Targeting LKB1 in cancer - exposing and exploiting vulnerabilities

Metabolic stress induces a double-positive feedback loop between AMPK and SQSTM1/p62 conferring dual activation of AMPK and NFE2L2/NRF2 to synergize antioxidant defense

Co-occurring mutations in KEAP1 in STK11/LKB1-mutant NSCLC activate NFE2L2/NRF2 to compensate for the loss of STK11-AMPK activity during metabolic adaptation. Characterizing the regulatory crosstalk between the STK11-AMPK and KEAP1-NFE2L2 pathways during metabolic stress is crucial for understanding the implications of co-occurring mutations. Here, we found that metabolic stress increased the expression and phosphorylation of SQSTM1/p62, which is essential for the activation of NFE2L2 and AMPK, synergizing antioxidant defense and tumor growth. The SQSTM1-driven dual activation of NFE2L2 and AMPK was achieved by inducing macroautophagic/autophagic degradation of KEAP1 and facilitating the AXIN-STK11-AMPK complex formation on the lysosomal membrane, respectively. In contrast, the STK11-AMPK activity was also required for metabolic stress-induced expression and phosphorylation of SQSTM1, suggesting a double-positive feedback loop between AMPK and SQSTM1. Mechanistically, SQSTM1 expression was increased by the PPP2/PP2A-dependent dephosphorylation of TFEB and TFE3, which was induced by the lysosomal deacidification caused by low glucose metabolism and AMPK-dependent proton reduction. Furthermore, SQSTM1 phosphorylation was increased by MAP3K7/TAK1, which was activated by ROS and pH-dependent secretion of lysosomal Ca2+. Importantly, phosphorylation of SQSTM1 at S24 and S226 was critical for the activation of AMPK and NFE2L2. Notably, the effects caused by metabolic stress were abrogated by the protons provided by lactic acid. Collectively, our data reveal a novel double-positive feedback loop between AMPK and SQSTM1 leading to the dual activation of AMPK and NFE2L2, potentially explaining why co-occurring mutations in STK11 and KEAP1 happen and providing promising therapeutic strategies for lung cancer.Abbreviations: AMPK: AMP-activated protein kinase; BAF1: bafilomycin A1; ConA: concanamycin A; DOX: doxycycline; IP: immunoprecipitation; KEAP1: kelch like ECH associated protein 1; LN: low nutrient; MAP3K7/TAK1: mitogen-activated protein kinase kinase kinase 7; MCOLN1/TRPML1: mucolipin TRP cation channel 1; MEFs: mouse embryonic fibroblasts; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; NFE2L2/NRF2: NFE2 like bZIP transcription factor 2; NSCLC: non-small cell lung cancer; PRKAA/AMPKα: protein kinase AMP-activated catalytic subunit alpha; PPP2/PP2A: protein phosphatase 2; ROS: reactive oxygen species; PPP3/calcineurin: protein phosphatase 3; RPS6KB1/p70S6K: ribosomal protein S6 kinase B1; SQSTM1/p62: sequestosome 1; STK11/LKB1: serine/threonine kinase 11; TCL: total cell lysate; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3; V-ATPase: vacuolar-type H+-translocating ATPase.

Highly Stereoselective Diels-Alder-Based Strategy for the Synthesis of 3-epi-Formicin A and 1-epi-Formicin B

The first enantioselective approach based on a highly stereoselective Diels-Alder reaction for the synthesis of 3-epi-formicin A and 1-epi-formicin B with rare N-acetylcysteamine-containing indenone thioesters is reported. The strategy utilizes a key Diels-Alder reaction to form the core hydrindane system with three contiguous stereocenters in very high levels of diastereo- and regioselectivity and one-pot oxidation/isomerization/dehydrogenation. The scope of this method was tested with different substrates to give cycloadducts in a highly diastereoselective manner.

LKB1 depletion-mediated epithelial-mesenchymal transition induces fibroblast activation in lung fibrosis

The factors that determine fibrosis progression or normal tissue repair are largely unknown. We previously demonstrated that autophagy inhibition-mediated epithelial-mesenchymal transition (EMT) in human alveolar epithelial type II (ATII) cells augments local myofibroblast differentiation in pulmonary fibrosis by paracrine signalling. Here, we report that liver kinase B1 (LKB1) inactivation in ATII cells inhibits autophagy and induces EMT as a consequence. In IPF lungs, this is caused by downregulation of CAB39L, a key subunit within the LKB1 complex. 3D co-cultures of ATII cells and MRC5 lung fibroblasts coupled with RNA sequencing (RNA-seq) confirmed that paracrine signalling between LKB1-depleted ATII cells and fibroblasts augmented myofibroblast differentiation. Together these data suggest that reduced autophagy caused by LKB1 inhibition can induce EMT in ATII cells and contribute to fibrosis via aberrant epithelial-fibroblast crosstalk.

Differences of Pine Wood Nematode (Bursaphelenchus xylophilus) Developmental Stages under High-Osmotic-Pressure Stress

Under ion imbalance, water deficiency, and salt stress, the osmotic pressure of the tree sap increases, and pine wood nematodes (Bursaphelenchus xylophilus, PWN) parasitizing in the trees may be subjected to high-osmotic-pressure stress. KCl, L-malic acid, sucrose, and glycerol solutions were used as osmolytes to explore the highest osmotic concentration that PWN can tolerate. Survival analysis showed that when the treatment concentration exceeded 90%, only a few nematodes in the glycerol group survived under 6 h treatment, and most of the survivors were third-stage dispersal juveniles (DJ3). Further examination revealed that under different concentrations of glycerol-induced high osmotic pressure, the survival rate and body length change rate were the highest in the DJ3 and the lowest in the second-stage propagative juveniles. In order to explore the molecular mechanism of resistance of DJ3 to high osmotic stress, transcriptome sequencing was performed at each developmental stage of PWN and differentially expressed genes that were up-regulated or down-regulated only in DJ3 were screened. The expression of genes related to CoA in DJ3, a key enzyme in metabolism, was significantly higher than the other developmental stages. In addition, the expression of the anti-reversal signal pathway-related gene AKT-1 in DJ3 was significantly lower than in the other development stages. Therefore, the specific expression of genes in DJ3 under high osmotic pressure may help them rapidly produce and accumulate energy-related compounds and activate the adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway to respond to damage caused by high-osmotic-pressure stress in time, thus promoting survival.

Influence of TP53 Comutation on the Tumor Immune Microenvironment and Clinical Outcomes With Immune Checkpoint Inhibitors in STK11-Mutant Non-Small-Cell Lung Cancer

PURPOSE

Non-small-cell lung cancer (NSCLC) with STK11mut has inferior outcomes to immune checkpoint inhibitors (ICIs). Using multiomics, we evaluated whether a subtype of STK11mut NSCLC with a uniquely inflamed tumor immune microenvironment (TIME) harboring TP53 comutations could have favorable outcomes to ICIs.

PATIENTS AND METHODS

NSCLC tumors (N = 16,896) were analyzed by next-generation sequencing (DNA-Seq/592 genes). A subset (n = 5,034) underwent gene expression profiling (RNA-Seq/whole transcriptome). Exome-level neoantigen load for STK11mut NSCLC was obtained from published pan-immune analysis. Tumor immune cell content was obtained from transcriptome profiles using the microenvironment cell population (MCP) counter. ICI data from POPLAR/OAK (n = 34) and the study by Rizvi et al (n = 49) were used to model progression-free survival (PFS), and a separate ICI-treated cohort (n = 53) from Dana-Farber Cancer Institute (DFCI) was used to assess time to treatment failure (TTF) and tumor RECIST response for STK11mutTP53mut versus STK11mutTP53wt NSCLC.

RESULTS

Overall, 12.6% of NSCLC tumors had a STK11mut with the proportions of tumor mutational burden (TMB)-high (≥10 mut/Mb), PD-L1 ≥50%, and microsatellite instability-high being 38.3%, 11.8%, and 0.72%, respectively. Unsupervised hierarchical clustering of STK11mut (n = 463) for stimulator of interferon-gamma (STING) pathway genes identified a STING-high cluster, which was significantly enriched in TP53mut NSCLC (P < .01). Compared with STK11mutTP53wt, tumors with STK11mutTP53mut had higher CD8+T cells and natural killer cells (P < .01), higher TMB (P < .001) and neoantigen load (P < .001), and increased expression of MYC and HIF-1A (P < .01), along with higher expression (P < .01) of glycolysis/glutamine metabolism genes. Meta-analysis of data from OAK/POPLAR and the study by Rizvi et al showed a trend toward improved PFS in patients with STK11mutTP53mut. In the DFCI cohort, compared with the STK11mut TP53wt cohort, the STK11mutTP53mut tumors had higher objective response rates (42.9% v 16.7%; P = .04) and also had longer TTF (14.5 v 4.5 months, P adj = .054) with ICI.

CONCLUSION

STK11mut NSCLC with TP53 comutation is a distinct subgroup with an immunologically active TIME and metabolic reprogramming. These properties should be exploited to guide patient selection for novel ICI-based combination approaches.

Development of a Genetically Engineered Mouse Model Recapitulating LKB1 and PTEN Deficiency in Gastric Cancer Pathogenesis

The LKB1 and PTEN genes are critical in gastric cancer (G.C.) development. LKB1, a robust tumor suppressor gene, encodes a serine/threonine kinase that directly triggers the activation of AMPK-an integral cellular metabolic kinase. The role of the LKB1 pathway extends to maintaining the stability of epithelial junctions by regulating E-cadherin expression. Conversely, PTEN, a frequently mutated tumor suppressor gene in various human cancers, emerges as a pivotal negative regulator of the phosphoinositide 3-kinase (PI3K) signaling pathway. This study is set to leverage the H+/K+ ATPase Cre transgene strain to precisely target Cre recombinase expression at parietal cells within the stomach. This strategic maneuver seeks to selectively nullify the functions of both LKB1 and PTEN in a manner specific to the stomach, thereby instigating the development of G.C. in a fashion akin to human gastric adenocarcinoma. Moreover, this study endeavors to dissect the intricate ways in which these alterations contribute to the histopathologic advancement of gastric tumors, their potential for invasiveness and metastasis, their angiogenesis, and the evolving tumor stromal microenvironment. Our results show that conditional deletion of PTEN and LKB1 provides an ideal cancer microenvironment for G.C. tumorigenesis by promoting cancer cell proliferation, angiogenesis, and metastasis.

Integrative Analysis of a Large Real-World Cohort of Small Cell Lung Cancer Identifies Distinct Genetic Subtypes and Insights into Histologic Transformation

Small cell lung cancer (SCLC) is a recalcitrant neuroendocrine carcinoma with dismal survival outcomes. A major barrier in the field has been the relative paucity of human tumors studied. Here we provide an integrated analysis of 3,600 "real-world" SCLC cases. This large cohort allowed us to identify new recurrent alterations and genetic subtypes, including STK11-mutant tumors (1.7%) and TP53/RB1 wild-type tumors (5.5%), as well as rare cases that were human papillomavirus-positive. In our cohort, gene amplifications on 4q12 are associated with increased overall survival, whereas CCNE1 amplification is associated with decreased overall survival. We also identify more frequent alterations in the PTEN pathway in brain metastases. Finally, profiling cases of SCLC containing oncogenic drivers typically associated with NSCLC demonstrates that SCLC transformation may occur across multiple distinct molecular cohorts of NSCLC. These novel and unsuspected genetic features of SCLC may help personalize treatment approaches for this fatal form of cancer.

SIGNIFICANCE

Minimal changes in therapy and survival outcomes have occurred in SCLC for the past four decades. The identification of new genetic subtypes and novel recurrent mutations as well as an improved understanding of the mechanisms of transformation to SCLC from NSCLC may guide the development of personalized therapies for subsets of patients with SCLC. This article is highlighted in the In This Issue feature, p. 1501.

A phase II study of metformin plus pemetrexed and carboplatin in patients with non-squamous non-small cell lung cancer (METALUNG)

Immune checkpoint inhibitors (ICIs) ± chemotherapy is the standard treatment for driver mutation-negative non-small cell lung cancer (NSCLC). However, accessibility to ICIs in LMICs is limited due to high cost, and platinum-based chemotherapy remains the mainstay of treatment. Metformin has anticancer properties, and studies suggest synergism between metformin and pemetrexed. Based on preclinical evidence, this combination may be more beneficial for STK11-mutated NSCLC, a subgroup, inherently resistant to ICIs. In this Simon two-stage, single-arm phase 2 trial, we investigated metformin with pemetrexed-carboplatin (PC) in patients with treatment-naive stage IV non-squamous NSCLC. The primary outcome was 6-month progression-free survival (PFS) rate. Secondary outcomes were safety, overall survival (OS), overall response rate (ORR), proportion of STK11 mutation, and effect of STK11 mutation on 6-month PFS rate. The study was terminated for futility after interim analysis. The median follow-up was 34.1 months. The 6-month PFS rate was 28% (95% CI 12.4-0.46). The median PFS and OS were 4.5 (95% CI 2.2-6.1) and 7.4 months (95% CI 5.3-15.3), respectively. The ORR was 72%. Gastrointestinal toxicities were the most common. No grade 4/5 toxicities were reported. Targeted sequencing was possible in nine cases. Two patients had STK11 mutation and a poor outcome (PFS < 12 weeks). We could not demonstrate the benefit of metformin with CP in terms of improvement in 6-month PFS rate; however, the combination was safe (CTRI/2019/02/017815).

Prognostic and Predictive Biomarkers in the Era of Immunotherapy for Lung Cancer

The therapeutic algorithm of lung cancer has recently been revolutionized by the emergence of immune checkpoint inhibitors. However, an objective and durable response rate remains low with those recent therapies and some patients even experience severe adverse events. Prognostic and predictive biomarkers are therefore needed in order to select patients who will respond. Nowadays, the only validated biomarker is the PD-L1 expression, but its predictive value remains imperfect, and it does not offer any certainty of a sustained response to treatment. With recent progresses in molecular biology, genome sequencing techniques, and the understanding of the immune microenvironment of the tumor and its host, new molecular features have been highlighted. There are evidence in favor of the positive predictive value of the tumor mutational burden, as an example. From the expression of molecular interactions within tumor cells to biomarkers circulating in peripheral blood, many markers have been identified as associated with the response to immunotherapy. In this review, we would like to summarize the latest knowledge about predictive and prognostic biomarkers of immune checkpoint inhibitors efficacy in order to go further in the field of precision immuno-oncology.

Metabolic reprogramming in cancer: Mechanisms and therapeutics

Cancer cells characterized by uncontrolled growth and proliferation require altered metabolic processes to maintain this characteristic. Metabolic reprogramming is a process mediated by various factors, including oncogenes, tumor suppressor genes, changes in growth factors, and tumor–host cell interactions, which help to meet the needs of cancer cell anabolism and promote tumor development. Metabolic reprogramming in tumor cells is dynamically variable, depending on the tumor type and microenvironment, and reprogramming involves multiple metabolic pathways. These metabolic pathways have complex mechanisms and involve the coordination of various signaling molecules, proteins, and enzymes, which increases the resistance of tumor cells to traditional antitumor therapies. With the development of cancer therapies, metabolic reprogramming has been recognized as a new therapeutic target for metabolic changes in tumor cells. Therefore, understanding how multiple metabolic pathways in cancer cells change can provide a reference for the development of new therapies for tumor treatment. Here, we systemically reviewed the metabolic changes and their alteration factors, together with the current tumor regulation treatments and other possible treatments that are still under investigation. Continuous efforts are needed to further explore the mechanism of cancer metabolism reprogramming and corresponding metabolic treatments.

STK11 Inactivation Predicts Rapid Recurrence in Inoperable Early-Stage Non-Small-Cell Lung Cancer

PURPOSE

Molecular factors predicting relapse in early-stage non-small-cell lung cancer (ES-NSCLC) are poorly understood, especially in inoperable patients receiving radiotherapy (RT). In this study, we compared the genomic profiles of inoperable and operable ES-NSCLC.

MATERIALS AND METHODS

This retrospective study included 53 patients with nonsquamous ES-NSCLC (stage I-II) treated at a single institution (University of Chicago) with surgery (ie, operable; n = 30) or RT (ie, inoperable; n = 23) who underwent tumor genomic profiling. A second cohort of ES-NSCLC treated with RT (Stanford, n = 39) was included to power clinical analyses. Prognostic gene alterations were identified and correlated with clinical variables. The primary clinical end point was the correlation of prognostic genes with the cumulative incidence of relapse, disease-free survival, and overall survival (OS) in a pooled RT cohort from the two institutions (N = 62).

RESULTS

Although the surgery cohort exhibited lower rates of relapse, the RT cohort was highly enriched for somatic STK11 mutations (43% v 6.7%). Receiving supplemental oxygen (odds ratio [OR] = 5.5), 20+ pack-years of tobacco smoking (OR = 6.1), and Black race (OR = 4.3) were associated with increased frequency of STK11 mutations. In the pooled RT cohort (N = 62), STK11 mutation was strongly associated with inferior oncologic outcomes: 2-year incidence of relapse was 62% versus 20% and 2-year OS was 52% versus 85%, remaining independently prognostic on multivariable analyses (relapse: subdistribution hazard ratio = 4.0, P = .0041; disease-free survival: hazard ratio, 6.8, P = .0002; OS: hazard ratio, 6.0, P = .022). STK11 mutations were predominantly associated with distant failure, rather than local.

CONCLUSION

In this cohort of ES-NSCLC, STK11 inactivation was associated with poor oncologic outcomes after RT and demonstrated a novel association with clinical hypoxia, which may underlie its correlation with medical inoperability. Further validation in larger cohorts and investigation of effective adjuvant systemic therapies may be warranted.

Liver Kinase B1 Regulates Remodeling of the Tumor Microenvironment in Triple-Negative Breast Cancer

Liver kinase B1 (LKB1) is a potent tumor suppressor that regulates cellular energy balance and metabolism as an upstream kinase of the AMP-activated protein kinase (AMPK) pathway. LKB1 regulates cancer cell invasion and metastasis in multiple cancer types, including breast cancer. In this study, we evaluated LKB1’s role as a regulator of the tumor microenvironment (TME). This was achieved by seeding the MDA-MB-231-LKB1 overexpressing cell line onto adipose and tumor scaffolds, followed by the evaluation of tumor matrix-induced tumorigenesis and metastasis. Results demonstrated that the presence of tumor matrix enhanced tumorigenesis in both MDA-MB-231 and MDA-MB-231-LKB1 cell lines. Metastasis was increased in both MDA-MB-231 and -LKB1 cells seeded on the tumor scaffold. Endpoint analysis of tumor and adipose scaffolds revealed LKB1-mediated tumor microenvironment remodeling as evident through altered matrix protein production. The proteomic analysis determined that LKB1 overexpression preferentially decreased all major and minor fibril collagens (collagens I, III, V, and XI). In addition, proteins observed to be absent in tumor scaffolds in the LKB1 overexpressing cell line included those associated with the adipose matrix (COL6A2) and regulators of adipogenesis (IL17RB and IGFBP4), suggesting a role for LKB1 in tumor-mediated adipogenesis. Histological analysis of MDA-MB-231-LKB1-seeded tumors demonstrated decreased total fibril collagen and indicated decreased stromal cell presence. In accordance with this, in vitro condition medium studies demonstrated that the MDA-MB-231-LKB1 secretome inhibited adipogenesis of adipose-derived stem cells. Taken together, these data demonstrate a role for LKB1 in regulating the tumor microenvironment through fibril matrix remodeling and suppression of adipogenesis.

Metabolic Reprogramming in Cancer Cells: Emerging Molecular Mechanisms and Novel Therapeutic Approaches

The constant changes in cancer cell bioenergetics are widely known as metabolic reprogramming. Reprogramming is a process mediated by multiple factors, including oncogenes, growth factors, hypoxia-induced factors, and the loss of suppressor gene function, which support malignant transformation and tumor development in addition to cell heterogeneity. Consequently, this hallmark promotes resistance to conventional anti-tumor therapies by adapting to the drastic changes in the nutrient microenvironment that these therapies entail. Therefore, it represents a revolutionary landscape during cancer progression that could be useful for developing new and improved therapeutic strategies targeting alterations in cancer cell metabolism, such as the deregulated mTOR and PI3K pathways. Understanding the complex interactions of the underlying mechanisms of metabolic reprogramming during cancer initiation and progression is an active study field. Recently, novel approaches are being used to effectively battle and eliminate malignant cells. These include biguanides, mTOR inhibitors, glutaminase inhibition, and ion channels as drug targets. This review aims to provide a general overview of metabolic reprogramming, summarise recent progress in this field, and emphasize its use as an effective therapeutic target against cancer.

LKB1: Can We Target an Hidden Target? Focus on NSCLC

LKB1 (liver kinase B1) is a master regulator of several processes such as metabolism, proliferation, cell polarity and immunity. About one third of non-small cell lung cancers (NSCLCs) present LKB1 alterations, which almost invariably lead to protein loss, resulting in the absence of a potential druggable target. In addition, LKB1-null tumors are very aggressive and resistant to chemotherapy, targeted therapies and immune checkpoint inhibitors (ICIs). In this review, we report and comment strategies that exploit peculiar co-vulnerabilities to effectively treat this subgroup of NSCLCs. LKB1 loss leads to an enhanced metabolic avidity, and treatments inducing metabolic stress were successful in inhibiting tumor growth in several preclinical models. Biguanides, by compromising mitochondria and reducing systemic glucose availability, and the glutaminase inhibitor telaglenastat (CB-839), inhibiting glutamate production and reducing carbon intermediates essential for TCA cycle progression, have provided the most interesting results and entered different clinical trials enrolling also LKB1-null NSCLC patients. Nutrient deprivation has been investigated as an alternative therapeutic intervention, giving rise to interesting results exploitable to design specific dietetic regimens able to counteract cancer progression. Other strategies aimed at targeting LKB1-null NSCLCs exploit its pivotal role in modulating cell proliferation and cell invasion. Several inhibitors of LKB1 downstream proteins, such as mTOR, MEK, ERK and SRK/FAK, resulted specifically active on LKB1-mutated preclinical models and, being molecules already in clinical experimentation, could be soon proposed as a specific therapy for these patients. In particular, the rational use in combination of these inhibitors represents a very promising strategy to prevent the activation of collateral pathways and possibly avoid the potential emergence of resistance to these drugs. LKB1-null phenotype has been correlated to ICIs resistance but several studies have already proposed the mechanisms involved and potential interventions. Interestingly, emerging data highlighted that LKB1 alterations represent positive determinants to the new KRAS specific inhibitors response in KRAS co-mutated NSCLCs. In conclusion, the absence of the target did not block the development of treatments able to hit LKB1-mutated NSCLCs acting on several fronts. This will give patients a concrete chance to finally benefit from an effective therapy.

Role of STK11 in ALK‑positive non‑small cell lung cancer (Review)

Anaplastic lymphoma kinase (ALK) inhibitors have been shown to be effective in treating patients with ALK-positive non-small cell lung cancer (NSCLC), and crizotinib, ceritinib and alectinib have been approved as clinical first-line therapeutic agents. The availability of these inhibitors has also largely changed the treatment strategy for advanced ALK-positive NSCLC. However, patients still inevitably develop resistance to ALK inhibitors, leading to tumor recurrence or metastasis. The most critical issues that need to be addressed in the current treatment of ALK-positive NSCLC include the high cost of targeted inhibitors and the potential for increased toxicity and resistance to combination therapy. Recently, it has been suggested that the serine/threonine kinase 11 (STK11) mutation may serve as one of the biomarkers for immunotherapy in NSCLC. Therefore, the main purpose of this review was to summarize the role of STK11 in ALK-positive NSCLC. The present review also summarizes the treatment and drug resistance studies in ALK-positive NSCLC and the current status of STK11 research in NSCLC.

STK11 Prevents Invasion through Signal Transducer and Activator of Transcription 3/5 and FAK Repression in Cutaneous Melanoma

The STK11/LKB1 is a tumor suppressor involved in metabolism and cell motility. In BRAFV600E melanoma, STK11 is inactivated by extracellular signal‒regulated kinase and RSK, preventing it from binding and activating adenosine monophosphate-activated protein kinase and promoting melanoma cell proliferation. Although STK11 mutations occur in 5‒10% of cutaneous melanoma, few functional studies have been performed. By knocking out STK11 with CRISPR/Cas9 in two human BRAF-mutant melanoma cell lines, we found that STK11 loss reduced the sensitivity to a BRAF inhibitor. More strikingly, STK11 loss led to an increased invasive phenotype in both three-dimensional spheroids and in vivo zebrafish xenograft models. STK11 overexpression consistently reversed the invasive phenotype. Interestingly, STK11 knockout increased invasion also in an NRAS-mutant melanoma cell line. Furthermore, although STK11 was expressed in primary human melanoma tumors, its expression significantly decreased in melanoma metastases, especially in brain metastases. In the STK11-knockout cells, we observed increased activating phosphorylation of signal transducer and activator of transcription 3/5 and FAK. Using inhibitors of signal transducer and activator of transcription 3/5 and FAK, we reversed the invasive phenotype in both BRAF- and NRAS-mutated cells. Our findings confirm an increased invasive phenotype on STK11 inactivation in BRAF- and NRAS-mutant cutaneous melanoma that can be targeted by signal transducer and activator of transcription 3/5 and FAK inhibition.

Blood-Derived Extracellular Vesicle-Associated miR-3182 Detects Non-Small Cell Lung Cancer Patients

Simple Summary

Lung cancer is the leading cause of cancer-related death worldwide as patients are burdened with incredibly poor prognosis. Low survival rates are primarily attributed to lack of early detection and, therefore, timely therapeutic interventions. Late diagnosis is essentially caused by absent and non-specific symptoms, and compounded by inadequate diagnostic tools. We show here that a lung cancer biomarker, based on a simple blood test, might provide promising advantages for diagnostic assessment. Small extracellular vesicles (sEVs) are miniscule messengers that carry cancer biomarkers and are easily detected in the blood. We identify that the abundance of a specific micro-RNA, miR-3182, in these sEVs can be detected in the blood of lung cancer patients but not in controls with benign lung conditions. This demonstrates the potential use of miR-3182 as a biomarker for lung cancer diagnosis.

Abstract

With five-year survival rates as low as 3%, lung cancer is the most common cause of cancer-related mortality worldwide. The severity of the disease at presentation is accredited to the lack of early detection capacities, resulting in the reliance on low-throughput diagnostic measures, such as tissue biopsy and imaging. Interest in the development and use of liquid biopsies has risen, due to non-invasive sample collection, and the depth of information it can provide on a disease. Small extracellular vesicles (sEVs) as viable liquid biopsies are of particular interest due to their potential as cancer biomarkers. To validate the use of sEVs as cancer biomarkers, we characterised cancer sEVs using miRNA sequencing analysis. We found that miRNA-3182 was highly enriched in sEVs derived from the blood of patients with invasive breast carcinoma and NSCLC. The enrichment of sEV miR-3182 was confirmed in oncogenic, transformed lung cells in comparison to isogenic, untransformed lung cells. Most importantly, miR-3182 can successfully distinguish early-stage NSCLC patients from those with benign lung conditions. Therefore, miR-3182 provides potential to be used for the detection of NSCLC in blood samples, which could result in earlier therapy and thus improved outcomes and survival for patients.

Are we still on the right path(way)?: the altered expression of the pentose phosphate pathway in solid tumors and the potential of its inhibition in combination therapy

INTRODUCTION

The pentose phosphate pathway (PPP) branches from glycolysis and is crucial for cell growth, since it provides necessary compounds for anabolic reactions, nucleotide synthesis, and detoxification of reactive-oxygen-species (ROS). Overexpression of PPP enzymes has been reported in multiple cancer types and linked to therapy resistance, making their inhibition interesting targets for anti-cancer therapies.

AREAS COVERED

This review summarizes the extent of PPP upregulation across different cancer types, and the non-metabolic functions that PPP-enzymes might contribute to cancer initiation and maintenance. The effects of PPP-inhibition and their combinations with chemotherapeutics are summarized. We searched the databases provided by the University of Amsterdam to characterize the altered expression of the PPP across different cancer types, and to identify the effects of PPP-inhibition.

EXPERT OPINION

It can be concluded that there are synergistic and additive effects of PPP-inhibition and various classes of chemotherapeutics. These effects may be attributed to the increased susceptibility to ROS. However, the toxicity, low efficacy, and off-target effects of PPP-inhibitors make application in clinical practice challenging. Novel inhibitors are currently being developed, which could make PPP-inhibition a potential therapeutic strategy in the future, especially in combination with conventional chemotherapeutics and the inhibition of other metabolic pathways.

Unraveling the Role of STK11/LKB1 in Non-small Cell Lung Cancer

There are two major groups of lung cancer: non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). NSCLCs can be further separated into three different categories: lung adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Pulmonary adenocarcinomas represent nearly half of all lung cancer cases and are known to be caused by smoking, certain occupational exposures, and specific genetic mutations. Scientists have noticed that most NSCLCs are driven by defects in the following genes: EGFR, BRAF, ALK, MET, and HER. Abnormalities in the STK11/LKB1 gene have also been shown to induce lung adenocarcinoma. LKB1-deficient cancer cells contain an overactive AMPK “energy sensor,” which inhibits cellular death and promotes glucose, lipid, and protein synthesis via the mTOR protein complex. Studies have also discovered that the loss of STK11/LKB1 favors oncogenesis by creating an immunosuppressive environment for tumors to grow and accelerate events such as angiogenesis, epithelial-mesenchymal transition (EMT), and cell polarity destabilization. STK11/LKB1-mutant lung cancers are currently treated with radiotherapy with or without chemotherapy. Recent clinical trials studying the effects of glutaminase inhibitors, mTOR inhibitors, and anti-PD-L1 therapy in lung cancer patients have yielded promising results. This narrative review provides an overview of the STK11/LKB1 gene and its role in cancer development. Additionally, a summary of the LKB1/APMK/mTOR is provided.

STK11/LKB1 Modulation of the Immune Response in Lung Cancer: From Biology to Therapeutic Impact

The STK11/LKB1 gene codes for liver kinase B1 (STK11/LKB1), a highly conserved serine/threonine kinase involved in many energy-related cellular processes. The canonical tumor-suppressive role for STK11/LKB1 involves the activation of AMPK-related kinases, a master regulator of cell survival during stress conditions. In pre-clinical models, inactivation of STK11/LKB1 leads to the progression of lung cancer with the acquisition of metastatic properties. Moreover, preclinical and clinical data have shown that inactivation of STK11/LKB1 is associated with an inert tumor immune microenvironment, with a reduced density of infiltrating cytotoxic CD8⁺ T lymphocytes, a lower expression of PD-(L)1, and a neutrophil-enriched tumor microenvironment. In this review, we first describe the biological function of STK11/LKB1 and the role of its inactivation in cancer cells. We report descriptive epidemiology, co-occurring genomic alterations, and prognostic impact for lung cancer patients. Finally, we discuss recent data based on pre-clinical models and lung cancer cohorts analyzing the results of STK11/LKB1 alterations on the immune system and response or resistance to immune checkpoint inhibitors.

Clinical and Preclinical Outcomes of Combining Targeted Therapy With Radiotherapy

In the era of precision medicine, radiation medicine is currently focused on the precise delivery of highly conformal radiation treatments. However, the tremendous developments in targeted therapy are yet to fulfill their full promise and arguably have the potential to dramatically enhance the radiation therapeutic ratio. The increased ability to molecularly profile tumors both at diagnosis and at relapse and the co-incident progress in the field of radiogenomics could potentially pave the way for a more personalized approach to radiation treatment in contrast to the current ‘‘one size fits all’’ paradigm. Few clinical trials to date have shown an improved clinical outcome when combining targeted agents with radiation therapy, however, most have failed to show benefit, which is arguably due to limited preclinical data. Several key molecular pathways could theoretically enhance therapeutic effect of radiation when rationally targeted either by directly enhancing tumor cell kill or indirectly through the abscopal effect of radiation when combined with novel immunotherapies. The timing of combining molecular targeted therapy with radiation is also important to determine and could greatly affect the outcome depending on which pathway is being inhibited.

EVT-701 is a novel selective and safe mitochondrial complex 1 inhibitor with potent anti-tumor activity in models of solid cancers

Targeting the first protein complex of the mitochondrial electron transport chain (MC1) in cancer has become an attractive therapeutic approach in the recent years, given the metabolic vulnerabilities of cancer cells. The anticancer effect exerted by the pleiotropic drug metformin and the associated reduction in hypoxia-inducible factor 1α (HIF-1α) levels putatively mediated by MC1 inhibition led to the development of HIF-1α inhibitors, such as BAY87-2243, with a more specific MC1 targeting. However, the development of BAY87-2243 was stopped early in phase 1 due to dose-independent emesis and thus there is still no clinical proof of concept for the approach. Given the importance of mitochondrial metabolism during cancer progression, there is still a strong therapeutic need to develop specific and safe MC1 inhibitors. We recently reported the synthesis of compounds with a novel chemotype and potent action on HIF-1α degradation and MC1 inhibition. We describe here the selectivity, safety profile and anti-cancer activity in solid tumors of lead compound EVT-701. In addition, using murine models of lung cancer and of Non-Hodgkin's B cell lymphoma we demonstrated that EVT-701 reduced tumor growth and lymph node invasion when used as a single agent therapy. LKB1 deficiency in lung cancer was identified as a potential indicator of accrued sensitivity to EVT-701, allowing stratification and selection of patients in clinical trials. Altogether these results support further evaluation of EVT-701 alone or in combination in preclinical models and eventually in patients.

Gene of the month: STK11

STK11 encodes for the protein liver kinase B1, a serine/threonine kinase which is involved in a number of physiological processes including regulation of cellular metabolism, cell polarity and the DNA damage response. It acts as a tumour suppressor via multiple mechanisms, most classically through AMP-activated protein kinase-mediated inhibition of the mammalian target of rapamycin signalling pathway. Germline loss-of-function mutations in STK11 give rise to Peutz-Jeghers syndrome, which is associated with hamartomatous polyps of the gastrointestinal tract, mucocutaneous pigmentation and a substantially increased lifetime risk of many cancers. In the sporadic setting, STK11 mutations are commonly seen in a subset of adenocarcinomas of the lung in addition to a number of other tumours occurring at various sites. Mutations in STK11 have been associated with worse prognoses across a range of malignancies and may be a predictor of poor response to immunotherapy in a subset of lung cancers, though further studies are needed before the presence of STK11 mutations can be implemented as a routine clinical biomarker.

New Insight into the Effects of Metformin on Diabetic Retinopathy, Aging and Cancer: Nonapoptotic Cell Death, Immunosuppression, and Effects beyond the AMPK Pathway

Under metabolic stress conditions such as hypoxia and glucose deprivation, an increase in the AMP:ATP ratio activates the AMP-activated protein kinase (AMPK) pathway, resulting in the modulation of cellular metabolism. Metformin, which is widely prescribed for type 2 diabetes mellitus (T2DM) patients, regulates blood sugar by inhibiting hepatic gluconeogenesis and promoting insulin sensitivity to facilitate glucose uptake by cells. At the molecular level, the most well-known mechanism of metformin-mediated cytoprotection is AMPK pathway activation, which modulates metabolism and protects cells from degradation or pathogenic changes, such as those related to aging and diabetic retinopathy (DR). Recently, it has been revealed that metformin acts via AMPK- and non-AMPK-mediated pathways to exert effects beyond those related to diabetes treatment that might prevent aging and ameliorate DR. This review focuses on new insights into the anticancer effects of metformin and its potential modulation of several novel types of nonapoptotic cell death, including ferroptosis, pyroptosis, and necroptosis. In addition, the antimetastatic and immunosuppressive effects of metformin and its hypothesized mechanism are also discussed, highlighting promising cancer prevention strategies for the future.

ONC212 is a Novel Mitocan Acting Synergistically with Glycolysis Inhibition in Pancreatic Cancer

ONC212 is a fluorinated imipridone with preclinical efficacy against pancreatic and other malignancies. Although mitochondrial protease ClpP was identified as an ONC212-binding target, the mechanism leading to cancer cell death is incompletely understood. We investigated mitochondrial dysfunction and metabolic rewiring triggered by ONC212 in pancreatic cancer, a deadly malignancy with an urgent need for novel therapeutics. We found ClpP is expressed in pancreatic cancer cells and is required for ONC212 cytotoxicity. ClpX, the regulatory binding partner of ClpP, is suppressed upon ONC212 treatment. Immunoblotting and extracellular flux analysis showed ONC212 impairs oxidative phosphorylation (OXPHOS) with decrease in mitochondrial-derived ATP production. Although collapse of mitochondrial function is observed across ONC212-treated cell lines, only OXPHOS-dependent cells undergo apoptosis. Cells relying on glycolysis undergo growth arrest and upregulate glucose catabolism to prevent ERK1/2 inhibition and apoptosis. Glucose restriction or combination with glycolytic inhibitor 2-deoxy-D-glucose synergize with ONC212 and promote apoptosis in vitro and in vivo Thus, ONC212 is a novel mitocan targeting oxidative metabolism in pancreatic cancer, leading to different cellular outcomes based on divergent metabolic programs.

Orchestration of tissue-scale mechanics and fate decisions by polarity signalling

Eukaryotic development relies on dynamic cell shape changes and segregation of fate determinants to achieve coordinated compartmentalization at larger scale. Studies in invertebrates have identified polarity programmes essential for morphogenesis; however, less is known about their contribution to adult tissue maintenance. While polarity-dependent fate decisions in mammals utilize molecular machineries similar to invertebrates, the hierarchies and effectors can differ widely. Recent studies in epithelial systems disclosed an intriguing interplay of polarity proteins, adhesion molecules and mechanochemical pathways in tissue organization. Based on major advances in biophysics, genome editing, high-resolution imaging and mathematical modelling, the cell polarity field has evolved to a remarkably multidisciplinary ground. Here, we review emerging concepts how polarity and cell fate are coupled, with emphasis on tissue-scale mechanisms, mechanobiology and mammalian models. Recent findings on the role of polarity signalling for tissue mechanics, micro-environmental functions and fate choices in health and disease will be summarized.

Massively parallel sequencing analysis of 68 gastric-type cervical adenocarcinomas reveals mutations in cell cycle-related genes and potentially targetable mutations

Gastric-type cervical adenocarcinoma (GCA) is an aggressive type of endocervical adenocarcinoma characterized by mucinous morphology, gastric-type mucin, lack of association with human papillomavirus (HPV) and resistance to chemo/radiotherapy. We characterized the landscape of genetic alterations in a large cohort of GCAs, and compared it with that of usual-type HPV-associated endocervical adenocarcinomas (UEAs), pancreatic adenocarcinomas (PAs) and intestinal-type gastric adenocarcinomas (IGAs). GCAs (n = 68) were subjected to massively parallel sequencing targeting 410-468 cancer-related genes. Somatic mutations and copy number alterations (CNAs) were determined using validated bioinformatics methods. Mutational data for UEAs (n = 21), PAs (n = 178), and IGAs (n = 148) from The Cancer Genome Atlas (TCGA) were obtained from cBioPortal. GCAs most frequently harbored somatic mutations in TP53 (41%), CDKN2A (18%), KRAS (18%), and STK11 (10%). Potentially targetable mutations were identified in ERBB3 (10%), ERBB2 (8%), and BRAF (4%). GCAs displayed low levels of CNAs with no recurrent amplifications or homozygous deletions. In contrast to UEAs, GCAs harbored more frequent mutations affecting cell cycle-related genes including TP53 (41% vs 5%, p < 0.01) and CDKN2A (18% vs 0%, p = 0.01), and fewer PIK3CA mutations (7% vs 33%, p = 0.01). TP53 mutations were less prevalent in GCAs compared to PAs (41% vs 56%, p < 0.05) and IGAs (41% vs 57%, p < 0.05). GCAs showed a higher frequency of STK11 mutations than PAs (10% vs 2%, p < 0.05) and IGAs (10% vs 1%, p < 0.05). GCAs harbored more frequent mutations in ERBB2 and ERBB3 (9% vs 1%, and 10% vs 0.5%, both p < 0.01) compared to PAs, and in CDKN2A (18% vs 1%, p < 0.05) and KRAS (18% vs 6%, p < 0.05) compared to IGAs. GCAs harbor recurrent somatic mutations in cell cycle-related genes and in potentially targetable genes, including ERBB2/3. Mutations in genes such as STK11 may be used as supportive evidence to help distinguish GCAs from other adenocarcinomas with similar morphology in metastatic sites.

Oxidative stress-mediated AMPK inactivation determines the high susceptibility of LKB1-mutant NSCLC cells to glucose starvation

The liver kinase B1 (LKB1) is an important tumor suppressor and its loss-of-function mutations are observed in around 16% of non-small cell lung cancer (NSCLC) cases. One of the main functions of LKB1 is to activate AMP-activated protein kinase (AMPK) via direct phosphorylation. Under metabolic or energy stress conditions, the LKB1-AMPK axis inhibits the anabolic pathways and activates the catabolic pathways to maintain metabolic homeostasis for cell survival. In this study, we found that LKB1-mutant NSCLC cells are particularly susceptible to cell death induced by glucose starvation, but not by other forms of starvation such as amino acid starvation or serum starvation. Reconstitution of LKB1 in LKB1-mutant cells or LKB1 knockout in LKB1-wild type cells highlighted the importance of the LKB1-AMPK axis for cell survival under glucose starvation. Mechanistically, in LKB1-mutant cells, glucose starvation elicits oxidative stress, which causes AMPK protein oxidation and inactivation, and eventually cell death. Importantly, this process could be effectively reversed and rescued by 2DG (a glucose analog capable of producing NADPH, a key antioxidant), A769662 (an allosteric AMPK activator), and N-acetyl cysteine (NAC) (a ROS scavenger), indicating the presence of a vicious circle between AMPK inactivation and ROS in LKB1-mutant NSCLC cells under glucose starvation. Our study thus elucidates the critical role of redox balance in determining the susceptibility to cell death under glucose starvation in LKB1-mutant NSCLC cells. The findings from this study reveal important clues in search of novel therapeutic strategies for LKB1-mutant NSCLC by targeting glucose metabolism and redox balance.

Genetic manipulation of LKB1 elicits lethal metastatic prostate cancer

Gene dosage is a key defining factor to understand cancer pathogenesis and progression, which requires the development of experimental models that aid better deconstruction of the disease. Here, we model an aggressive form of prostate cancer and show the unconventional association of LKB1 dosage to prostate tumorigenesis. Whereas loss of Lkb1 alone in the murine prostate epithelium was inconsequential for tumorigenesis, its combination with an oncogenic insult, illustrated by Pten heterozygosity, elicited lethal metastatic prostate cancer. Despite the low frequency of LKB1 deletion in patients, this event was significantly enriched in lung metastasis. Modeling the role of LKB1 in cellular systems revealed that the residual activity retained in a reported kinase-dead form, LKB1^K78I, was sufficient to hamper tumor aggressiveness and metastatic dissemination. Our data suggest that prostate cells can function normally with low activity of LKB1, whereas its complete absence influences prostate cancer pathogenesis and dissemination.

The cutting-edge progress of immune-checkpoint blockade in lung cancer

Great advances in immune checkpoint blockade have resulted in a paradigm shift in patients with lung cancer. Immune-checkpoint inhibitor (ICI) treatment, either as monotherapy or combination therapy, has been established as the standard of care for patients with locally advanced/metastatic non-small cell lung cancer without EGFR/ALK alterations or extensive-stage small cell lung cancer. An increasing number of clinical trials are also ongoing to further investigate the role of ICIs in patients with early-stage lung cancer as neoadjuvant or adjuvant therapy. Although PD-L1 expression and tumor mutational burden have been widely studied for patient selection, both of these biomarkers are imperfect. Due to the complex cancer-immune interactions among tumor cells, the tumor microenvironment and host immunity, collaborative efforts are needed to establish a multidimensional immunogram to integrate complementary predictive biomarkers for personalized immunotherapy. Furthermore, as a result of the wide use of ICIs, managing acquired resistance to ICI treatment remains an inevitable challenge. A deeper understanding of the underlying biological mechanisms of acquired resistance to ICIs is helpful to overcome these obstacles. In this review, we describe the cutting-edge progress made in patients with lung cancer, the optimal duration of ICI treatment, ICIs in some special populations, the unique response patterns during ICI treatment, the emerging predictive biomarkers, and our understanding of primary and acquired resistance mechanisms to ICI treatment.

The level of oncogenic Ras determines the malignant transformation of Lkb1 mutant tissue in vivo

The genetic and metabolic heterogeneity of RAS-driven cancers has confounded therapeutic strategies in the clinic. To address this, rapid and genetically tractable animal models are needed that recapitulate the heterogeneity of RAS-driven cancers in vivo. Here, we generate a Drosophila melanogaster model of Ras/Lkb1 mutant carcinoma. We show that low-level expression of oncogenic Ras (RasLow) promotes the survival of Lkb1 mutant tissue, but results in autonomous cell cycle arrest and non-autonomous overgrowth of wild-type tissue. In contrast, high-level expression of oncogenic Ras (RasHigh) transforms Lkb1 mutant tissue resulting in lethal malignant tumors. Using simultaneous multiview light-sheet microcopy, we have characterized invasion phenotypes of Ras/Lkb1 tumors in living larvae. Our molecular analysis reveals sustained activation of the AMPK pathway in malignant Ras/Lkb1 tumors, and demonstrate the genetic and pharmacologic dependence of these tumors on CaMK-activated Ampk. We further show that LKB1 mutant human lung adenocarcinoma patients with high levels of oncogenic KRAS exhibit worse overall survival and increased AMPK activation. Our results suggest that high levels of oncogenic KRAS is a driving event in the malignant transformation of LKB1 mutant tissue, and uncovers a vulnerability that may be used to target this aggressive genetic subset of RAS-driven tumors.

The Importance of STK11/LKB1 Assessment in Non-Small Cell Lung Carcinomas

Despite the recent implementation of immunotherapy as a single treatment or in combination with chemotherapy for first-line treatment of advanced non-small cell lung cancer (NSCLC), many patients do not benefit from this regimen due to primary treatment resistance or toxicity. Consequently, there is an urgent need to develop efficient biomarkers that can select patients who will benefit from immunotherapy thereby providing the appropriate treatment and avoiding toxicity. One of the biomarkers recently described for the stratification of NSCLC patients undergoing immunotherapy are mutations in STK11/LKB1, which are often associated with a lack of response to immunotherapy in some patients. Therefore, the purpose of this review is to describe the different cellular mechanisms associated with STK11/LKB1 mutations, which may explain the lack of response to immunotherapy. Moreover the review addresses the co-occurrence of additional mutations that may influence the response to immunotherapy and the current clinical studies that have further explored STK11/LKB1 as a predictive biomarker. Additionally this work includes the opportunities and limitations to look for the STK11/LKB1 status in the therapeutic strategy for NSCLC patients.

A Critical Review of the Evidence That Metformin Is a Putative Anti-Aging Drug That Enhances Healthspan and Extends Lifespan

The numerous beneficial health outcomes associated with the use of metformin to treat patients with type 2 diabetes (T2DM), together with data from pre-clinical studies in animals including the nematode, C. elegans, and mice have prompted investigations into whether metformin has therapeutic utility as an anti-aging drug that may also extend lifespan. Indeed, clinical trials, including the MILES (Metformin In Longevity Study) and TAME (Targeting Aging with Metformin), have been designed to assess the potential benefits of metformin as an anti-aging drug. Preliminary analysis of results from MILES indicate that metformin may induce anti-aging transcriptional changes; however it remains controversial as to whether metformin is protective in those subjects free of disease. Furthermore, despite clinical use for over 60 years as an anti-diabetic drug, the cellular mechanisms by which metformin exerts either its actions remain unclear. In this review, we have critically evaluated the literature that has investigated the effects of metformin on aging, healthspan and lifespan in humans as well as other species. In preparing this review, particular attention has been placed on the strength and reproducibility of data and quality of the study protocols with respect to the pharmacokinetic and pharmacodynamic properties of metformin. We conclude that despite data in support of anti-aging benefits, the evidence that metformin increases lifespan remains controversial. However, via its ability to reduce early mortality associated with various diseases, including diabetes, cardiovascular disease, cognitive decline and cancer, metformin can improve healthspan thereby extending the period of life spent in good health. Based on the available evidence we conclude that the beneficial effects of metformin on aging and healthspan are primarily indirect via its effects on cellular metabolism and result from its anti-hyperglycemic action, enhancing insulin sensitivity, reduction of oxidative stress and protective effects on the endothelium and vascular function.

Targeting cancer-cell mitochondria and metabolism to improve radiotherapy response

Radiotherapy is a regimen that uses ionising radiation (IR) to treat cancer. Despite the availability of several therapeutic options, cancer remains difficult to treat and only a minor percentage of patients receiving radiotherapy show a complete response to the treatment due to development of resistance to IR (radioresistance). Therefore, radioresistance is a major clinical problem and is defined as an adaptive response of the tumour to radiation-induced damage by altering several cellular processes which sustain tumour growth including DNA damage repair, cell cycle arrest, alterations of oncogenes and tumour suppressor genes, autophagy, tumour metabolism and altered reactive oxygen species. Cellular organelles, in particular mitochondria, are key players in mediating the radiation response in tumour, as they regulate many of the cellular processes involved in radioresistance. In this article has been reviewed the recent findings describing the cellular and molecular mechanism by which cancer rewires the function of the mitochondria and cellular metabolism to enhance radioresistance, and the role that drugs targeting cellular bioenergetics have in enhancing radiation response in cancer patients.

Beyond Tumor PD-L1: Emerging Genomic Biomarkers for Checkpoint Inhibitor Immunotherapy

Despite the success of immune checkpoint blockade as a strategy for activating an antitumor immune response and promoting cancer regression, only a subset of patients have durable clinical benefit. Efforts are ongoing to identify robust biomarkers that can effectively predict treatment response to immune checkpoint inhibitors (ICIs). Although PD-L1 expression is useful for stratifying patients, it is an imperfect tool. Comprehensive next-generation sequencing platforms that are readily used in clinical practice to identify a tumor's potentially actionable genetic alterations also reveal tumor genomic features, including tumor mutation burden (TMB), that may impact the response to ICIs. High TMB enhances tumor immunogenicity through increased numbers of tumor neoantigens that may promote an immune response. Defective DNA repair, leading to microsatellite instability, is an endogenous mechanism for increased tumor TMB that augments response to anti-PD-1 blockade. Alternatively, DNA damage from exogenous factors is responsible for high TMB seen in melanoma, lung cancer, and urothelial carcinoma, among tumor subtypes with higher response rates to ICIs. In this review, we summarize data supporting the use of TMB as a biomarker as well as its known limitations. We also highlight specific tumor suppressor genes and oncogenes that are under investigation as biomarkers for ICI response and resistance. Efforts are ongoing to delineate which genomic tumor characteristics can eventually be utilized in clinical practice to ascertain the benefit of ICIs for an individual patient.

Activity of Birinapant, a SMAC Mimetic Compound, Alone or in Combination in NSCLCs With Different Mutations

Liver kinase B1 (LKB1/STK11) is the second tumor suppressor gene most frequently mutated in non-small-cell lung cancer (NSCLC) and its activity is impaired in about half KRAS-mutated NSCLCs. Nowadays, no effective therapies are available for patients having these mutations. To highlight new vulnerabilities of this subgroup of tumors exploitable to design specific therapies we screened an US FDA-approved drug library using an isogenic system of wild-type (WT) or deleted LKB1. Among eight hit compounds, Birinapant, an inhibitor of the Inhibitor of Apoptosis Proteins (IAPs), was the most active compound in LKB1-deleted clone only compared to its LKB1 WT counterpart. We validated the Birinapant cells response and its mechanism of action to be dependent on LKB1 deletion. Indeed, we demonstrated the ability of this compound to induce apoptosis, through activation of caspases in the LKB1-deleted clone only. Expanding our results, we found that the presence of KRAS mutations could mediate Birinapant resistance in a panel of NSCLC cell lines. The combination of Birinapant with Ralimetinib, inhibitor of p38α, restores the sensitivity of LKB1- and KRAS-mutated cell lines to the IAP inhibitor Birinapant. Our study shows how the use of Birinapant could be a viable therapeutic option for patients with LKB1-mutated NSCLCs. In addition, combination of Birinapant and a KRAS pathway inhibitor, as Ralimetinib, could be useful for patients with LKB1 and KRAS-mutated NSCLC.

Collective invasion of glioma cells through OCT1 signalling and interaction with reactive astrocytes after surgery

Glioblastoma multiforme (GBM) is the most aggressive form of brain cancer with a short median survival time. GBM is characterized by the hallmarks of aggressive proliferation and cellular infiltration of normal brain tissue. miR-451 and its downstream molecules are known to play a pivotal role in regulation of the balance of proliferation and aggressive invasion in response to metabolic stress in the tumour microenvironment (TME). Surgery-induced transition in reactive astrocyte populations can play a significant role in tumour dynamics. In this work, we develop a multi-scale mathematical model of miR-451-LKB1-AMPK-OCT1-mTOR pathway signalling and individual cell dynamics of the tumour and reactive astrocytes after surgery. We show how the effects of fluctuating glucose on tumour cells need to be reprogrammed by taking into account the recent history of glucose variations and an AMPK/miR-451 reciprocal feedback loop. The model shows how variations in glucose availability significantly affect the activity of signalling molecules and, in turn, lead to critical cell migration. The model also predicts that microsurgery of a primary tumour induces phenotypical changes in reactive astrocytes and stem cell-like astrocytes promoting tumour cell proliferation and migration by Cxcl5. Finally, we investigated a new anti-tumour strategy by Cxcl5-targeting drugs. This article is part of the theme issue 'Multi-scale analysis and modelling of collective migration in biological systems'.

Emerging Therapeutic Implications of STK11 Mutation: Case Series

STK11 was first recognized as a tumor suppressor gene in the late 1990s based on linkage analysis of patients with Peutz-Jeghers syndrome. STK11 encodes LKB1, an intracellular serine-threonine kinase involved in cellular metabolism, cell polarization, regulation of apoptosis, and DNA damage response. Recurrent somatic loss-of-function mutations occur in multiple cancer types, most notably in 13% of lung adenocarcinomas. Recent reports indicate that KRAS-mutant non-small cell lung cancers harboring co-mutations in STK11 do not respond to PD-1 axis inhibitors. We present three patients with STK11-mutated tumors and discuss the proposed mechanisms by which germline and somatic alterations in STK11 promote carcinogenesis, potential approaches for therapeutic targeting, and the new data on resistance to immune checkpoint inhibitors. KEY POINTS: STK11 is a tumor suppressor gene, and loss-of-function mutations are oncogenic, due at least in part to loss of AMPK regulation of mTOR and HIF-1-α. Clinical trials are under way, offering hope to patients whose STK11-mutated tumors are refractory and/or have progressed on chemotherapeutic regimens. Whether gastrointestinal cancers with STK11 loss of function will show the same outcome and potential refractoriness to immune therapy that were reported for lung cancer is unknown. However, physicians managing such patients should consider the experience in lung cancer, particularly outside the context of a clinical trial. In the CheckMate-057 trial lung tumors harboring co-mutations in KRAS and STK11 had an inferior response to PD-1 axis inhibitors. Coupled with the observation that STK11-mutated tumors were found to have a cold immune microenvironment regardless of KRAS status, the conclusion could extend to KRAS wild-type tumors with STK11 mutation. Current data suggest that the use of PD-1 axis inhibitors may be ill advised in the presence of STK11 mutation.

Repression of LKB1 by miR-17∼92 Sensitizes MYC-Dependent Lymphoma to Biguanide Treatment

Cancer cells display metabolic plasticity to survive stresses in the tumor microenvironment. Cellular adaptation to energetic stress is coordinated in part by signaling through the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathway. Here, we demonstrate that miRNA-mediated silencing of LKB1 confers sensitivity of lymphoma cells to mitochondrial inhibition by biguanides. Using both classic (phenformin) and newly developed (IM156) biguanides, we demonstrate that elevated miR-17∼92 expression in Myc+ lymphoma cells promotes increased apoptosis to biguanide treatment in vitro and in vivo. This effect is driven by the miR-17-dependent silencing of LKB1, which reduces AMPK activation in response to complex I inhibition. Mechanistically, biguanide treatment induces metabolic stress in Myc+ lymphoma cells by inhibiting TCA cycle metabolism and mitochondrial respiration, exposing metabolic vulnerability. Finally, we demonstrate a direct correlation between miR-17∼92 expression and biguanide sensitivity in human cancer cells. Our results identify miR-17∼92 expression as a potential biomarker for biguanide sensitivity in malignancies.

Effect of Metformin Plus Tyrosine Kinase Inhibitors Compared With Tyrosine Kinase Inhibitors Alone in Patients With Epidermal Growth Factor Receptor-Mutated Lung Adenocarcinoma: A Phase 2 Randomized Clinical Trial

IMPORTANCE

Metformin hydrochloride is emerging as a repurposed anticancer drug. Preclinical and retrospective studies have shown that it improves outcomes across a wide variety of neoplasms, including lung cancer. Particularly, evidence is accumulating regarding the synergistic association between metformin and epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs).

OBJECTIVE

To assess the progression-free survival (PFS) in patients with advanced lung adenocarcinoma who received treatment with EGFR-TKIs plus metformin compared with those who received EGFR-TKIs alone.

DESIGN, SETTING, AND PARTICIPANTS

Open-label, randomized, phase 2 trial conducted at the Instituto Nacional de Cancerología (INCan), Mexico City, Mexico. Eligible patients were 18 years or older, had histologically confirmed stage IIIB-IV lung adenocarcinoma with an activating EGFR mutation.

INTERVENTIONS

Patients were randomly allocated to receive EGFR-TKIs (erlotinib hydrochloride, afatinib dimaleate, or gefitinib at standard dosage) plus metformin hydrochloride (500 mg twice a day) or EGFR-TKIs alone. Treatment was continued until occurrence of intolerable toxic effects or withdrawal of consent.

MAIN OUTCOMES AND MEASURES

The primary outcome was PFS in the intent-to-treat population. Secondary outcomes included objective response rate, disease control rate, overall survival (OS), and safety.

RESULTS

Between March 31, 2016, and December 31, 2017, a total of 139 patients (mean [SD] age, 59.4 [12.0] years; 65.5% female) were randomly assigned to receive EGFR-TKIs (n = 70) or EGFR-TKIs plus metformin (n = 69). The median PFS was significantly longer in the EGFR-TKIs plus metformin group (13.1; 95% CI, 9.8-16.3 months) compared with the EGFR-TKIs group (9.9; 95% CI, 7.5-12.2 months) (hazard ratio, 0.60; 95% CI, 0.40-0.94; P = .03). The median OS was also significantly longer for patients receiving the combination therapy (31.7; 95% CI, 20.5-42.8 vs 17.5; 95% CI, 11.4-23.7 months; P = .02).

CONCLUSIONS AND RELEVANCE

To our knowledge, this is the first study to prospectively show that the addition of metformin to standard EGFR-TKIs therapy in patients with advanced lung adenocarcinoma significantly improves PFS. These results justify the design of a phase 3, placebo-controlled study.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03071705.

Effects of metformin on tumor hypoxia and radiotherapy efficacy: a [18F]HX4 PET imaging study in colorectal cancer xenografts

Background

In a colorectal cancer xenograft model, we investigated the therapeutic effect of metformin on tumor hypoxia with [¹⁸F]flortanidazole ([¹⁸F]HX4) small-animal positron emission tomography (μPET). We also assessed the additive effect of metformin on long-term radiotherapy outcome and we studied the potential of [¹⁸F]HX4 as a predictive and/or prognostic biomarker within this setup.

Methods

Colo205-bearing mice (n = 40) underwent a baseline [¹⁸F]HX4 hypoxia μPET/computed tomography (CT) scan. The next day, mice received 100 mg/kg metformin or saline intravenously (n = 20/group) and [¹⁸F]HX4 was administered intravenously 30 min later, whereupon a second μPET/CT scan was performed to assess changes in tumor hypoxia. Two days later, mice were further divided into four therapy groups (n = 10/group): control (1), metformin (2), radiotherapy (3), and metformin + radiotherapy, i.e., combination (4). Then, they received a second dose of metformin (groups 2 and 4) or saline (groups 1 and 3), followed by a single radiotherapy dose of 15 Gy (groups 3 and 4) or sham irradiation (groups 1 and 2) 30 min later. Tumor growth was followed three times a week by caliper measurements to assess the therapeutic outcome.

Results

[¹⁸F]HX4 uptake decreased in metformin-treated tumors with a mean intratumoral reduction in [¹⁸F]HX4 tumor-to-background ratio (TBR) from 2.53 ± 0.30 to 2.28 ± 0.26 (p = 0.04), as opposed to saline treatment (2.56 ± 0.39 to 3.08 ± 0.39; p = 0.2). The median tumor doubling time (TDT) was 6, 8, 41, and 43 days in the control, metformin, radiotherapy and combination group, respectively (log-rank p < 0.0001), but no metformin-specific therapy effects could be detected. Baseline [¹⁸F]HX4 TBR was a negative prognostic biomarker for TDT (hazard ratio, 2.39; p = 0.02).

Conclusions

Metformin decreased [¹⁸F]HX4 uptake of Colo205-tumors, but had no additive effect on radiotherapy efficacy. Nevertheless, [¹⁸F]HX4 holds promise as a prognostic imaging biomarker.

The Role of AMPK/mTOR Modulators in the Therapy of Acute Myeloid Leukemia

Differentiation therapy of acute promyelocytic leukemia with all-trans retinoic acid represents the most successful pharmacological therapy of acute myeloid leukemia (AML). Numerous studies demonstrate that drugs that inhibit mechanistic target of rapamycin (mTOR) and activate AMP-kinase (AMPK) have beneficial effects in promoting differentiation and blocking proliferation of AML. Most of these drugs are already in use for other purposes; rapalogs as immunosuppressants, biguanides as oral antidiabetics, and 5-amino-4-imidazolecarboxamide ribonucleoside (AICAr, acadesine) as an exercise mimetic. Although most of these pharmacological modulators have been widely used for decades, their mechanism of action is only partially understood. In this review, we summarize the role of AMPK and mTOR in hematological malignancies and discuss the possible role of pharmacological modulators in proliferation and differentiation of leukemia cells.

Multi-omic molecular comparison of primary versus metastatic pancreatic tumours

BACKGROUND

Molecular profiling is increasingly used to match patients with metastatic cancer to targeted therapies, but obtaining a high-quality biopsy specimen from metastatic sites can be difficult.

METHODS

Patient samples were received by Perthera to coordinate genomic, proteomic and/or phosphoproteomic testing, using a specimen from either the primary tumour or a metastatic site. The relative frequencies were compared across specimen sites to assess the potential limitations of using a primary tumour sample for clinical decision support.

RESULTS

No significant differences were identified at the gene or pathway level when comparing genomic alterations between primary and metastatic lesions. Site-specific trends towards enrichment of MYC amplification in liver lesions, STK11 mutations in lung lesions and ATM and ARID2 mutations in abdominal lesions were seen, but were not statistically significant after false-discovery rate correction. Comparative analyses of proteomic results revealed significantly elevated expression of ERCC1 and TOP1 in metastatic lesions.

CONCLUSIONS

Tumour tissue limitations remain a barrier to precision oncology efforts, and these real-world data suggest that performing molecular testing on a primary tumour specimen could be considered in patients with pancreatic adenocarcinoma who do not have adequate tissue readily available from a metastatic site.

Tumor Suppressor LKB1 inhibits both the mRNA Expression and the Amplification of hTERC by the Phosphorylation of YAP in Lung Cancer Cells

Liver kinase B1 (LKB1) is a critical tumor suppressor that is frequently mutated in human cancers. LKB1 has serine/threonine protein kinase activity, which regulates gene expression by phosphorylation of Yes-Associated protein (YAP). The phosphorylation-dependent YAP shuttling is critically important intracellular mechanism in the Hippo pathway. In our previous study, we found that the amplification of hTERC was significant higher in the bronchial brushing cells of patients with lung cancer, however, the underlying molecular mechanism is not clear. In this study, we showed that LKB1 overexpression could phosphorylate YAP and promoted its nuclear rejection. Silencing LKB1 could dephosphorylate YAP and promoted its entry into the nucleus. Here, we found that LKB1 inhibited the mRNA expression and the amplification of hTERC. YAP further up-regulated hTERC at mRNA and gene amplification levels. Therefore, we suggest that LKB1 may inhibit the expression and amplification of hTERC through the axis of LKB1-pYAP(YAP)-hTERC.

Bioluminescent-based imaging and quantification of glucose uptake in vivo

Glucose is a major source of energy for most living organisms, and its aberrant uptake is linked to many pathological conditions. However, our understanding of disease-associated glucose flux is limited owing to the lack of robust tools. To date, positron-emission tomography imaging remains the gold standard for measuring glucose uptake, and no optical tools exist for non-invasive longitudinal imaging of this important metabolite in in vivo settings. Here, we report the development of a bioluminescent glucose-uptake probe for real-time, non-invasive longitudinal imaging of glucose absorption both in vitro and in vivo. In addition, we demonstrate that the sensitivity of our method is comparable with that of commonly used 18F-FDG-positron-emission-tomography tracers and validate the bioluminescent glucose-uptake probe as a tool for the identification of new glucose transport inhibitors. The new imaging reagent enables a wide range of applications in the fields of metabolism and drug development.

Transcriptional and metabolic rewiring of colorectal cancer cells expressing the oncogenic KRASG13D mutation

Background

Activating mutations in KRAS frequently occur in colorectal cancer (CRC) patients, leading to resistance to EGFR-targeted therapies.

Methods

To better understand the cellular reprogramming which occurs in mutant KRAS cells, we have undertaken a systems-level analysis of four CRC cell lines which express either wild type (wt) KRAS or the oncogenic KRAS^G13D allele (mtKRAS).

Results

RNAseq revealed that genes involved in ribosome biogenesis, mRNA translation and metabolism were significantly upregulated in mtKRAS cells. Consistent with the transcriptional data, protein synthesis and cell proliferation were significantly higher in the mtKRAS cells. Targeted metabolomics analysis also confirmed the metabolic reprogramming in mtKRAS cells. Interestingly, mtKRAS cells were highly transcriptionally responsive to EGFR activation by TGFα stimulation, which was associated with an unexpected downregulation of genes involved in a range of anabolic processes. While TGFα treatment strongly activated protein synthesis in wtKRAS cells, protein synthesis was not activated above basal levels in the TGFα-treated mtKRAS cells. This was likely due to the defective activation of the mTORC1 and other pathways by TGFα in mtKRAS cells, which was associated with impaired activation of PKB signalling and a transient induction of AMPK signalling.

Conclusions

We have found that mtKRAS cells are substantially rewired at the transcriptional, translational and metabolic levels and that this rewiring may reveal new vulnerabilities in oncogenic KRAS CRC cells that could be exploited in future.

LKB1 as a Gatekeeper of Hepatocyte Proliferation and Genomic Integrity during Liver Regeneration

Liver kinase B1 (LKB1) is involved in several biological processes and is a key regulator of hepatic metabolism and polarity. Here, we demonstrate that the master kinase LKB1 plays a dual role in liver regeneration, independently of its major target, AMP-activated protein kinase (AMPK). We found that the loss of hepatic Lkb1 expression promoted hepatocyte proliferation acceleration independently of metabolic/energetic balance. LKB1 regulates G₀/G₁ progression, specifically by controlling epidermal growth factor receptor (EGFR) signaling. Furthermore, later in regeneration, LKB1 controls mitotic fidelity. The deletion of Lkb1 results in major alterations to mitotic spindle formation along the polarity axis. Thus, LKB1 deficiency alters ploidy profile at late stages of regeneration. Our findings highlight the dual role of LKB1 in liver regeneration, as a guardian of hepatocyte proliferation and genomic integrity.