIT was referred to our department for surgical intervention following endoscopic submucosal dissection of transverse colon cancer. We performed a successful laparoscopic colectomy with intracorporeal anastomosis. Our team had no prior experience performing laparoscopic surgery on a patient with SIT; however, preoperative image training using a horizontally flipped video of a normal laparoscopic colectomy enabled the operation to be performed safely. Preoperative image training is very useful for gaining an understanding of images similar to the actual field of view before surgery. The patient was discharged without complications on the eighth postoperative day. CONCLUSIONS Careful preoperative assessment that takes into consideration the mirror-image anatomy and the contemplated laparoscopic procedure should allow patients with SIT to fully benefit from minimally invasive surgery.

Plasma membrane phosphatidylinositol (4,5)-bisphosphate is critical for determination of epithelial characteristics.

Epithelial cells provide cell-cell adhesion that is essential to maintain the integrity of multicellular organisms. Epithelial cell-characterizing proteins, such as epithelial junctional proteins and transcription factors are well defined. However, the role of lipids in epithelial characterization remains poorly understood. Here we show that the phospholipid phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] is enriched in the plasma membrane (PM) of epithelial cells. Epithelial cells lose their characteristics upon depletion of PM PI(4,5)P2, and synthesis of PI(4,5)P2 in the PM results in the development of epithelial-like morphology in osteosarcoma cells. PM localization of PARD3 is impaired by depletion of PM PI(4,5)P2 in epithelial cells, whereas expression of the PM-targeting exocyst-docking region of PARD3 induces osteosarcoma cells to show epithelial-like morphological changes, suggesting that PI(4,5)P2 regulates epithelial characteristics by recruiting PARD3 to the PM. These results indicate that a high level of PM PI(4,5)P2 plays a crucial role in the maintenance of epithelial characteristics.

[Retrospective Analysis of Adjuvant Chemotherapy for Elderly Patients with Stage â ¢ Colorectal Cancer].

OBJECTIVE: To investigate the efficacy and toxicity of adjuvant chemotherapy(AC)in elderly patients with Stage Ⅲ colorectal cancer(CRC). METHODS: We performed a single-institutional retrospective analysis of 84 patients aged≥75 years with Stage Ⅲ CRC who underwent curative resection from August 2009 to February 2018. RESULTS: Thirty-seven(44.0%) patients received AC. Eleven(29.7%)patients required dose reduction at the start of AC. Twenty-three(62.2%)patients accomplished AC, and 13(35.1%)needed dose reduction during AC. Although toxicities of Grade 3 or higher occurred in 56.8% of patients, they were controllable. The 3-year recurrence-free survival rate was significantly better in the AC group than in the non-AC group(70.3% versus 50.5%, respectively; p=0.011). The prognosis tended to be worse in the group that started AC with dose reduction than in the group with the normal dose. CONCLUSION: AC is effective and well tolerated in elderly patients with Stage Ⅲ CRC. When reducing the initial dose, the need for dose reduction should be carefully considered.

A mass spectrometric method for in-depth profiling of phosphoinositide regioisomers and their disease-associated regulation.

Phosphoinositides are a family of membrane lipids essential for many biological and pathological processes. Due to the existence of multiple phosphoinositide regioisomers and their low intracellular concentrations, profiling these lipids and linking a specific acyl variant to a change in biological state have been difficult. To enable the comprehensive analysis of phosphoinositide phosphorylation status and acyl chain identity, we develop PRMC-MS (Phosphoinositide Regioisomer Measurement by Chiral column chromatography and Mass Spectrometry). Using this method, we reveal a severe skewing in acyl chains in phosphoinositides in Pten-deficient prostate cancer tissues, extracellular mobilization of phosphoinositides upon expression of oncogenic PIK3CA, and a unique profile for exosomal phosphoinositides. Thus, our approach allows characterizing the dynamics of phosphoinositide acyl variants in intracellular and extracellular milieus.

Short-term outcomes of intracorporeal versus extracorporeal anastomosis after laparoscopic colectomy: a propensity score-matched cohort study from a single institution.

PURPOSE: To compare the postoperative short-term results of intracorporeal anastomosis (IA) using overlap anastomosis (OLA), with those of extracorporeal anastomosis (EA) using functional end-to-end anastomosis (FEEA) or hand-sewn anastomosis (HSA), after laparoscopic colectomy (LAC). METHODS: The subjects of this retrospective study were 208 patients with colon cancer who underwent OLA, FEEA, or HSA after LAC at our institution, between 2018 and 2021. The short-term results of the OLA group were compared with those of the FEEA and HSA groups, respectively, using a propensity score-matching method. RESULTS: The mean operative time for anastomosis was longer in the OLA group than in the FEEA and HSA groups (p < 0.0001). The mean blood loss volume was less in the OLA group than in the FEEA and HSA groups (p = 0.0344 and p = 0.0002, respectively). The mean skin incision size was smaller in the OLA group than in the FEEA and HSA groups (p < 0.0001 and p = 0.0031, respectively). None of the patients in the OLA group had surgical site infections. Three to five patients were required for the surgeon to plateau on the learning curve. CONCLUSION: Although IA required more time than EA, the skills appeared to improve with experience and the short-term results were superior to those of EA.

Usefulness of Carcinoembryonic Antigen Doubling Time in Prognosis Prediction after Curative Resection of Locally Recurrent Rectal Cancer: A Retrospective Study.

INTRODUCTION: Given that doubling time is an indicator of tumor growth, we assessed the usefulness of carcinoembryonic antigen doubling time (CEA-DT) in prognosis prediction after curative resection for locally recurrent rectal cancer. METHODS: During January 1986-December 2016, 33 patients with locally recurrent rectal cancer who underwent curative resection at our hospital were retrospectively reviewed. The primary endpoint was the 3-year recurrence-free survival (RFS) rate. The Kaplan-Meier method was used to compare RFS rates and evaluate univariate and multivariate analyses for factors associated with oncologic outcomes, including CEA-DT. CEA-DT was classified into 2 groups: the short and long CEA-DT groups. RESULTS: The 3-year overall survival and RFS rates were 62.6% and 42.4%, respectively. In multivariate analyses, CEA-DT was an independent risk factor for poor RFS. The 3-year RFS rate was significantly better in the long CEA-DT group than in the short CEA-DT group (58.8% vs. 25.0%, p = 0.0063). CONCLUSION: CEA-DT is a useful prognostic factor that can be assessed before surgery for locally recurrent rectal cancer. Long CEA-DT may indicate a favorable prognosis. Contrarily, short CEA-DT is associated with poor prognosis; therefore, further treatment intervention is necessary for patients with short CEA-DT.

PI4P/PS countertransport by ORP10 at ER-endosome membrane contact sites regulates endosome fission.

Membrane contact sites (MCSs) serve as a zone for nonvesicular lipid transport by oxysterol-binding protein (OSBP)-related proteins (ORPs). ORPs mediate lipid countertransport, in which two distinct lipids are transported counterdirectionally. How such lipid countertransport controls specific biological functions, however, remains elusive. We report that lipid countertransport by ORP10 at ER-endosome MCSs regulates retrograde membrane trafficking. ORP10, together with ORP9 and VAP, formed ER-endosome MCSs in a phosphatidylinositol 4-phosphate (PI4P)-dependent manner. ORP10 exhibited a lipid exchange activity toward its ligands, PI4P and phosphatidylserine (PS), between liposomes in vitro, and between the ER and endosomes in situ. Cell biological analysis demonstrated that ORP10 supplies a pool of PS from the ER, in exchange for PI4P, to endosomes where the PS-binding protein EHD1 is recruited to facilitate endosome fission. Our study highlights a novel lipid exchange at ER-endosome MCSs as a nonenzymatic PI4P-to-PS conversion mechanism that organizes membrane remodeling during retrograde membrane trafficking.

Altering phosphoinositides in high-fat diet-associated prostate tumor xenograft growth.

The metabolic reprogramming of phospholipids may affect intracellular signal transduction pathways. A high-fat diet (HFD) is attributed to prostate cancer (PCa) progression, but the expression pattern and role of phospholipids in HFD-mediated PCa progression remains unclear. In this study, HFD enhanced LNCaP xenograft tumor growth by upregulating the phosphatidylinositol (PI) 3-kinase (PI3K)/AKT signaling pathway. A lipidomic analysis using xenograft tumors showed that phosphoinositides, especially PI (3,4,5)-trisphosphate (PIP3), including several species containing C38:4, C38:3, and C40:4 fatty acids, increased in the HFD group compared to control. Fatty acid synthase (FASN) was significantly upregulated in xenograft tumors under HFD in both gene and protein levels. PCa cell growth was significantly inhibited through the decreased AKT signaling pathway by treatment with cerulenin, a chemical FASN inhibitor, which also downregulated PIP, PIP2, and PIP3 but not PI. Thus, dietary fat influences PCa progression and alters phosphoinositides, especially PIP3, a critical player in the PI3K/AKT pathway. These results may offer appropriate targets, such as FASN, for dietary intervention and/or chemoprevention to reduce PCa incidence and progression.

Oncologic outcomes after resection of para-aortic lymph node metastasis in left-sided colon and rectal cancer.

AIM: The optimal surgical management strategy for para-aortic lymph node (PALN) metastasis has not attracted as much attention as surgery for liver or lung metastasis. The purpose of this retrospective study was to evaluate the oncologic outcomes after synchronous resection of PALN metastasis in left-sided colon and rectal cancer. METHODS: Between January 1986 and August 2016, 29 patients with pathologically positive PALN metastases who underwent curative resection at our hospital were retrospectively reviewed. We examined clinicopathological characteristics, long-term oncologic outcomes, and factors related to favorable prognosis in these patients. RESULTS: The 3-year overall survival and recurrence-free survival (RFS) rates were 50.5% and 17.2%, respectively. In total, 6 (20.7%) patients experienced no recurrence in the 3 years after surgery, while postoperative complications were seen in 9 (31.0%) patients. The 3-year RFS rate was significantly better in the pM1a group than in the pM1b/pM1c group (26.3% and 0.0%, respectively, p = 0.032). CONCLUSION: PALN dissection for patients without other organ metastases in left-sided colon or rectal cancer is a good indication as it is for liver and lung metastasis.

Fatty Acid Synthesis Is Indispensable for Survival of Human Pluripotent Stem Cells.

The role of lipid metabolism in human pluripotent stem cells (hPSCs) is poorly understood. We have used large-scale targeted proteomics to demonstrate that undifferentiated hPSCs express different fatty acid (FA) biosynthesis-related enzymes, including ATP citrate lyase and FA synthase (FASN), than those expressed in hPSC-derived cardiomyocytes (hPSC-CMs). Detailed lipid profiling revealed that inhibition of FASN resulted in significant reduction of sphingolipids and phosphatidylcholine (PC); moreover, we found that PC was the key metabolite for cell survival in hPSCs. Inhibition of FASN induced cell death in undifferentiated hPSCs via mitochondria-mediated apoptosis; however, it did not affect cell survival in hPSC-CMs, neurons, or hepatocytes as there was no significant reduction of PC. Furthermore, we did not observe tumor formation following transplantation of FASN inhibitor-treated cells. Our findings demonstrate the importance of de novo FA synthesis in the survival of undifferentiated hPSCs and suggest applications for FASN inhibition in regenerative medicine.

Clinical impact of non-predominant histopathological subtypes on the long-term prognosis of colorectal cancer patients in Japan.

PURPOSE: We performed a retrospective study to clarify the long-term prognosis of patients with histopathological high-grade colorectal cancer (CRC). METHODS: We reviewed data from 24 institutions for 18,360 patients with pStage I to III CRC who had undergone curative surgery between 2004 and 2012. The patients were classified into seven groups according to the proportion of the histopathological component: classical adenocarcinoma (CAC) group, M-l and M-h groups (< 50% and ≥ 50% mucinous adenocarcinoma, respectively), P-l and P-h groups (< 50% and ≥ 50% poorly differentiated adenocarcinoma, respectively), and S-l and S-h groups (< 50% and ≥ 50% signet-ring cell carcinoma (SRCC), respectively). RESULTS: The 5-year recurrence-free survival (RFS) rates of the M-l, P-l, and S-l groups were 75.5%, 68.4%, and 52.4%, respectively, and were significantly lower than those of the CAC group (83.5%, hazard ratio [HR] 1.22, 95% confidence interval [CI] 1.01-1.48, p = 0.0365; HR 1.60, 95% CI 1.32-1.91, p < 0.0001; HR 2.61, 95% CI 1.30-4.57, p = 0.0090, respectively). The 5-year RFS of the P-l and S-l groups was as poor as that of the P-h and S-h groups, respectively (HR 0.87, 95% CI 0.68-1.10, p = 0.25; HR 0.90, 95% CI 0.37-2.13, p = 0.81, respectively). The histopathological component of the S-l group was an independent factor affecting overall survival in multivariate analysis. CONCLUSION: The long-term prognoses of the non-predominant poorly differentiated adenocarcinoma (PAC) groups were as poor as those of the predominant group. In particular, the histopathological component of the P-l and S-l groups could be classified into predominant PAC and SRCC subtypes for appropriate prognostic predictions.

Prognostic impact of the number of lateral pelvic lymph node metastases on rectal cancer.

BACKGROUND: This study aimed to clarify the number of lateral pelvic lymph node metastases of colorectal cancer for which prognosis could be improved by dissection. METHODS: We analysed the data of 30 patients with lateral pelvic lymph node metastases of rectal cancer that underwent a total mesorectal excision with lateral pelvic lymph node dissection at our institute from 1986 to 2016. We performed survival analysis on the number of lateral pelvic lymph node metastases in each of these patients and identified an optimal cut-off point of the number of lateral pelvic lymph node metastases that would predict recurrence-free survival using the receiver operating characteristic curves and an Akaike information criterion value. RESULTS: The 5-year recurrence-free survival and overall survival of patients with one or two lateral pelvic lymph node metastases were significantly better than that of those with three or more (5-year recurrence-free survival, 63.3 vs. 0.0%, respectively; hazard ratio, 0.23; 95% CI, 0.07-0.72; P = 0.0124) (5-year overall survival, 68.2 vs. 15.6%, respectively; hazard ratio, 0.29; 95% CI, 0.09-0.92; P = 0.0300). All of the metastatic lateral pelvic lymph nodes in the group with one or two lateral pelvic lymph node metastases were restricted to the internal iliac artery or obturator nerve regions. CONCLUSIONS: The cut-off number of lateral pelvic lymph node metastases in the internal iliac artery or obturator nerve regions of colorectal cancer cases in whom prognosis was improved by lateral pelvic lymph node dissection was 2; patients who had <3 lateral pelvic lymph node metastases had better prognoses than those with ≥3 lateral pelvic lymph node metastases.

Increased fatty acyl saturation of phosphatidylinositol phosphates in prostate cancer progression.

Phosphoinositides (PIPs) participate in many cellular processes, including cancer progression; however, the metabolic features of PIPs associated with prostate cancer (PCa) are unknown. We investigated PIPs profiles in PTEN-deficient prostate cancer cell lines, human prostate tissues obtained from patients with PCa and benign prostate hyperplasia (BPH) specimens using mass spectrometry. In immortalized normal human prostate PNT1B cells, PTEN deficiency increased phosphatidylinositol tris-phosphate (PIP3) and decreased phosphatidylinositol mono- and bis-phosphate (PIP1 and PIP2), consistent with PTEN's functional role as a PI(3,4,5)P3 3-phosphatase. In human prostate tissues, levels of total (sum of all acyl variants) phosphatidylinositol (PI) and PIP1 in PCa were significantly higher than in BPH, whereas PIP2 and PIP3 contents were significantly lower than in BPH. PCa patients had significantly higher proportion of PI, PIP1, and PIP2 with 0-2 double bonds in acyl chains than BPH patients. In subgroup analyses based on PCa aggressiveness, mean total levels of PI with 0-2 double bonds in acyl chains were significantly higher in patients with pathological stage T3 than in those with pathological stage T2. These data indicate that alteration of PIPs level and the saturation of acyl chains may be associated with the development and aggressiveness of prostate cancer, although it is unknown whether this alteration is causative.

Loss of DDHD2, whose mutation causes spastic paraplegia, promotes reactive oxygen species generation and apoptosis.

DDHD2/KIAA0725p is a mammalian intracellular phospholipase A1 that exhibits phospholipase and lipase activities. Mutation of the DDHD2 gene causes hereditary spastic paraplegia (SPG54), an inherited neurological disorder characterized by lower limb spasticity and weakness. Although previous studies demonstrated lipid droplet accumulation in the brains of SPG54 patients and DDHD2 knockout mice, the cause of SPG54 remains elusive. Here, we show that ablation of DDHD2 in mice induces age-dependent apoptosis of motor neurons in the spinal cord. In vitro, motor neurons and embryonic fibroblasts from DDHD2 knockout mice fail to survive and are susceptible to apoptotic stimuli. Chemical and probe-based analysis revealed a substantial decrease in cardiolipin content and an increase in reactive oxygen species generation in DDHD2 knockout cells. Reactive oxygen species production in DDHD2 knockout cells was reversed by the expression of wild-type DDHD2, but not by an active-site DDHD2 mutant, DDHD2 mutants related to hereditary spastic paraplegia, or DDHD1, another member of the intracellular phospholipase A1 family whose mutation also causes spastic paraplegia (SPG28). Our results demonstrate the protective role of DDHD2 for mitochondrial integrity and provide a clue to the pathogenic mechanism of SPG54.

Metabolic Determinants of Sensitivity to Phosphatidylinositol 3-Kinase Pathway Inhibitor in Small-Cell Lung Carcinoma.

Comprehensive genomic analysis has revealed that the PI3K/AKT/mTOR pathway is a feasible therapeutic target in small-cell lung carcinoma (SCLC). However, biomarkers to identify patients likely to benefit from inhibitors of this pathway have not been identified. Here, we show that metabolic features determine sensitivity to the PI3K/mTOR dual inhibitor gedatolisib in SCLC cells. Substantial phosphatidyl lipid analysis revealed that a specific phosphatidylinositol (3,4,5)-trisphosphate (PIP3) subspecies lipid product PIP3 (38:4) is predictive in assessing sensitivity to PI3K/mTOR dual inhibitor. Notably, we found that higher amounts of purine-related aqueous metabolites such as hypoxanthine, which are characteristic of SCLC biology, lead to resistance to PI3K pathway inhibition. In addition, the levels of the mRNA encoding hypoxanthine phosphoribosyl transferase 1, a key component of the purine salvage pathway, differed significantly between SCLC cells sensitive or resistant to gedatolisib. Moreover, complementation with purine metabolites could reverse the vulnerability to targeting of the PI3K pathway in SCLC cells normally sensitive to gedatolisib. These results indicate that the resistance mechanism of PI3K pathway inhibitors is mediated by the activation of the purine salvage pathway, supplying purine resource to nucleotide biosynthesis. Metabolomics is a powerful approach for finding novel therapeutic biomarkers in SCLC treatment.Significance: These findings identify features that determine sensitivity of SCLC to PI3K pathway inhibition and support metabolomics as a tool for finding novel therapeutic biomarkers. Cancer Res; 78(9); 2179-90. ©2018 AACR.