Mutant KRAS-driven cancers depend on PTPN11/SHP2 phosphatase

Evolution of computational techniques against various KRAS mutants in search for therapeutic drugs: a review article

KRAS was (Kirsten rat sarcoma viral oncogene homolog) revealed as an important target in current therapeutic cancer research because alteration of RAS (rat sarcoma viral oncogene homolog) protein has a critical role in malignant modification, tumor angiogenesis, and metastasis. For cancer treatment, designing competitive inhibitors for this attractive target was difficult. Nevertheless, computational investigations of the protein's dynamic behavior displayed the existence of temporary pockets that could be used to design allosteric inhibitors. The last decade witnessed intensive efforts to discover KRAS inhibitors. In 2021, the first KRAS G12C covalent inhibitor, AMG 510, received FDA (Food and drug administration) approval as an anticancer medication that paved the path for future treatment strategies against this target. Computer-aided drug designing discovery has long been used in drug development research targeting different KRAS mutants. In this review, the major breakthroughs in computational methods adapted to discover novel compounds for different mutations have been discussed. Undoubtedly, virtual screening and molecular dynamic (MD) simulation and molecular docking are the most considered approach, producing hits that can be employed in subsequent refinements. After comprehensive analysis, Afatinib and Quercetin were computationally identified as hits in different publications. Several authors conducted covalent docking studies with acryl amide warheads groups containing inhibitors. Future studies are needed to demonstrate their true potential. In-depth studies focusing on various allosteric pockets demonstrate that the switch I/II pocket is a suitable site for drug designing. In addition, machine learning and deep learning based approaches provide new insights for developing anti-KRAS drugs. We believe that this review provides extensive information to researchers globally and encourages further development in this particular area of research.

19Fluorine-MRI Based Longitudinal Immuno-Microenvironment-Monitoring for Pancreatic Cancer

BACKGROUND

Pancreatic cancer has a poor prognosis. Targeting Kirsten Rat Sarcoma (KRAS) mutation and its related pathways may enhance immunotherapy efficacy. While in vivo monitoring of therapeutic response and immune cell migration remains challenging, Fluorine-19 MRI (19F MRI) may allow noninvasive longitudinal imaging of immune cells.

PURPOSE

Evaluating the potential of 19F MRI for monitoring changes in the tumor immune microenvironment, in response to combined SHP2/MEK inhibition.

STUDY TYPE

Pre-clinical animal study.

ANIMAL MODEL

Murine genetically engineered pancreatic cancer model (N = 20, both sexes).

FIELD STRENGTH/SEQUENCE

9.4-T, two-dimensional multi-slice Rapid Acquisition with Relaxation Enhancement sequence. Intravenous injection of 19F-perfluorocarbon (PFC) nanoparticles.

ASSESSMENT

Upon tumor detection by conventional 1H MRI screening, 19F MRI was performed in mice 24 hours after PFC nanoparticle administration. Animals were randomly assigned to four treatment groups: allosteric Src-homology-2-containing protein tyrosine phosphatase 2 (SHP2) inhibitor SHP099, the mitogen-activated extracellular signal-regulated kinase 1/2 (MEK1/2) inhibitor Trametinib, the combination of both, or a vehicle control (4 to 6 mice each group), administered every other day per oral gavage. 1H and 19F MRI was repeated 7 days and 14 days later. Pancreatic immune cell infiltrates were analyzed by flow cytometry and multiplex immunohistofluorescence (mIHF) upon sacrifice.

STATISTICAL TESTS

Independent t-tests and one-way analysis of variance.

RESULTS

19F MRI revealed continuous decrease of PFC-signals in tumors from vehicle controls (100%, 80%, and 74% on days 0, 7, and 14, respectively), contrasting with stable or increasing signals under KRAS-pathway-directed treatment. MEK inhibition showed 100%, 152%, and 84% and dual SHP2/MEK1/2 inhibition demonstrated signals of 100%, 134%, and 100% on days 0, 7, 14, respectively. mIHF analyses indicated CD11b+ macrophages/monocytes as primary contributors to the observed 19F MRI signal differences.

DATA CONCLUSION

19F MRI might provide non-invasive longitudinal estimates for abundance and spatial distribution of CD11b+ macrophages/monocytes in pancreatic cancer.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

Current status and prospects of targeted therapy for cholangiocarcinoma based on molecular characteristics

Cholangiocarcinoma (CCA) is a serious public health issue due to its insidious onset and dismal prognosis. The past few years have witnessed and highlighted the development of understanding and management of CCA. The combination of gemcitabine and cisplatin (GP) chemotherapy regimen with immunotherapy using immune checkpoint inhibitors has been considered the new standard first-line treatment alternative for advanced CCA. Notably, the proportion of patients with advanced CCA with targetable genetic mutations is approximately 40 %, and these patients may be considered for molecularly targeted therapy in the second-line treatment. In this review, we highlight the advances and progress in targeted therapies for advanced CCA, with special attention to data from Asian populations, including Chinese. In addition, we present in detail the phosphatase tension homolog (PTEN), a novel biomarker for both of first-line chemotherapy and second-line targeted therapy in advanced CCA, and its ability to forecast prognosis in patients with CCA. The mechanisms of rapid resistance to targeted agents warrant further investigation and address in light of the development of new targeted therapies. Precision medicine is gradually playing an increasing role in achieving optimal therapeutic outcomes.

RAS mutation-specific signaling dynamics in response to paralog- and state- selective RAS inhibitors

A high therapeutic index (TI), balancing potent oncogenic signaling inhibition in tumor cells with minimal effects on normal cells, is critical for effective cancer therapies. Recent advances have introduced diverse RAS-targeting inhibitors, including mutant-specific inhibitors (e.g., KRAS(G12C) and KRAS(G12D)), as well as paralog- and state-selective inhibitors. Non-mutant-specific RAS inhibition can be accomplished by 1) panRAS-GEF(OFF) inhibitors which inactivate RAS indirectly by inhibiting SHP2 or SOS1, thereby blocking the nucleotide exchange step of RAS activation, 2) direct KRAS(OFF)-selective inhibitors sparing NRAS and HRAS, and 3) panRAS(ON) inhibitors that directly target active RAS, by occluding binding of its effector RAF. However, the signaling inhibition index (SII) - the differential inhibition of oncogenic signaling between RAS-mutant (RAS(MUT)) and normal cells - remains poorly defined for these approaches. In this study, we evaluated the SII of state- and paralog-selective RAS inhibitors across diverse RAS-mutant (RAS(MUT)) and RAS-wild-type (RAS(WT)) models. PanRAS-GEF(OFF) inhibitors exhibited neutral or negative SII, with comparable or reduced MAPK suppression in KRAS(G12X) cells relative to RAS(WT) cells. KRAS(G13D) models showed low sensitivity (negative SII) to panRAS-GEF(OFF) inhibitors, particularly in the context of NF1 loss. Combination treatments with SHP2 and MEK inhibitors resulted in low SII, as pathway suppression was similar in RAS(MUT) and RAS(WT) cells. Furthermore, RAS(Q61X) models were resistant to combined SHP2 inhibitor+MEK inhibitor due to dual mechanisms: MEK inhibitor-induced NRAS(Q61X) reactivation and RAS(MUT)-induced SHP2 conformations impairing inhibitor binding. Overall, panRAS-GEF(OFF) inhibitors exhibited the lowest SII. PanKRAS(OFF) inhibitors demonstrated a higher SII, while panRAS(ON) inhibitors displayed broader activity but relatively narrow SII. We observed that tumors that were sensitive to RAS(MUT)-specific inhibitors, were also sensitive to the state-selective RAS inhibitors (OFF, or ON). In fact, all RAS inhibitors (mutant-specific and state- or paralog-selective) were active in the same portion of RAS(MUT) models, while the majority of RAS(MUT) cell lines were insensitive to all of them. These findings reveal significant SII variability among RAS-targeted inhibitors, depending on the specific RAS driver mutation and cell context and underscore the importance of incorporating SII considerations into the design and clinical application of RAS-targeted therapies to improve therapeutic outcomes.

Main points

PanRAS-GEF(OFF) inhibitors have limited SII and effectiveness: The Signaling Inhibition Index (SII) - i.e. the differential inhibition of oncogenic signaling between tumor and normal cells - was neutral or negative for panRAS-GEF(OFF) inhibitors, with comparable or reduced MAPK suppression in KRAS(G12X) mutant versus RAS(WT) cells. KRAS(G13D) models showed reduced sensitivity, particularly with NF1 loss. SHP2+MEK inhibitor combinations also had low SII, with RAS(Q61X) models demonstrating resistance due to NRAS(Q61X) reactivation and impaired SHP2 inhibitor binding.PanKRAS(OFF) selective inhibitors have higher SII than panRAS-GEF(OFF) inhibitors: panKRAS(OFF)-selective inhibitors have a higher SII compared to panRAS-GEF(OFF) inhibitors, offering better tumor-versus-normal cell selectivity.PanRAS(ON) inhibitors have broad but modest SII: While panRAS(ON) inhibitors displayed a broader activity profile, their ability to selectively inhibit mutant RAS signaling over normal cells remained relatively narrow (low SII).Most KRAS-mutant tumors will be insensitive to any single RAS-targeted inhibitor: State- and paralog-selective inhibitors have enhanced activity in the same RAS-MUT cancer models that are also sensitive to RAS-MUT-specific inhibitors, suggesting that most KRAS-MUT tumors will not respond uniformly to any one RAS-targeting inhibitor.SII varies across RAS inhibitors, necessitating tailored therapeutic strategies: The effectiveness of paralog- and state-selective inhibitors depends on specific RAS mutations and cell context, highlighting the need to integrate SII considerations into the development and clinical application of RAS-targeted therapies.

PTPN23-dependent activation of PI3KC2α is a therapeutic vulnerability of BRAF-mutant cancers

BRAF mutations drive initiation and progression of various tumors. While BRAF inhibitors are effective in BRAF-mutant melanoma patients, intrinsic or acquired resistance to these therapies is common. Here, we identify non-receptor-type protein tyrosine phosphatase 23 (PTPN23) as an alternative effective target in BRAF-mutant cancer cells. Silencing PTPN23 selectively kills BRAF-mutant melanoma cells but not those with wild-type BRAF. Mechanistically, PTPN23, a catalytically inactive phosphatase, intriguingly induces WNK3-mediated phosphorylation of phosphoinositide 3-kinase class II alpha (PI3KC2α) at serine 329, enhancing its catalytic activity. This activation promotes production of PI(3,4)P2 and subsequent AKT2 activation at endosomes to support cell survival. Genetic or pharmacological targeting of the PTPN23-PI3KC2α-AKT2 signaling axis, alone or in combination with BRAF inhibitors, effectively inhibits the growth of BRAF-mutant melanoma and other cancers in vitro and in vivo. We also demonstrate that melanocyte-specific knockout of PTPN23 significantly inhibits BRAFV600E-driven melanomagenesis. Altogether, our findings demonstrate that targeting PTPN23/PI3KC2α offers a new and viable therapeutic strategy for BRAF-mutant cancers.

Recent advances in targeted degradation in the RAS pathway

RAS (rat sarcoma) is one of the most frequently mutated gene families in cancer, encoding proteins classified as small GTPases. Mutations in RAS proteins result in abnormal activation of the RAS signaling pathway, a key driver in the initiation and progression of various malignancies. Consequently, targeting RAS proteins and the RAS signaling pathway has become a critical strategy in anticancer therapy. While RAS was historically considered an "undruggable" target, recent breakthroughs have yielded inhibitors specifically targeting KRASG12C and KRASG12D mutations, which have shown clinical efficacy in patients. However, these inhibitors face limitations due to rapid acquired resistance and the toxic effects of combination therapies in clinical settings. Targeted protein degradation (TPD) strategies, such as PROTACs and molecular glues, provide a novel approach by selectively degrading RAS proteins, or their upstream and downstream regulatory factors, to block aberrant signaling pathways. These degraders offer a promising alternative to traditional inhibitors by potentially circumventing resistance and enhancing therapeutic precision. This review discusses recent advancements in RAS pathway degraders, with an emphasis on targeting RAS mutations as well as their upstream regulators and downstream effectors for potential cancer treatments.

KRAS Mutations in Cancer: Understanding Signaling Pathways to Immune Regulation and the Potential of Immunotherapy

The Kirsten rat sarcoma viral oncogene homologue (KRAS) mutation is one of the most prevailing mutations in various tumors and is difficult to cure. Long-term proliferation in carcinogenesis is primarily initiated by oncogenic KRAS-downstream signaling. Recent research suggests that it also activates the autocrine effect and interplays the tumor microenvironment (TME). Here, we discuss the emerging research, including KRAS mutations to immune evasion in TME, which induce immunological modulation that promotes tumor development. This review gives an overview of the existing knowledge of the underlying connection between KRAS mutations and tumor immune modulation. It also addresses the mechanisms to reduce the effect of oncogenes on the immune system and recent advances in clinical trials for immunotherapy in KRAS-mutated cancers.

KRAS inhibitors in drug resistance and potential for combination therapy

Kirsten Rat Sarcoma (KRAS) is a potent target for cancer therapy because it acts as a signaling hub, engaging in various signaling pathways and regulating a number of cellular functions like cell differentiation, proliferation, and survival. Recently, an emergency approval from the US-FDA has been issued for KRASG12C inhibitors (sotorasib and adagrasib) for metastatic lung cancer treatment. However, clinical studies on covalent KRASG12C inhibitors have rapidly confronted resistance in patients. Many methods are being assessed to overcome this resistance, along with various combinatorial clinical studies that are in process. Moreover, because KRASG12D and KRASG12V are more common than KRASG12C, focus must be placed on the therapeutic strategies for this type of patient, along with sustained efforts in research on these targets. In the present review, we try to focus on various strategies to overcome rapid resistance through the use of combinational treatments to improve the activity of KRASG12C inhibitors.

KRAS inhibitors: resistance drivers and combinatorial strategies

In 1982, the RAS genes HRAS and KRAS were discovered as the first human cancer genes, with KRAS later identified as one of the most frequently mutated oncogenes. Yet, it took nearly 40 years to develop clinically effective inhibitors for RAS-mutant cancers. The discovery in 2013 by Shokat and colleagues of a druggable pocket in KRAS paved the way to FDA approval of the first covalently binding KRASG12C inhibitors, sotorasib and adagrasib, in 2021 and 2022, respectively. However, rather than marking the end of a successful assault on the Mount Everest of cancer research, this landmark only revealed new challenges in RAS drug discovery. In this review, we highlight the progress on defining resistance mechanisms and developing combination treatment strategies to improve patient responses to KRAS therapies.

KRASG 12C-inhibitor-based combination therapies for pancreatic cancer: insights from drug screening

Pancreatic ductal adenocarcinoma (PDAC) has limited treatment options, emphasizing the urgent need for effective therapies. The predominant driver in PDAC is mutated KRAS proto-oncogene, KRA, present in 90% of patients. The emergence of direct KRAS inhibitors presents a promising avenue for treatment, particularly those targeting the KRASG12C mutated allele, which show encouraging results in clinical trials. However, the development of resistance necessitates exploring potent combination therapies. Our objective was to identify effective KRASG12C-inhibitor combination therapies through unbiased drug screening. Results revealed synergistic effects with son of sevenless homolog 1 (SOS1) inhibitors, tyrosine-protein phosphatase non-receptor type 11 (PTPN11)/Src homology region 2 domain-containing phosphatase-2 (SHP2) inhibitors, and broad-spectrum multi-kinase inhibitors. Validation in a novel and unique KRASG12C-mutated patient-derived organoid model confirmed the described hits from the screening experiment. Our findings propose strategies to enhance KRASG12C-inhibitor efficacy, guiding clinical trial design and molecular tumor boards.

Synergistic Inhibition of Drug Resistant KRAS Mutant Non-Small Cell Lung Cancer by Co-Targeting AXL and SRC

BACKGROUND/OBJECTIVES

KRAS-mutated NSCLC has been targeted using monoclonal antibody (mAb) or tyrosine kinase inhibitor (TKI) therapies. However, in time, these mutations appear to develop resistance against the targeted antibodies and TKI treatments. One possible explanation is the activation of pro apoptotic pathways through the AXL-SRC-Akt axis. In this study, we identify AXL as the bypass resistant gene and investigate its role with KRAS and SRC activity.

METHODS

In this study, we use Dasatinib and SGI-7079 to co-inhibit SRC and AXL respectively. In vitro studies were conducted using four cell lines, and AXL suppression was achieved using siRNA and in CRISPR-Cas9 mediated knockout models. Subsequently, we studied gene-protein expression analysis using Western blot, apoptotic markers using a cytochrome release assay and cytotoxicity using an MTT assay. A549 xenografts were studied for in vivo validation of our proposed hypothesis.

RESULTS

The results suggest that dual inhibition of AXL and SRC significantly reversed this resistance, both in in vivo and in vitro studies.

CONCLUSIONS

Co-inhibition of AXL and SRC synergistically reduced KRAS activity and induced apoptosis in NSCLC.

Optimization of SHP2 allosteric inhibitors with novel tail heterocycles and their potential as antitumor therapeutics

SHP2, a non-receptor protein tyrosine phosphatase involved in cancers, plays a pivotal role in numerous cellular signaling cascades, including the MAPK and PD-L1/PD-1 pathways. Although several SHP2 allosteric inhibitors have already entered clinical trials, none have been approved to date. Therefore, the development of new SHP2 allosteric inhibitors with improved efficacy is urgently required. Herein, we report the optimization of tail heterocycles in SHP2 allosteric inhibitors using a structure-based drug design strategy. Four series of compounds with different tail skeletons were synthesized, among which D13 showed notable inhibitory activity (IC50 = 1.2 μM) against SHP2. Molecular docking and binding studies indicated that the newly synthesized compounds exerted enzymatic inhibitory effects by directly binding to SHP2 with relatively slow dissociation rates. At the cellular level, Huh7 cells demonstrated heightened sensitivity to the novel SHP2 inhibitors, and D13 exhibited superior antiproliferative activity (IC50 = 38 μM) by arresting G0/G1 cell cycle, facilitating cell apoptosis and suppressing the MAPK signaling pathway. In the in vivo study, D13 displayed significant antitumor activity in a Huh7 xenograft model and possessed favorable druggability with acceptable oral bioavailability (F = 54 %) and half-life (t1/2 = 10.57 h). Collectively, this study lays a robust foundation for further optimization of the tail heterocycle skeleton in SHP2 allosteric inhibitors.

Socci N, Bale TA, Davis C, Dixon SAH, Zhang C, Wade Clapp D, Neel BG, Parada LF. Hydroxychloroquine prevents resistance and potentiates the antitumor effect of SHP2 inhibition in NF1-associated malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas and the primary cause of mortality in patients with neurofibromatosis type 1 (NF1). These malignancies develop within preexisting benign lesions called plexiform neurofibromas (PNs). PNs are solely driven by biallelic NF1 loss eliciting RAS pathway activation, and they respond favorably to MEK inhibitor therapy. MPNSTs harbor additional mutations and respond poorly to MEK inhibition. Our analysis of genetically engineered and orthotopic patient-derived xenograft MPNST models indicates that MEK inhibition has poor antitumor efficacy. By contrast, upstream inhibition of RAS through the protein-tyrosine phosphatase SHP2 reduced downstream signaling and suppressed NF1 MPNST growth, although resistance eventually emerged. To investigate possible mechanisms of acquired resistance, kinomic analyses of resistant tumors were performed, and data analysis identified enrichment of activated autophagy pathway protein kinases. Combining SHP2 inhibition with hydroxychloroquine (HQ) resulted in durable responses in NF1 MPNSTs in both genetic and orthotopic xenograft mouse models. Our studies could be rapidly translated into a clinical trial to evaluate SHP2 inhibition in conjunction with HQ as a unique treatment approach for NF1 MPNSTs.

SOS1 Inhibition Enhances the Efficacy of KRASG12C Inhibitors and Delays Resistance in Lung Adenocarcinoma

The clinical effectiveness of KRASG12C inhibitors (G12Ci) is limited both by intrinsic and acquired resistance, necessitating the development of combination approaches. Here, we identified targeting proximal receptor tyrosine kinase signaling using the SOS1 inhibitor (SOS1i) BI-3406 as a strategy to improve responses to G12Ci treatment. SOS1i enhanced the efficacy of G12Ci and limited rebound receptor tyrosine kinase/ERK signaling to overcome intrinsic/adaptive resistance, but this effect was modulated by SOS2 protein levels. G12Ci drug-tolerant persister (DTP) cells showed up to a 3-fold enrichment of tumor-initiating cells (TIC), suggestive of a sanctuary population of G12Ci-resistant cells. SOS1i resensitized DTPs to G12Ci and inhibited G12C-induced TIC enrichment. Co-mutation of the tumor suppressor KEAP1 limited the clinical effectiveness of G12Ci, and KEAP1 and STK11 deletion increased TIC frequency and accelerated the development of acquired resistance to G12Ci, consistent with clinical G12Ci resistance seen with these co-mutations. Treatment with SOS1i both delayed acquired G12Ci resistance and limited the total number of resistant colonies regardless of KEAP1 and STK11 mutational status. Together, these data suggest that targeting SOS1 could be an effective strategy to both enhance G12Ci efficacy and prevent G12Ci resistance regardless of co-mutations. Significance: The SOS1 inhibitor BI-3406 both inhibits intrinsic/adaptive resistance and targets drug tolerant persister cells to limit the development of acquired resistance to clinical KRASG12C inhibitors in lung adenocarcinoma cells.

YAP/TAZ mediates resistance to KRAS inhibitors through inhibiting proapoptosis and activating the SLC7A5/mTOR axis

KRAS mutations are frequent in various human cancers. The development of selective inhibitors targeting KRAS mutations has opened a new era for targeted therapy. However, intrinsic and acquired resistance to these inhibitors remains a major challenge. Here, we found that cancer cells resistant to KRAS G12C inhibitors also display cross-resistance to other targeted therapies, such as inhibitors of RTKs or SHP2. Transcriptomic analyses revealed that the Hippo-YAP/TAZ pathway is activated in intrinsically resistant and acquired-resistance cells. Constitutive activation of YAP/TAZ conferred resistance to KRAS G12C inhibitors, while knockdown of YAP/TAZ or TEADs sensitized resistant cells to these inhibitors. This scenario was also observed in KRAS G12D-mutant cancer cells. Mechanistically, YAP/TAZ protects cells from KRAS inhibitor-induced apoptosis by downregulating the expression of proapoptotic genes such as BMF, BCL2L11, and PUMA, and YAP/TAZ reverses KRAS inhibitor-induced proliferation retardation by activating the SLC7A5/mTORC1 axis. We further demonstrated that dasatinib and MYF-03-176 notably enhance the efficacy of KRAS inhibitors by reducing SRC kinase activity and TEAD activity. Overall, targeting the Hippo-YAP/TAZ pathway has the potential to overcome resistance to KRAS inhibitors.

Targeting SHP1 and SHP2 to suppress tumors and enhance immunosurveillance

The nonreceptor tyrosine phosphatases (PTPS) SHP1 and SHP2 have crucial roles in dephosphorylating an array of substrates involved in pathways comprising receptor tyrosine kinases (RTKs) and immune receptors. This regulation maintains a delicate balance between the activation and inhibition of signal transduction, ensuring appropriate biological outcomes. In this review, we summarize research focused on elucidating the functions of SHP1 and SHP2 in hematopoiesis, immune regulation, and tumor biology, emphasizing recent findings related to cancer-driven immune evasion. Furthermore, we highlight the significant effects of SHP1 and SHP2 inhibitors in enhancing cancer treatment, specifically through the facilitation of chemotherapy and augmentation of immune activation.

Concurrent SOS1 and MEK suppression inhibits signaling and growth of NF1-null melanoma

Neurofibromin (NF1) is a negative regulator of RAS signaling, frequently mutated in cancer. NF1-mutant melanoma is a highly malignant tumor for which targeted therapies are lacking. Here, we use biochemical and pharmacological assays on patient-derived models and isogenic cell lines to identify potential pharmacologic targets, revealing that NF1-null melanomas are dependent on RAS activation and that MEK inhibition relieves ERK-dependent negative feedback, increasing RAS signaling. MEK inhibition with avutometinib abrogates the adaptive rebound in ERK signaling, but the antitumor effects are limited. However, concurrent inhibition of MEK and SOS1 abrogates ERK activation, induces cell death, and suppresses tumor growth. In contrast to the NF1-deficient setting, concurrent SOS1 and SOS2 depletion is required to completely inhibit RAS signaling in NF1 wild-type cells. In sum, our data provide a mechanistic rationale for enhancing the therapeutic efficacy of MEK inhibitors by exploiting the lower residual SOS activity in NF1-null tumor cells.

The SOS1 Inhibitor MRTX0902 Blocks KRAS Activation and Demonstrates Antitumor Activity in Cancers Dependent on KRAS Nucleotide Loading

KRAS is the most frequently mutated oncogene in human cancer and facilitates uncontrolled growth through hyperactivation of the receptor tyrosine kinase (RTK)/mitogen-activated protein kinase (MAPK) pathway. The Son of Sevenless homolog 1 (SOS1) protein functions as a guanine nucleotide exchange factor (GEF) for the RAS subfamily of small GTPases and represents a druggable target in the pathway. Using a structure-based drug discovery approach, MRTX0902 was identified as a selective and potent SOS1 inhibitor that disrupts the KRAS:SOS1 protein-protein interaction to prevent SOS1-mediated nucleotide exchange on KRAS and translates into an anti-proliferative effect in cancer cell lines with genetic alterations of the KRAS-MAPK pathway. MRTX0902 augmented the antitumor activity of the KRAS G12C inhibitor adagrasib when dosed in combination in eight out of 12 KRAS G12C-mutant human non-small cell lung cancer and colorectal cancer xenograft models. Pharmacogenomic profiling in preclinical models identified cell cycle genes and the SOS2 homolog as genetic co-dependencies and implicated tumor suppressor genes (NF1 and PTEN) in resistance following combination treatment. Lastly, combined vertical inhibition of RTK/MAPK pathway signaling by MRTX0902 with inhibitors of EGFR or RAF/MEK led to greater downregulation of pathway signaling and improved antitumor responses in KRAS-MAPK pathway-mutant models. These studies demonstrate the potential clinical application of dual inhibition of SOS1 and KRAS G12C and additional SOS1 combination strategies that will aide in the understanding of SOS1 and RTK/MAPK biology in targeted cancer therapy.

KRAS-Driven Tumorigenesis and KRAS-Driven Therapy in Pancreatic Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is associated with significant morbidity and mortality and is projected to be the second leading cause of cancer-related deaths by 2030. Mutations in KRAS are found in the vast majority of PDAC cases and plays an important role in the development of the disease. KRAS drives tumor cell proliferation and survival through activating the MAPK pathway to drive cell cycle progression and to lead to MYC-driven cellular programs. Moreover, activated KRAS promotes a protumorigenic microenvironment through forming a desmoplastic stroma and by impairing antitumor immunity. Secretion of granulocyte-macrophage colony-stimulating factor and recruitment of myeloid-derived suppressor cells and protumorigenic macrophages results in an immunosuppressive environment while secretion of secrete sonic hedgehog and TGFβ drive fibroblastic features characteristic of PDAC. Recent development of several small molecules to directly target KRAS marks an important milestone in precision medicine. Many molecules show promise in preclinical models of PDAC and in early phase clinical trials. In this review, we discuss the underlying cell intrinsic and extrinsic roles of KRAS in PDAC tumorigenesis, the pharmacologic development of KRAS inhibition, and therapeutic strategies to target KRAS in PDAC.

Towards Targeting Endothelial Rap1B to Overcome Vascular Immunosuppression in Cancer

The vascular endothelium, a specialized monolayer of endothelial cells (ECs), is crucial for maintaining vascular homeostasis by controlling the passage of substances and cells. In the tumor microenvironment, Vascular Endothelial Growth Factor A (VEGF-A) drives tumor angiogenesis, leading to endothelial anergy and vascular immunosuppression-a state where ECs resist cytotoxic CD8+ T cell infiltration, hindering immune surveillance. Immunotherapies have shown clinical promise. However, their effectiveness is significantly reduced by tumor EC anergy. Anti-angiogenic treatments aim to normalize tumor vessels and improve immune cell infiltration. Despite their potential, these therapies often cause significant systemic toxicities, necessitating new treatments. The small GTPase Rap1B emerges as a critical regulator of Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) signaling in ECs. Our studies using EC-specific Rap1B knockout mice show that the absence of Rap1B impairs tumor growth, alters vessel morphology, and increases CD8+ T cell infiltration and activation. This indicates that Rap1B mediates VEGF-A's immunosuppressive effects, making it a promising target for overcoming vascular immunosuppression in cancer. Rap1B shares structural and functional similarities with RAS oncogenes. We propose that targeting Rap1B could enhance therapies' efficacy while minimizing adverse effects by reversing endothelial anergy. We briefly discuss strategies successfully developed for targeting RAS as a model for developing anti-Rap1 therapies.

Advances in SHP2 tunnel allosteric inhibitors and bifunctional molecules

SHP2 is a non-receptor tyrosine phosphatase encoded by PTPN11, which performs the functions of regulating cell proliferation, differentiation, apoptosis, and survival through removing tyrosine phosphorylation and modulating various signaling pathways. The overexpression of SHP2 or its mutations is related to developmental diseases and several cancers. Numerous allosteric inhibitors with striking inhibitory potency against SHP2 allosteric pockets have recently been identified, and several SHP2 tunnel allosteric inhibitors have been applied in clinical trials to treat cancers. However, based on clinical results, the efficacy of single-agent treatments has been proven to be suboptimal. Most clinical trials involving SHP2 inhibitors have adopted drug combination strategies. This review briefly discusses the research progress on SHP2 allosteric inhibitors and pathway-dependent drug combination strategies for SHP2 in cancer therapy. In addition, we summarize the current bifunctional molecules of SHP2 and elaborate on the design and structural optimization strategies of these bifunctional molecules in detail, offering further direction for the research on novel SHP2 inhibitors.

KRAS G12C Inhibitors in the Treatment of Metastatic Colorectal Cancer

KRAS mutations contribute substantially to the overall colorectal cancer burden and have long been a focus of drug development efforts. After a lengthy preclinical road, KRAS inhibition via the G12C allele has finally become a therapeutic reality. Unlike in NSCLC, early studies of KRAS inhibitors in CRC struggled to demonstrate single agent activity. Investigation into these tissue-specific treatment differences has led to a deeper understanding of the complexities of MAPK signaling and the diverse adaptive feedback responses to KRAS inhibition. EGFR reactivation has emerged as a principal resistance mechanism to KRAS inhibitor monotherapy. Thus, the field has pivoted to dual EGFR/KRAS blockade with promising efficacy. Despite significant strides in the treatment of KRAS G12C mutated CRC, new challenges are on the horizon. Alternative RTK reactivation and countless acquired molecular resistance mechanisms have shifted the treatment goalpost. This review focuses on the historical and contemporary clinical strategies of targeting KRAS G12C alterations in CRC and highlights future directions to overcome treatment challenges.

MYC and KRAS cooperation: from historical challenges to therapeutic opportunities in cancer

RAS and MYC rank amongst the most commonly altered oncogenes in cancer, with RAS being the most frequently mutated and MYC the most amplified. The cooperative interplay between RAS and MYC constitutes a complex and multifaceted phenomenon, profoundly influencing tumor development. Together and individually, these two oncogenes regulate most, if not all, hallmarks of cancer, including cell death escape, replicative immortality, tumor-associated angiogenesis, cell invasion and metastasis, metabolic adaptation, and immune evasion. Due to their frequent alteration and role in tumorigenesis, MYC and RAS emerge as highly appealing targets in cancer therapy. However, due to their complex nature, both oncogenes have been long considered "undruggable" and, until recently, no drugs directly targeting them had reached the clinic. This review aims to shed light on their complex partnership, with special attention to their active collaboration in fostering an immunosuppressive milieu and driving immunotherapeutic resistance in cancer. Within this review, we also present an update on the different inhibitors targeting RAS and MYC currently undergoing clinical trials, along with their clinical outcomes and the different combination strategies being explored to overcome drug resistance. This recent clinical development suggests a paradigm shift in the long-standing belief of RAS and MYC "undruggability", hinting at a new era in their therapeutic targeting.

Therapeutic potential of targeting protein tyrosine phosphatases in liver diseases

Protein tyrosine phosphorylation is a post-translational modification that regulates protein structure to modulate demic organisms' homeostasis and function. This physiological process is regulated by two enzyme families, protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). As an important regulator of protein function, PTPs are indispensable for maintaining cell intrinsic physiology in different systems, as well as liver physiological and pathological processes. Dysregulation of PTPs has been implicated in multiple liver-related diseases, including chronic liver diseases (CLDs), hepatocellular carcinoma (HCC), and liver injury, and several PTPs are being studied as drug therapeutic targets. Therefore, given the regulatory role of PTPs in diverse liver diseases, a collated review of their function and mechanism is necessary. Moreover, based on the current research status of targeted therapy, we emphasize the inclusion of several PTP members that are clinically significant in the development and progression of liver diseases. As an emerging breakthrough direction in the treatment of liver diseases, this review summarizes the research status of PTP-targeting compounds in liver diseases to illustrate their potential in clinical treatment. Overall, this review aims to support the development of novel PTP-based treatment pathways for liver diseases.

Design, Synthesis and Antitumor Activity of a Novel Class of SHP2 Allosteric Inhibitors with a Furanyl Amide-Based Scaffold

SHP2 plays a critical role in modulating tumor growth and PD-1-related signaling pathway, thereby serving as an attractive antitumor target. To date, no antitumor drugs targeting SHP2 have been approved, and hence, the search of SHP2 inhibitors with new chemical scaffolds is urgently needed. Herein, we developed a novel SHP2 allosteric inhibitor SDUY038 with a furanyl amide scaffold, demonstrating potent binding affinity (KD = 0.29 μM), enzymatic activity (IC50 = 1.2 μM) and similar binding interactions to SHP099. At the cellular level, SDUY038 exhibited pan-antitumor activity (IC50 = 7-24 μM) by suppressing pERK expression. Furthermore, SDUY038 significantly inhibited tumor growth in both xenograft and organoid models. Additionally, SDUY038 displayed acceptable bioavailability (F = 14%) and half-life time (t1/2 = 3.95 h). Conclusively, this study introduces the furanyl amide scaffold as a novel class of SHP2 allosteric inhibitors, offering promising lead compounds for further development of new antitumor therapies targeting SHP2.

WWP1 inhibition increases SHP2 inhibitor efficacy in colorectal cancer

Protein tyrosine phosphatase SHP2 activates RAS signaling, which is a novel target for colorectal cancer (CRC) therapy. However, SHP2 inhibitor monotherapy is ineffective for metastatic CRC and a combination therapy is required. In this study, we aimed to improve the antitumor efficacy of SHP2 inhibition and try to explore the resistance mechanism of SHP2 inhibitor. Results showed that WWP1 promoted the proliferation of CRC cells. Genetic or pharmacological inhibition of WWP1 enhanced the effect of SHP2 inhibitor in suppressing tumor growth in vitro and in vivo. WWP1 may mediate feedback reactivation of AKT signaling following SHP2 inhibition. Furthermore, nomogram models constructed with IHC expression of WWP1 and SHP2 greatly improved the accuracy of prognosis prediction for patients with CRC. Our findings indicate that WWP1 inhibitor I3C can synergize with SHP2 inhibitor and is expected to be a new strategy for clinical trials in treating advanced CRC patients.

Discovery of Novel Allosteric SHP2 Inhibitor Using Pharmacophore-Based Virtual Screening, Molecular Docking, Molecular Dynamics Simulation, and Principal Component Analysis

SHP2 belongs to a cytoplasmic non-receptor protein tyrosine phosphatase class. It plays a critical role in the development of various cancers, such as gastric cancer, leukemia, and breast cancer. Thus, SHP2 has gained the interest of researchers as a potential target for inhibiting tumor cell proliferation in SHP2-dependent cancers. This study employed pharmacophore-based virtual screening, molecular docking, molecular dynamic (MD) simulations, MM/PBSA, and principal component analysis (PCA), followed by ADME prediction. We selected three potential hits from a collective database of more than one million chemical compounds. The stability of these selected hit-protein complexes was analyzed using 500 ns MD simulations and binding free energy calculations. The identified hits Lig_1, Lig_6, and Lig_14 demonstrated binding free energies of -161.49 kJ/mol, -151.28 kJ/mol, and -107.13 kJ/mol, respectively, compared to the reference molecule (SHP099) with a ΔG of -71.48 kJ/mol. Our results showed that the identified compounds could be used as promising candidates for selective SHP2 allosteric inhibition in cancer.

SHP2 as a primordial epigenetic enzyme expunges histone H3 pTyr-54 to amend androgen receptor homeostasis

Mutations that decrease or increase the activity of the tyrosine phosphatase, SHP2 (encoded by PTPN11), promotes developmental disorders and several malignancies by varying phosphatase activity. We uncovered that SHP2 is a distinct class of an epigenetic enzyme; upon phosphorylation by the kinase ACK1/TNK2, pSHP2 was escorted by androgen receptor (AR) to chromatin, erasing hitherto unidentified pY54-H3 (phosphorylation of histones H3 at Tyr54) epigenetic marks to trigger a transcriptional program of AR. Noonan Syndrome with Multiple Lentigines (NSML) patients, SHP2 knock-in mice, and ACK1 knockout mice presented dramatic increase in pY54-H3, leading to loss of AR transcriptome. In contrast, prostate tumors with high pSHP2 and pACK1 activity exhibited progressive downregulation of pY54-H3 levels and higher AR expression that correlated with disease severity. Overall, pSHP2/pY54-H3 signaling acts as a sentinel of AR homeostasis, explaining not only growth retardation, genital abnormalities and infertility among NSML patients, but also significant AR upregulation in prostate cancer patients.

Targeting KRASG12D mutation in non-small cell lung cancer: molecular mechanisms and therapeutic potential

Lung malignant tumors are a type of cancer with high incidence and mortality rates worldwide. Non-small cell lung cancer (NSCLC) accounts for over 80% of all lung malignant tumors, and most patients are diagnosed at advanced stages, leading to poor prognosis. Over the past decades, various oncogenic driver alterations associated with lung cancer have been identified, each of which can potentially serve as a therapeutic target. Rat sarcoma (RAS) genes are the most commonly mutated oncogenes in human cancers, with Kirsten rat sarcoma (KRAS) being the most common subtype. The role of KRAS oncogene in NSCLC is still not fully understood, and its impact on prognosis remains controversial. Despite the significant advancements in targeted therapy and immune checkpoint inhibitors (ICI) that have transformed the treatment landscape of advanced NSCLC in recent years, targeting KRAS (both directly and indirectly) remains challenging and is still under intensive research. In recent years, significant progress has been made in the development of targeted drugs targeting the NSCLC KRASG12C mutant subtype. However, research progress on target drugs for the more common KRASG12D subtype has been slow, and currently, no specific drugs have been approved for clinical use, and many questions remain to be answered, such as the mechanisms of resistance in this subtype of NSCLC, how to better utilize combination strategies with multiple treatment modalities, and whether KRASG12D inhibitors offer substantial efficacy in the treatment of advanced NSCLC patients.

Off-target autophagy inhibition by SHP2 allosteric inhibitors contributes to their antitumor activity in RAS-driven cancers

Aberrant activation of RAS/MAPK signaling is common in cancer, and efforts to inhibit pathway components have yielded drugs with promising clinical activities. Unfortunately, treatment-provoked adaptive resistance mechanisms inevitably develop, limiting their therapeutic potential. As a central node essential for receptor tyrosine kinase-mediated RAS activation, SHP2 has emerged as an attractive cancer target. Consequently, many SHP2 allosteric inhibitors are now in clinical testing. Here we discovered a previously unrecognized off-target effect associated with SHP2 allosteric inhibitors. We found that these inhibitors accumulate in the lysosome and block autophagic flux in an SHP2-independent manner. We showed that off-target autophagy inhibition by SHP2 allosteric inhibitors contributes to their antitumor activity. We also demonstrated that SHP2 allosteric inhibitors harboring this off-target activity not only suppress oncogenic RAS signaling but also overcome drug resistance such as MAPK rebound and protective autophagy in response to RAS/MAPK pathway blockage. Finally, we exemplified a therapeutic framework that harnesses both the on- and off-target activities of SHP2 allosteric inhibitors for improved treatment of mutant RAS-driven and drug-resistant malignancies such as pancreatic and colorectal cancers.

Targeting SHP2 Cryptic Allosteric Sites for Effective Cancer Therapy

SHP2, a pivotal component downstream of both receptor and non-receptor tyrosine kinases, has been underscored in the progression of various human cancers and neurodevelopmental disorders. Allosteric inhibitors have been proposed to regulate its autoinhibition. However, oncogenic mutations, such as E76K, convert SHP2 into its open state, wherein the catalytic cleft becomes fully exposed to its ligands. This study elucidates the dynamic properties of SHP2 structures across different states, with a focus on the effects of oncogenic mutation on two known binding sites of allosteric inhibitors. Through extensive modeling and simulations, we further identified an alternative allosteric binding pocket in solution structures. Additional analysis provides insights into the dynamics and stability of the potential site. In addition, multi-tier screening was deployed to identify potential binders targeting the potential site. Our efforts to identify a new allosteric site contribute to community-wide initiatives developing therapies using multiple allosteric inhibitors to target distinct pockets on SHP2, in the hope of potentially inhibiting or slowing tumor growth associated with SHP2.

Protein tyrosine phosphatases: emerging role in cancer therapy resistance

BACKGROUND

Tyrosine phosphorylation of intracellular proteins is a post-translational modification that plays a regulatory role in signal transduction during cellular events. Dephosphorylation of signal transduction proteins caused by protein tyrosine phosphatases (PTPs) contributed their role as a convergent node to mediate cross-talk between signaling pathways. In the context of cancer, PTP-mediated pathways have been identified as signaling hubs that enabled cancer cells to mitigate stress induced by clinical therapy. This is achieved by the promotion of constitutive activation of growth-stimulatory signaling pathways or modulation of the immune-suppressive tumor microenvironment. Preclinical evidences suggested that anticancer drugs will release their greatest therapeutic potency when combined with PTP inhibitors, reversing drug resistance that was responsible for clinical failures during cancer therapy.

AREAS COVERED

This review aimed to elaborate recent insights that supported the involvement of PTP-mediated pathways in the development of resistance to targeted therapy and immune-checkpoint therapy.

EXPERT OPINION

This review proposed the notion of PTP inhibition in anticancer combination therapy as a potential strategy in clinic to achieve long-term tumor regression. Ongoing clinical trials are currently underway to assess the safety and efficacy of combination therapy in advanced-stage tumors.

Complex Roles of PTPN11/SHP2 in Carcinogenesis and Prospect of Targeting SHP2 in Cancer Therapy

The non-receptor tyrosine phosphatase SHP2 has been at the center of cell signaling research for three decades. SHP2 is required to fully activate the RTK-RAS-ERK cascade, although the underlying mechanisms are not completely understood. PTPN11, coding for SHP2, is the first identified proto-oncogene that encodes a tyrosine phosphatase, with dominantly activating mutations detected in leukemias and solid tumors. However, SHP2 has been shown to have pro- and anti-oncogenic effects, and the most recent data reveal opposite activities of SHP2 in tumor cells and microenvironment cells. Allosteric SHP2 inhibitors show promising anti-tumor effects and overcome resistance to inhibitors of RAS-ERK signaling in animal models. Many clinical trials with orally bioactive SHP2 inhibitors, alone or combined with other regimens, are ongoing for a variety of cancers worldwide, with therapeutic outcomes yet unknown. This review discusses the multi-faceted SHP2 functions in oncogenesis, preclinical studies and clinical trials with SHP2 inhibitors in oncological treatment.

Tumor biomarkers for diagnosis, prognosis and targeted therapy

Tumor biomarkers, the substances which are produced by tumors or the body's responses to tumors during tumorigenesis and progression, have been demonstrated to possess critical and encouraging value in screening and early diagnosis, prognosis prediction, recurrence detection, and therapeutic efficacy monitoring of cancers. Over the past decades, continuous progress has been made in exploring and discovering novel, sensitive, specific, and accurate tumor biomarkers, which has significantly promoted personalized medicine and improved the outcomes of cancer patients, especially advances in molecular biology technologies developed for the detection of tumor biomarkers. Herein, we summarize the discovery and development of tumor biomarkers, including the history of tumor biomarkers, the conventional and innovative technologies used for biomarker discovery and detection, the classification of tumor biomarkers based on tissue origins, and the application of tumor biomarkers in clinical cancer management. In particular, we highlight the recent advancements in biomarker-based anticancer-targeted therapies which are emerging as breakthroughs and promising cancer therapeutic strategies. We also discuss limitations and challenges that need to be addressed and provide insights and perspectives to turn challenges into opportunities in this field. Collectively, the discovery and application of multiple tumor biomarkers emphasized in this review may provide guidance on improved precision medicine, broaden horizons in future research directions, and expedite the clinical classification of cancer patients according to their molecular biomarkers rather than organs of origin.

Combinatorial strategies to target RAS-driven cancers

Although RAS was formerly considered undruggable, various agents that inhibit RAS or specific RAS oncoproteins have now been developed. Indeed, the importance of directly targeting RAS has recently been illustrated by the clinical success of mutant-selective KRAS inhibitors. Nevertheless, responses to these agents are typically incomplete and restricted to a subset of patients, highlighting the need to develop more effective treatments, which will likely require a combinatorial approach. Vertical strategies that target multiple nodes within the RAS pathway to achieve deeper suppression are being investigated and have precedence in other contexts. However, alternative strategies that co-target RAS and other therapeutic vulnerabilities have been identified, which may mitigate the requirement for profound pathway suppression. Regardless, the efficacy of any given approach will likely be dictated by genetic, epigenetic and tumour-specific variables. Here we discuss various combinatorial strategies to treat KRAS-driven cancers, highlighting mechanistic concepts that may extend to tumours harbouring other RAS mutations. Although many promising combinations have been identified, clinical responses will ultimately depend on whether a therapeutic window can be achieved and our ability to prospectively select responsive patients. Therefore, we must continue to develop and understand biologically diverse strategies to maximize our likelihood of success.

From bench to bedside: current development and emerging trend of KRAS-targeted therapy

Kirsten rat sarcoma 2 viral oncogene homolog (KRAS) is the most frequently mutated oncogene in human cancers with mutations predominantly occurring in codon 12. These mutations disrupt the normal function of KRAS by interfering with GTP hydrolysis and nucleotide exchange activity, making it prone to the GTP-bound active state, thus leading to sustained activation of downstream pathways. Despite decades of research, there has been no progress in the KRAS drug discovery until the groundbreaking discovery of covalently targeting the KRASG12C mutation in 2013, which led to revolutionary changes in KRAS-targeted therapy. So far, two small molecule inhibitors sotorasib and adagrasib targeting KRASG12C have received accelerated approval for the treatment of non-small cell lung cancer (NSCLC) harboring KRASG12C mutations. In recent years, rapid progress has been achieved in the KRAS-targeted therapy field, especially the exploration of KRASG12C covalent inhibitors in other KRASG12C-positive malignancies, novel KRAS inhibitors beyond KRASG12C mutation or pan-KRAS inhibitors, and approaches to indirectly targeting KRAS. In this review, we provide a comprehensive overview of the molecular and mutational characteristics of KRAS and summarize the development and current status of covalent inhibitors targeting the KRASG12C mutation. We also discuss emerging promising KRAS-targeted therapeutic strategies, with a focus on mutation-specific and direct pan-KRAS inhibitors and indirect KRAS inhibitors through targeting the RAS activation-associated proteins Src homology-2 domain-containing phosphatase 2 (SHP2) and son of sevenless homolog 1 (SOS1), and shed light on current challenges and opportunities for drug discovery in this field.

Fragment-Based Discovery of Allosteric Inhibitors of SH2 Domain-Containing Protein Tyrosine Phosphatase-2 (SHP2)

The ubiquitously expressed protein tyrosine phosphatase SHP2 is required for signaling downstream of receptor tyrosine kinases (RTKs) and plays a role in regulating many cellular processes. Genetic knockdown and pharmacological inhibition of SHP2 suppresses RAS/MAPK signaling and inhibit the proliferation of RTK-driven cancer cell lines. Here, we describe the first reported fragment-to-lead campaign against SHP2, where X-ray crystallography and biophysical techniques were used to identify fragments binding to multiple sites on SHP2. Structure-guided optimization, including several computational methods, led to the discovery of two structurally distinct series of SHP2 inhibitors binding to the previously reported allosteric tunnel binding site (Tunnel Site). One of these series was advanced to a low-nanomolar lead that inhibited tumor growth when dosed orally to mice bearing HCC827 xenografts. Furthermore, a third series of SHP2 inhibitors was discovered binding to a previously unreported site, lying at the interface of the C-terminal SH2 and catalytic domains.

Tyrosine phosphatase PTPN11/SHP2 in solid tumors - bull's eye for targeted therapy?

Encoded by PTPN11, the Src-homology 2 domain-containing phosphatase 2 (SHP2) integrates signals from various membrane-bound receptors such as receptor tyrosine kinases (RTKs), cytokine and integrin receptors and thereby promotes cell survival and proliferation. Activating mutations in the PTPN11 gene may trigger signaling pathways leading to the development of hematological malignancies, but are rarely found in solid tumors. Yet, aberrant SHP2 expression or activation has implications in the development, progression and metastasis of many solid tumor entities. SHP2 is involved in multiple signaling cascades, including the RAS-RAF-MEK-ERK-, PI3K-AKT-, JAK-STAT- and PD-L1/PD-1- pathways. Although not mutated, activation or functional requirement of SHP2 appears to play a relevant and context-dependent dichotomous role. This mostly tumor-promoting and infrequently tumor-suppressive role exists in many cancers such as gastrointestinal tumors, pancreatic, liver and lung cancer, gynecological entities, head and neck cancers, prostate cancer, glioblastoma and melanoma. Recent studies have identified SHP2 as a potential biomarker for the prognosis of some solid tumors. Based on promising preclinical work and the advent of orally available allosteric SHP2-inhibitors early clinical trials are currently investigating SHP2-directed approaches in various solid tumors, either as a single agent or in combination regimes. We here provide a brief overview of the molecular functions of SHP2 and collate current knowledge with regard to the significance of SHP2 expression and function in different solid tumor entities, including cells in their microenvironment, immune escape and therapy resistance. In the context of the present landscape of clinical trials with allosteric SHP2-inhibitors we discuss the multitude of opportunities but also limitations of a strategy targeting this non-receptor protein tyrosine phosphatase for treatment of solid tumors.

Progress in RAS-targeted therapeutic strategies: From small molecule inhibitors to proteolysis targeting chimeras

As a widely considerable target in chemical biology and pharmacological research, rat sarcoma (RAS) gene mutations play a critical driving factor in several fatal cancers. Despite the great progress of RAS subtype-specific inhibitors, rapid acquired drug resistance could limit their further clinical applications. Proteolysis targeting chimera (PROTAC) has emerged as a powerful tool to handle "undruggable" targets and exhibited significant therapeutic benefit for the combat of drug resistance. Owing to unique molecular mechanism and binding kinetics, PROTAC is expected to become a feasible strategy to break the bottleneck of classical RAS inhibitors. This review aims to discuss the current advances of RAS inhibitors and especially focus on PROTAC strategy targeting RAS mutations and their downstream effectors for relevant cancer treatment.

Targeting KRAS and SHP2 signaling pathways for immunomodulation and improving treatment outcomes in solid tumors

Historically, KRAS has been considered 'undruggable' inspite of being one of the most frequently altered oncogenic proteins in solid tumors, primarily due to the paucity of pharmacologically 'druggable' pockets within the mutant isoforms. However, pioneering developments in drug design capable of targeting the mutant KRAS isoforms especially KRASG12C-mutant cancers, have opened the doors for emergence of combination therapies comprising of a plethora of inhibitors targeting different signaling pathways. SHP2 signaling pathway, primarily known for activation of intracellular signaling pathways such as KRAS has come up as a potential target for such combination therapies as it emerged to be the signaling protein connecting KRAS and the immune signaling pathways and providing the link for understanding the overlapping regions of RAS/ERK/MAPK signaling cascade. Thus, SHP2 inhibitors having potent tumoricidal activity as well as role in immunomodulation have generated keen interest in researchers to explore its potential as combination therapy in KRAS mutant solid tumors. However, the excitement with these combination therapies need to overcome challenges thrown up by drug resistance and enhanced toxicity. In this review, we will discuss KRAS and SHP2 signaling pathways and their roles in immunomodulation and regulation of tumor microenvironment and also analyze the positive effects and drawbacks of the different combination therapies targeted at these signaling pathways along with their present and future potential to treat solid tumors.

Re-expression of epigenetically silenced PTPRR by histone acetylation sensitizes RAS-mutant lung adenocarcinoma to SHP2 inhibition

Silenced protein tyrosine phosphatase receptor type R (PTPRR) participates in mitogen-activated protein kinase (MAPK) signaling cascades during the genesis and development of tumors. Rat sarcoma virus (Ras) genes are frequently mutated in lung adenocarcinoma, thereby resulting in hyperactivation of downstream MAPK signaling. However, the molecular mechanism manipulating the regulation and function of PTPRR in RAS-mutant lung adenocarcinoma is not known. Patient records collected from the Cancer Genome Atlas and Gene Expression Omnibus showed that silenced PTPRR was positively correlated with the prognosis. Exogenous expression of PTPRR suppressed the proliferation and migration of lung cancer cells. PTPRR expression and Src homology 2 containing protein tyrosine phosphatase 2 (SHP2) inhibition acted synergistically to control ERK1/2 phosphorylation in RAS-driven lung cancer cells. Chromatin immunoprecipitation assay revealed that HDAC inhibition induced enriched histone acetylation in the promoter region of PTPRR and recovered PTPRR transcription. The combination of the HDAC inhibitor SAHA and SHP2 inhibitor SHP099 suppressed the progression of lung cancer markedly in vitro and in vivo. Therefore, we revealed the epigenetic silencing mechanism of PTPRR and demonstrated that combination therapy targeting HDAC and SHP2 might represent a novel strategy to treat RAS-mutant lung cancer.

Inhibition of the RAF/MEK/ERK Signaling Cascade in Pancreatic Cancer: Recent Advances and Future Perspectives

Pancreatic cancer represents a formidable challenge in oncology, primarily due to its aggressive nature and limited therapeutic options. The prognosis of patients with pancreatic ductal adenocarcinoma (PDAC), the main form of pancreatic cancer, remains disappointingly poor with a 5-year overall survival of only 5%. Almost 95% of PDAC patients harbor Kirsten rat sarcoma virus (KRAS) oncogenic mutations. KRAS activates downstream intracellular pathways, most notably the rapidly accelerated fibrosarcoma (RAF)/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling axis. Dysregulation of the RAF/MEK/ERK pathway is a crucial feature of pancreatic cancer and therefore its main components, RAF, MEK and ERK kinases, have been targeted pharmacologically, largely by small-molecule inhibitors. The recent advances in the development of inhibitors not only directly targeting the RAF/MEK/ERK pathway but also indirectly through inhibition of its regulators, such as Src homology-containing protein tyrosine phosphatase 2 (SHP2) and Son of sevenless homolog 1 (SOS1), provide new therapeutic opportunities. Moreover, the discovery of allele-specific small-molecule inhibitors against mutant KRAS variants has brought excitement for successful innovations in the battle against pancreatic cancer. Herein, we review the recent advances in targeted therapy and combinatorial strategies with focus on the current preclinical and clinical approaches, providing critical insight, underscoring the potential of these efforts and supporting their promise to improve the lives of patients with PDAC.

Targeting cancer stem cell OXPHOS with tailored ruthenium complexes as a new anti-cancer strategy

BACKGROUND

Previous studies by our group have shown that oxidative phosphorylation (OXPHOS) is the main pathway by which pancreatic cancer stem cells (CSCs) meet their energetic requirements; therefore, OXPHOS represents an Achille's heel of these highly tumorigenic cells. Unfortunately, therapies that target OXPHOS in CSCs are lacking.

METHODS

The safety and anti-CSC activity of a ruthenium complex featuring bipyridine and terpyridine ligands and one coordination labile position (Ru1) were evaluated across primary pancreatic cancer cultures and in vivo, using 8 patient-derived xenografts (PDXs). RNAseq analysis followed by mitochondria-specific molecular assays were used to determine the mechanism of action.

RESULTS

We show that Ru1 is capable of inhibiting CSC OXPHOS function in vitro, and more importantly, it presents excellent anti-cancer activity, with low toxicity, across a large panel of human pancreatic PDXs, as well as in colorectal cancer and osteosarcoma PDXs. Mechanistic studies suggest that this activity stems from Ru1 binding to the D-loop region of the mitochondrial DNA of CSCs, inhibiting OXPHOS complex-associated transcription, leading to reduced mitochondrial oxygen consumption, membrane potential, and ATP production, all of which are necessary for CSCs, which heavily depend on mitochondrial respiration.

CONCLUSIONS

Overall, the coordination complex Ru1 represents not only an exciting new anti-cancer agent, but also a molecular tool to dissect the role of OXPHOS in CSCs. Results indicating that the compound is safe, non-toxic and highly effective in vivo are extremely exciting, and have allowed us to uncover unprecedented mechanistic possibilities to fight different cancer types based on targeting CSC OXPHOS.

Targeting Protein Tyrosine Phosphatases to Improve Cancer Immunotherapies

Advances in immunotherapy have brought significant therapeutic benefits to many cancer patients. Nonetheless, many cancer types are refractory to current immunotherapeutic approaches, meaning that further targets are required to increase the number of patients who benefit from these technologies. Protein tyrosine phosphatases (PTPs) have long been recognised to play a vital role in the regulation of cancer cell biology and the immune response. In this review, we summarize the evidence for both the pro-tumorigenic and tumour-suppressor function of non-receptor PTPs in cancer cells and discuss recent data showing that several of these enzymes act as intracellular immune checkpoints that suppress effective tumour immunity. We highlight new data showing that the deletion of inhibitory PTPs is a rational approach to improve the outcomes of adoptive T cell-based cancer immunotherapies and describe recent progress in the development of PTP inhibitors as anti-cancer drugs.

Direct K-Ras Inhibitors to Treat Cancers: Progress, New Insights, and Approaches to Treat Resistance

Here we discuss approaches to K-Ras inhibition and drug resistance scenarios. A breakthrough offered a covalent drug against K-RasG12C. Subsequent innovations harnessed same-allele drug combinations, as well as cotargeting K-RasG12C with a companion drug to upstream regulators or downstream kinases. However, primary, adaptive, and acquired resistance inevitably emerge. The preexisting mutation load can explain how even exceedingly rare mutations with unobservable effects can promote drug resistance, seeding growth of insensitive cell clones, and proliferation. Statistics confirm the expectation that most resistance-related mutations are in cis, pointing to the high probability of cooperative, same-allele effects. In addition to targeted Ras inhibitors and drug combinations, bifunctional molecules and innovative tri-complex inhibitors to target Ras mutants are also under development. Since the identities and potential contributions of preexisting and evolving mutations are unknown, selecting a pharmacologic combination is taxing. Collectively, our broad review outlines considerations and provides new insights into pharmacology and resistance.

Pancreatic cancer acquires resistance to MAPK pathway inhibition by clonal expansion and adaptive DNA hypermethylation

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with poor prognosis. It is marked by extraordinary resistance to conventional therapies including chemotherapy and radiation, as well as to essentially all targeted therapies evaluated so far. More than 90% of PDAC cases harbor an activating KRAS mutation. As the most common KRAS variants in PDAC remain undruggable so far, it seemed promising to inhibit a downstream target in the MAPK pathway such as MEK1/2, but up to now preclinical and clinical evaluation of MEK inhibitors (MEKi) failed due to inherent and acquired resistance mechanisms. To gain insights into molecular changes during the formation of resistance to oncogenic MAPK pathway inhibition, we utilized short-term passaged primary tumor cells from ten PDACs of genetically engineered mice. We followed gain and loss of resistance upon MEKi exposure and withdrawal by longitudinal integrative analysis of whole genome sequencing, whole genome bisulfite sequencing, RNA-sequencing and mass spectrometry data.

RESULTS

We found that resistant cell populations under increasing MEKi treatment evolved by the expansion of a single clone but were not a direct consequence of known resistance-conferring mutations. Rather, resistant cells showed adaptive DNA hypermethylation of 209 and hypomethylation of 8 genomic sites, most of which overlap with regulatory elements known to be active in murine PDAC cells. Both DNA methylation changes and MEKi resistance were transient and reversible upon drug withdrawal. Furthermore, MEKi resistance could be reversed by DNA methyltransferase inhibition with remarkable sensitivity exclusively in the resistant cells.

CONCLUSION

Overall, the concept of acquired therapy resistance as a result of the expansion of a single cell clone with epigenetic plasticity sheds light on genetic, epigenetic and phenotypic patterns during evolvement of treatment resistance in a tumor with high adaptive capabilities and provides potential for reversion through epigenetic targeting.

Drugging the undruggable: Advances in targeting KRAS signaling in solid tumors

Cancer remains the leading cause of global mortality, prompting a paradigm shift in its treatment and outcomes with the advent of targeted therapies. Among the most prevalent mutations in RAS-driven cancers, Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations account for approximately 86% of cases worldwide, particularly in lung, pancreatic, and colon cancers, contributing to poor prognosis and reduced overall survival. Despite numerous efforts to understand the biology of KRAS mutants and their pivotal role in cancer development, the lack of well-defined drug-binding pockets has deemed KRAS an "undruggable" therapeutic target, presenting significant challenges for researchers and clinicians alike. Through significant biochemical and technological advances, the last decade has witnessed promising breakthroughs in targeted therapies for KRAS-mutated lung, colon, and pancreatic cancers, marking a critical turning point in the field. In this chapter, we provide an overview of the characteristics of KRAS mutations across various solid tumors, highlighting ongoing cutting-edge research on the immune microenvironment, the development of KRAS-driven mice models, and the recent progress in the exploration of specific KRAS mutant-targeted therapeutic approaches. By comprehensive understanding of the intricacies of KRAS signaling in solid tumors and the latest therapeutic developments, this chapter will shed light on the potential for novel therapeutic strategies to combat KRAS-driven tumors and improve patient outcomes.

Progesterone and cAMP synergistically induce SHP2 expression via PGR and CREB1 during uterine stromal decidualization

Decidualization of endometrial stroma is a key step in embryo implantation and its abnormality often leads to pregnancy failure. Stromal decidualization is a very complex process that is co-regulated by estrogen, progesterone and many local factors. The signaling protein SHP2 encoded by PTPN11 is dynamically expressed in decidualized endometrial stroma and mediates and integrates various signals to govern the decidualization. In the present study, we investigate the mechanism of PTPN11 gene transcription. Estrogen, progesterone and cAMP co-induced decidualization of human endometrial stromal cell in vitro, but only progesterone and cAMP induced SHP2 expression. Using the luciferase reporter, we refined a region from -229 bp to +1 bp in the PTPN11 gene promoter comprising the transcriptional core regions that respond to progesterone and cAMP. Progesterone receptor (PGR) and cAMP-responsive element-binding protein 1 (CREB1) were predicted to be transcription factors in this core region by bioinformatic methods. The direct binding of PGR and CREB1 on the PTPN11 promoter was confirmed by electrophoretic mobility and chromatin immunoprecipitation in vitro. Knockdown of PGR and CREB1 protein significantly inhibited the expression of SHP2 induced by medroxyprogesterone acetate and cAMP. These results demonstrate that transcription factors PGR and CREB1 bind to the PTPN11 promoter to regulate the expression of SHP2 in response to decidual signals. Our results explain the transcriptional expression mechanism of SHP2 during decidualization and promote the understanding of the mechanism of decidualization of stromal cells.

Advances and challenges in the treatment of lung cancer

Lung cancer accounts for a relatively high proportion of malignant tumors. As the most prevalent type of lung cancer, non-small cell lung cancer (NSCLC) is characterized by high morbidity and mortality. Presently, the arsenal of treatment strategies encompasses surgical resection, chemotherapy, targeted therapy and radiotherapy. However, despite these options, the prognosis remains distressingly poor with a low 5-year survival rate. Therefore, it is urgent to pursue a paradigm shift in treatment methodologies. In recent years, the advent of sophisticated biotechnologies and interdisciplinary integration has provided innovative approaches for the treatment of lung cancer. This article reviews the cutting-edge developments in the nano drug delivery system, molecular targeted treatment system, photothermal treatment strategy, and immunotherapy for lung cancer. Overall, by systematically summarizing and critically analyzing the latest progress and current challenges in these treatment strategies of lung cancer, we aim to provide a theoretical basis for the development of novel drugs for lung cancer treatment, and thus improve the therapeutic outcomes for lung cancer patients.