Abstract 272: Autophagy and MEK inhibition promotes ferroptosis in liver kinase B1 (Lkb1)-deficient Kras-driven lung tumors

Tumor suppressor Liver Kinase B1 (LKB1) activates 5’-adenosine monophosphate protein kinase (AMPK) and maintains energy homeostasis in response to energy crises. LKB1 and KRAS are the third most frequent co-mutations detected in non-small cell lung cancer (NSCLC), causing aggressive tumor growth and metastases. Unfortunately, standard treatment with RAS-RAF-MEK-ERK signaling pathway inhibitors has minimal therapeutic efficacy in LKB1-mutant KRAS-driven NSCLC. Thus, identifying a novel treatment for patients harboring co-mutations in LKB1 and KRAS is urgently needed. Autophagy degrades and recycles the building blocks for cancer cells to survive metabolic challenges. Using genetically engineered mouse models (GEMMs), we have previously demonstrated that autophagy compensates for Lkb1 loss for Kras-driven lung tumorigenesis; loss of an autophagy-essential gene Atg7 dramatically impaired tumor initiation and tumor growth in KrasG12D/+;Lkb1−/− (KL) lung tumors. This is in sharp contrast to Lkb1 wild-type (WT) (KrasG12D/+;p53−/− (KP)) tumors that are less sensitive to autophagy gene ablation. To further value our discoveries in clinical translational ability, we treated mouse lung tumor derived cell lines (TDCLs) with FDA-approved autophagy inhibitor hydroxychloroquine (HCQ) and MEK inhibitor Trametinib and found that the combination treatment displayed synergistic anti-proliferative effects in KL TDCLs compared to KP TDCLs. To elucidate the underlying mechanism of increased sensitivity of KL TDCLs to Trametinib by autophagy ablation, we performed metabolomic profiling of KL TDCLs with Trametinib, HCQ, or combination treatment and found that several glycolytic and TCA cycle intermediates, amino acids, and ATP levels were significantly upregulated upon treatment with Trametinib, which were significantly reduced by the combination treatment. In addition, the combination treatment significantly reduced mitochondrial membrane potential, basal respiration, and ATP production in KL TDCLs. In vivo studies using tumor allografts, genetically engineered mouse models (GEMMs) and patient-derived xenografts (PDXs) showed anti-tumor activity of the combination treatment on KL tumors, but not in KP tumors. Moreover, we found increased lipid peroxidation indicative of ferroptosis in KL TDCLs and KL PDX tumors with the combination treatment compared to the single agent treatments. Finally, treatment with a ferroptosis inhibitor rescued the reduced KL allograft tumor growth caused by the combination treatment. Taken together, our observations indicate that autophagy upregulation in KL tumors causes resistance to Trametinib treatment by maintaining energy homeostasis for cell survival and inhibits ferroptosis. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1-deficient KRAS-driven NSCLC.

Citation Format: Vrushank Bhatt, Taijin Lan, Wenping Wang, Jerry Kong, Eduardo Cararo Lopes, Khoosheh Khayati, Jianming Wang, Akash Raju, Michael Rangel, Enrique Lopez, Zhixian Sherrie Hu, Xuefei Luo, Xiaoyang Su, Jyoti Malhotra, Wenwei Hu, Sharon R. Pine, Eileen White, Jessie Yanxiang Guo. Autophagy and MEK inhibition promotes ferroptosis in liver kinase B1 (Lkb1)-deficient Kras-driven lung tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 272.

Inhibition of autophagy and MEK promotes ferroptosis in Lkb1-deficient Kras-driven lung tumors

LKB1 and KRAS are the third most frequent co-mutations detected in non-small cell lung cancer (NSCLC) and cause aggressive tumor growth. Unfortunately, treatment with RAS-RAF-MEK-ERK pathway inhibitors has minimal therapeutic efficacy in LKB1-mutant KRAS-driven NSCLC. Autophagy, an intracellular nutrient scavenging pathway, compensates for Lkb1 loss to support Kras-driven lung tumor growth. Here we preclinically evaluate the possibility of autophagy inhibition together with MEK inhibition as a treatment for Kras-driven lung tumors. We found that the combination of the autophagy inhibitor hydroxychloroquine (HCQ) and the MEK inhibitor Trametinib displays synergistic anti-proliferative activity in Kras^G12D/+;Lkb1^-/- (KL) lung cancer cells, but not in Kras^G12D/+;p53^-/- (KP) lung cancer cells. In vivo studies using tumor allografts, genetically engineered mouse models (GEMMs) and patient-derived xenografts (PDXs) showed anti-tumor activity of the combination of HCQ and Trametinib on KL but not KP tumors. We further found that the combination treatment significantly reduced mitochondrial membrane potential, basal respiration, and ATP production, while also increasing lipid peroxidation, indicative of ferroptosis, in KL tumor-derived cell lines (TDCLs) and KL tumors compared to treatment with single agents. Moreover, the reduced tumor growth by the combination treatment was rescued by ferroptosis inhibitor. Taken together, we demonstrate that autophagy upregulation in KL tumors causes resistance to Trametinib by inhibiting ferroptosis. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat NSCLC bearing co-mutations of LKB1 and KRAS.

Abstract 88: Autophagy inhibition sensitizes liver kinase b1 (LKB1)-deficient kras-driven lung tumors to MEK inhibitor trametinib

Tumor suppressor Liver Kinase B1 (LKB1) activates 5'-adenosine monophosphate protein kinase (AMPK) and maintains energy homeostasis in response to energy crises. LKB1 and KRAS are the third most frequent co-mutations detected in non-small cell lung cancer (NSCLC), causing aggressive tumor growth, metastases, and resistance to standard chemotherapy as well as immunotherapy. Thus, identifying a novel treatment for patients harboring co-mutations in LKB1 and KRAS is urgently needed. Autophagy degrades and recycles the building blocks for cancer cells to survival metabolic challenges. Using genetically engineered mouse models (GEMMs), we have previously demonstrated that autophagy compensates for Lkb1 loss for KRAS-driven lung tumorigenesis; loss of an autophagy-essential gene Atg7 dramatically impaired tumor initiation and tumor growth in KrasG12D/+;Lkb1-/- (KL) lung tumors. This is in sharp contrast to Lkb1 wild-type (WT) (KrasG12D/+;p53-/- (KP)) tumors that are less sensitive to autophagy gene ablation. To further value our discoveries in clinical translational ability, we treated mouse lung tumor-derived cell lines (TDCLs) with FDA-approved autophagy inhibitor hydroxychloroquine (HCQ) and found that KL TDCLs were much sensitive to HCQ-induced cell death compared with KP TDCLs. Furthermore, a combination treatment of HCQ with mitogen-activated protein kinase kinase (MAPKK or MEK) inhibitor Trametinib showed synergistic anti-proliferative effects in KL TDCLs, but not in KP TDCLs. To elucidate the underlying mechanism of the increased sensitivity of KL TDCLs to Trametinib by autophagy ablation, we performed metabolomic profiling of KL TDCLs with Trametinib, HCQ, or combination treatment. We found that several glycolytic and TCA cycle intermediates, amino acids, and ATP levels were significantly upregulated upon treatment with Trametinib, which were significantly reduced by the combination treatment. Also, the combination treatment significantly reduced the mitochondrial membrane potential, basal respiration, and ATP production in the KL TDCLs compared with the single agents. However, these effects were not observed in KP TDCLs. Similarly, we found that LKB1-mutant human lung cancer cell lines were much more sensitive to the combination treatment than LKB1 WT cells. Finally, we performed in vivo tumor assay using allograft mouse models and GEMMs to validate our in vitro observations. We found anti-tumor synergistic effects of the combination treatment in KL tumor growth, with no such effect in KP tumor growth. Taken together, our observation suggests that autophagy upregulation in Lkb1-deficient tumors cause resistance to Trametinib treatment by maintaining energy homeostasis for cell survival. Therefore, a combination of autophagy and MEK inhibition could be a novel therapeutic strategy to specifically treat LKB1-deficient NSCLC.

Citation Format: Vrushank Dharmesh Bhatt, Taijin Lan, Wenping Wang, Khoosheh Khayati, Eduardo Cararo-Lopes, Jianming Wang, Jerry Kong, Akash Raju, Xuefei Luo, Wenwei Hu, Xiaoyang Su, Eileen White, Jessie Yanxiang Guo. Autophagy inhibition sensitizes liver kinase b1 (LKB1)-deficient kras-driven lung tumors to MEK inhibitor trametinib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 88.

Physiologic pineal region, choroid plexus, and dural calcifications in the first decade of life

BACKGROUND AND PURPOSE

Calcifications of the pineal, habenula, choroid plexus, and dura are often physiologic. In the modern CT era with thin-section images and multiplanar reformats, intracranial calcifications have become more conspicuous. We aimed to discover the CT prevalence of pineal region, choroid plexus, and dural calcifications in the first decade of life.

MATERIALS AND METHODS

Five hundred head CTs from different patients (age range, 0-9 years) encountered during a consecutive 6-month period at a single academic children's hospital were reviewed retrospectively after excluding examinations with artifacts and pineal region masses/hemorrhage. All studies were performed on a 320-detector CT, with 0.5-mm collimation and a 512 × 512 matrix. Five-millimeter reformatted axial, sagittal, and coronal images were analyzed for location and extent of intracranial calcifications.

RESULTS

The mean age was 3.5 ± 5.7 years (range, 0-9 years). There were 285 males (57%) and 215 females (43%). Pineal calcifications were present in 5% (n = 25; age range, 3.2-8.9 years; median, 7 years). Habenular calcifications were found in 10% (n = 50; age range, 2.8-8.8 years; median, 7 years). Twelve percent (n = 58) had choroid plexus calcifications, (age range, 0.1-8.8 years). Dural calcifications were rare, present in 1% (n = 6; age range, 2.9-8.7 years).

CONCLUSIONS

Physiologic intracranial calcifications may be found in the first decade, principally in children older than 5 years. Most epithalamic calcifications are habenular. Pineal and habenular calcifications were never present in children younger than 3 and 2 years, respectively. Choroid plexus calcifications may be present in the very young. Dural calcifications are rare.

Chronic pain after caesarean delivery: an Australian cohort

We investigated the incidence of and risk factors for persistent pain after caesarean delivery. Over a 12-month period, women having caesarean delivery were recruited prospectively at an Australian tertiary referral centre. Demographic, anaesthetic and surgical data were collected and at 24 hour follow-up, women were assessed for immediate postoperative pain and preoperative expectations of pain. Long-term telephone follow-up was conducted at two and 12 months postoperatively. Complete data were obtained from 426 of 469 women initially recruited (90.6%). The incidence of persistent pain at the abdominal wound at two months was 14.6% (n=62) but subsequently reduced to 4.2% (n=18) at 12 months. At two months, 33 patients (7.8%) experienced constant or daily pain. At 12 months, five patients (1.1%) continued to have constant or daily pain which was mild. There was no apparent increase in incidence of persistent pain associated with general versus regional anaesthesia (relative risk [RR] 0.89, 95% confidence interval [CI] 0.49 to 1.6); emergency vs elective procedure (RR 0.65, 95% CI 0.39 to 1.07); higher acute pain scores (RR 1.1, 95% CI 0.69 to 1.75); or history of previous caesarean delivery (RR 0.81, 95% CI 0.50 to 1.33). Persistent pain, usually of a mild nature, is reported by some women two months after their caesarean delivery, but by 12 months less than 1% of women had pain requiring analgesia or affecting mood or sleep. All declined a pain clinic review. Clinicians and patients can be reassured that caesarean delivery is unlikely to lead to severe persistent pain in the long-term.

Identification, purification, and characterization of a thermally stable lipase from rice bran. A new member of the (phospho) lipase family

A thermally stable lipase (EC 3.1.1.3.) was first identified in rice (Oryza sativa) bran, and the enzyme was purified to homogeneity using octyl-Sepharose chromatography. The enzyme was purified to 7.6-fold with the final specific activity of 0.38 micromol min(-1) mg(-1) at 80 degrees C using [9,10-(3)H]triolein as a substrate. The purified enzyme was found to be a glycoprotein of 9.4 kD. Enzyme showed a maximum activity at 80 degrees C and at pH 11.0. The protein was biologically active and retained most of its secondary structure even at 90 degrees C as judged by the enzymatic assays and far-ultraviolet circular dichroism spectroscopy, respectively. Differential scanning calorimetric studies indicated that the transition temperature was 76 degrees C and enthalpy 1.3 x 10(5) Calorie mol(-1) at this temperature. The purified lipase also exhibited phospholipase A(2) activity. Colocalization of both the hydrolytic activities in reverse-phase high-performance liquid chromatography and isoelectric focusing showed that the dual activity was associated with a single protein. Further, a direct interaction between both the substrates and the purified protein was demonstrated by photoaffinity labeling, using chemically synthesized analogs of triolein and phosphatidylcholine (PC). Apparent K(m) for triolein (6.71 mM) was higher than that for PC (1.02 mM). The enzyme preferentially hydrolyzed the sn-2 position of PC, whereas it apparently exhibited no positional specificity toward triacylglycerol. Diisopropyl fluorophosphate inhibited both lipase and phospholipase activities of the purified enzyme. This enzyme is a new member from plants in the family of lipases capable of hydrolyzing phospholipids.

Occupational noise exposure and hearing levels

A study was made at the Bhabha Atomic Research Center to measure the hearing levels of persons working in a noisy environment. Two different workplaces, central air-conditioning plant and glass flowing shops, where a number of persons were exposed to noise levels exceeding 85 dB(A) were chosen. The occupational exposure to noise was determined using a sound level meter, an octave band filter and a personal noise dose meter. The hearing levels of persons exposed to these high levels of noise and a control group not exposed to occupational noise were measured by means of a pure-tone audiometer in a specially-build booth. These persons, aged between 20 to 60 years, were divided into four age groups for the study. The low ambient noise levels in the booth were measured using correlation technique since such low signals cannot be detected by an ordinary sound level meter. The audiometric findings and the results of the noise level survey are discussed in this paper.