A phase II trial of Salirasib in patients with lung adenocarcinomas with KRAS mutations

KRAS mutations in colorectal cancer: impacts on tumor microenvironment and therapeutic implications

INTRODUCTION

Despite decreasing trends in incidence, colorectal cancer (CRC) is still a major contributor to malignancy-related morbidities and mortalities. Groundbreaking advances in immunotherapies and targeted therapies benefit a subset of CRC patients, with sub-optimal outcomes. Hence, there is an unmet need to design and manufacture novel therapies, especially for advanced/metastatic disease. KRAS, the most highly mutated proto-oncogene across human malignancies, particularly in pancreatic adenocarcinoma, non-small cell lung cancer, and CRC, is an on-off switch and governs several fundamental cell signaling cascades. KRAS mutations not only propel the progression and metastasis of CRC but also critically modulate responses to targeted therapies.

AREAS COVERED

We discuss the impacts of KRAS mutations on the CRC's tumor microenvironment and describe novel strategies for targeting KRAS and its associated signaling cascades and mechanisms of drug resistance.

EXPERT OPINION

Drug development against KRAS mutations has been challenging, mainly due to structural properties (offering no appropriate binding site for small molecules), critical functions of the wild-type KRAS in non-cancerous cells, and the complex network of its downstream effector pathways (allowing malignant cells to develop resistance). Pre-clinical and early clinical data offer promises for combining KRAS inhibitors with immunotherapies and targeted therapies.

Phosphorylation of POU3F3 Mediated Nuclear Translocation Promotes Proliferation in Non-Small Cell Lung Cancer through Accelerating ATP5PF Transcription and ATP Production

Targeting oxidative phosphorylation (OXPHOS) through inhibiting the electron transport chain (ETC) has shown promising pre-clinical efficacy in cancer therapy. Although aerobic glycolysis is a hallmark of cancer, emerging evidence suggest OXPHOS is frequently enhanced, providing metabolic advantages for cell proliferation, metastasis, and drug resistance in a variety of aggressive cancer types including non-small cell lung cancer (NSCLC), yet the underlying molecular mechanisms remain elusive. Here it is reported that POU-domain containing family protein POU3F3 is translocated into the nuclei of NSCLC cell lines harboring mutant RAS, where it activates transcription of ATP5PF, an essential component of mitochondrial ATP synthase and consequent ATP production, leading to enhanced NSCLC proliferation and migration. Moreover, it is further found out that ERK1 phosphorylates POU3F3 at the S393 site in the cytoplasm and promotes the nuclear translocation of POU3F3 via receptor importin β1 in RAS mutant NSCLC cells. Mechanistically, RNA sequencing analysis combined with chromatin immunoprecipitation (ChIP) assay revealed that POU3F3 binds to the promoter of ATP5PF, leading to enhanced ATP5PF transcription and ATP production. Together, this study uncovers a novel RAS-POU3F3-ATP5PF axis in facilitating NSCLC progression, providing a new perspective on the understanding of molecular mechanisms for NSCLC progression.

Structural insights, regulation, and recent advances of RAS inhibitors in the MAPK signaling cascade: a medicinal chemistry perspective

The MAPK pathway has four main components: RAS, RAF, MEK, and ERK. Among these, RAS is the most frequently mutated protein and the leading cause of cancer. The three isoforms of the RAS gene are HRAS, NRAS, and KRAS. The KRAS gene is characterized by two splice variants, K-Ras4A and K-Ras4B. The occurrence of cancer often involves a mutation in both KRAS4A and KRAS4B. In this study, we have elucidated the mechanism of the RAS protein complex and the movement of switches I and II. Only two RAS inhibitors, sotorasib and adagrasib, have been approved by the FDA, and several are in clinical trials. This review comprises recent developments in synthetic RAS inhibitors, their unique properties, their importance in inhibiting RAS mutations, and the current challenges in developing new RAS inhibitors. This review will undoubtedly help researchers design novel RAS inhibitors.

The continually evolving landscape of novel therapies in oncogene-driven advanced non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) is a highly heterogeneous disease that is frequently associated with a host of known oncogenic alterations. Advances in molecular diagnostics and drug development have facilitated the targeting of novel alterations such that the majority of NSCLC patients have driver mutations that are now clinically actionable. The goal of this review is to gain insights into clinical research and development principles by summary, analysis, and discussion of data on agents targeting known alterations in oncogene-driven, advanced NSCLC beyond those in the epidermal growth factor receptor (EGFR) and the anaplastic lymphoma kinase (ALK). A search of published and presented literature was conducted to identify prospective trials and integrated analyses reporting outcomes for agents targeting driver gene alterations (except those in EGFR and ALK) in molecularly selected, advanced NSCLC. Clinical efficacy data were extracted from eligible reports and summarized in text and tables. Findings show that research into alteration-directed therapies in oncogene-driven, advanced NSCLC is an extremely active research field. Ongoing research focuses on the expansion of new agents targeting both previously identified targets (particularly hepatocyte growth factor receptor (MET), human epidermal growth factor receptor 2 (HER2), and Kirsten rat sarcoma viral oncogene homolog (KRAS)) as well as novel, potentially actionable targets (such as neuregulin-1 (NRG1) and phosphatidylinositol 3-kinase (PI3K)). The refinement of biomarker selection criteria and the development of more selective and potent agents are allowing for increasingly specific and effective therapies and the expansion of clinically actionable alterations. Clinical advances in this field have resulted in a large number of regulatory approvals over the last 3 years. Future developments should focus on the continued application of alteration therapy matching principles and the exploration of novel ways to target oncogene-driven NSCLC.

Synergistic two-step inhibition approach using a combination of trametinib and onvansertib in KRAS and TP53-mutated colorectal adenocarcinoma

Colorectal malignancies associated with KRAS and TP53 mutations led us to investigate the effects of combination therapy targeting KRAS, MEK1, or PLK1 in colorectal cancer. MEK1 is downstream of RAS in the MAPK pathway, whereas PLK1 is a mitotic kinase of the cell cycle activated by MAPK and regulated by p53. Bioinformatics analysis revealed that patients with colorectal cancer had a high expression of MAP2K1 and PLK1. Furthermore, PLK1 and MEK1 activity in human colorectal adenocarcinoma (COAD) tissues was found to be highly upregulated compared to healthy tissues. To determine the sensitivity of KRAS or/and TP53-mutated cancer to KRAS, MEK1, or PLK1-targeted therapy, the inhibitors salirasib, trametinib, volasertib, and onvansertib were used in COAD cells with different KRAS and TP53 status. The results showed that combinations with trametinib and PLK1 inhibitors were more potent than combinations with salirasib. A combination of MEK1 and PLK1 inhibitors exhibited significant therapeutic effects on KRAS or/and TP53-mutated COAD cells. Notably, the combination of trametinib and onvansertib effectively suppressed tumor growth in a xenograft mouse model of KRAS and TP53-mutated COAD. This treatment induced G1 and G2/M arrest, respectively, and showed the strongest synergistic effect in KRAS and TP53-mutated SW48 cells expressing mutant KRASG13D and transduced with TP53 shRNA, ultimately leading to apoptotic cell death. These effects are attributed to two-step inhibition mechanism that blocks the MAPK signaling pathway and disrupts mitosis in KRAS and TP53-mutated COAD cells.

Decoding KRAS mutation in non-small cell lung cancer patients receiving immunotherapy: A retrospective institutional comparison and literature review

INTRODUCTION

KRAS mutation the most common molecular alteration in advanced non-small cell lung cancer (NSCLC) and is associated with an unfavourable prognosis, largely due to the lack of targeted therapeutic options for the majority of the KRAS mutated isoforms. The landscape of NSCLC treatment has expanded with the introduction of immune checkpoint inhibitors (ICIs). Nonetheless, data regarding the efficacy of ICI in NSCLC patients harbouring KRAS mutations are conflicting. This study aimed to compare clinical outcomes of ICIs in advanced NSCLC with different isoforms of KRAS mutations.

METHODS

A retrospective study was conducted on 143 patients with advanced NSCLC harbouring different KRAS mutation and treated with immune checkpoint inhibitors (ICI) between December 2020 and July 2022 at "Fondazione IRCCS Istituto Nazionale dei Tumori" in Milan. Log-rank and Cox Hazard methods were used for survival analysis.

RESULTS

We evaluated 143 patients with advanced non-small cell lung cancer (NSCLC) harboring KRAS mutations. The most common mutation was G12C (41 %), followed by G12V (23.7 %) and G12D (11.8 %). The G12C mutation was notably associated with a higher incidence of bone metastases (42 %). Immunotherapy was administered as monotherapy in 54.5 % of cases, while 69 % received it as part of a first-line combination with chemotherapy. Co-mutations were detected in 52 % of patients, with Q61 (63 %) and G12C (58 %) being the most prevalent. Among these, 24 % had STK11 co-mutations, and 29 % had TP53 co-mutations. No significant differences in overall survival (OS) or progression-free survival (PFS) were observed across different KRAS subtypes. The longest OS was seen in patients with Q61 (46.5 months), 13X (31.8 months), and G12C (28.7 months). The highest overall response rate (ORR) of 73 % was observed in the G12D group, particularly with the combination of chemoimmunotherapy, where stable disease was the most common outcome at 40 %. The median duration of response (DOR) was 7.4 months across both treatments. The longest DOR was seen in the G12V group at 10.2 months, with no significant difference between treatments. In contrast, the shortest DOR was in the G12A group, with 1.54 months in those treated with combination therapy compared to 2.57 months with single-agent therapy. Regarding co-mutations, patients with STK11 co-mutations had a higher median OS than those without (39.7 vs. 26.1 months), but this was not statistically significant (p = 1). Similarly, TP53 co-mutations were associated with a lower median OS (19.1 vs. 26.1 months, p = 0.7), though this too was not statistically significant. Importantly, bone metastases emerged as a significant adverse prognostic factor, nearly doubling the risk of mortality (HR: 2.81, p < 0.001), regardless of KRAS subtype or co-mutation status.

CONCLUSION

KRAS mutation subtypes demonstrate varying clinical outcomes. Although no statistically significant differences were observed in overall survival (OS) or progression-free survival (PFS), bone metastases were identified as a significant adverse prognostic factor, nearly doubling the risk of mortality (HR: 2.72, p < 0.001) regardless of KRAS subtype or co-mutation status. These findings underscore the importance of personalized treatment approaches tailored to the genetic profiles of patients with advanced NSCLC.

Clinical Advances and Challenges in Targeting KRAS Mutations in Non-Small Cell Lung Cancer

KRAS mutation is one of the most common oncogenic drivers in non-small cell lung cancer. Since its discovery about four decades ago, drug development targeting KRAS has been met with countless failures. Recently, KRAS G12C, a subvariant of KRAS, became the first druggable KRAS mutation. The efficacy of the first-generation KRAS inhibitor is modest, but with scientific advancement, KRAS G12C inhibitors with higher potency are on the horizon. Additionally, novel therapeutic approaches targeting other KRAS subvariants are also being explored in clinical trials with encouraging early data. We will review the clinical advances and challenges for patients with KRAS-mutated non-small cell lung cancer, with a focus on small molecule inhibitors.

Duodenal Fluid Analysis as a Rewarding Approach to Detect Low-Abundance Mutations in Biliopancreatic Cancers

Diagnosis of biliopancreatic cancers by the available serum tumor markers, imaging, and histopathological tissue specimen examination remains a challenge. Circulating cell-free DNA derived from matched pairs of secretin-stimulated duodenal fluid (DF) and plasma from 10 patients with biliopancreatic diseases and 8 control subjects was analyzed using AmpliSeq™ HD technology for Ion Torrent Next-Generation Sequencing to evaluate the potential of liquid biopsy with DF in biliopancreatic cancers. The median cfDNA concentration was greater in DF-derived than in plasma-derived samples. A total of 13 variants were detected: 11 vs. 1 were exclusive for DF relative to the plasma source, and 1 was shared between the two body fluids. According to the four-tier systems, 10 clinical tier-I-II (76.9%), 1 tier-III (7.7%), and 2 tier-IV (15.4%) variants were identified. Notably, the 11 tier-I-III variants were exclusively found in DF-derived cfDNA from five patients with biliopancreatic cancers, and were detected in seven genes (KRAS, TP53, BRAF, CDKN2A, RNF43, GNAS, and PIK3CA); 82% of the tier-I-III variants had a low abundance, with a VAF < 6%. The mutational profiling of DF seems to be a reliable and promising tool for identifying cancer-associated alterations in malignant cancers of the biliopancreatic tract.

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.

Targeting KRASG12C in Non-Small-Cell Lung Cancer: Current Standards and Developments

Among the most common molecular alterations detected in non-small-cell lung cancer (NSCLC) are mutations in Kristen Rat Sarcoma viral oncogene homolog (KRAS). KRAS mutant NSCLC is a heterogenous group of diseases, different from other oncogene-driven tumors in terms of biology and response to therapies. Despite efforts to develop drugs aimed at inhibiting KRAS or its signaling pathways, KRAS had remained undruggable for decades. The discovery of a small pocket in the binding switch II region of KRASG12C has revolutionized the treatment of KRASG12C-mutated NSCLC patients. Sotorasib and adagrasib, direct KRASG12C inhibitors, have been approved by the US Food and Drug Administration (FDA) and other regulatory agencies for patients with previously treated KRASG12C-mutated NSCLC, and these advances have become practice changing. However, first-line treatment in KRASG12C-mutated NSCLC does not differ from NSCLC without actionable driver genomic alterations. Treatment with KRASG12C inhibitors is not curative and patients develop progressive disease, so understanding associated mechanisms of drug resistance is key. New KRASG12C inhibitors and several combination therapy strategies, including with immune checkpoint inhibitors, are being studied in clinical trials. The aim of this review is to explore the clinical impact of KRAS, and outline different treatment approaches, focusing on the novel treatment of KRASG12C-mutated NSCLC.

Recent Advances in Therapeutic Strategies to Improve Colorectal Cancer Treatment

Colorectal cancer (CRC) is the second-leading cause of cancer-related mortality worldwide. CRC mortality results almost exclusively from metastatic disease (mCRC) for which systemic chemotherapy is often a preferred therapeutic option. Biomarker-based stratification of mCRC enables the use of precision therapy based on individual tumor mutational profiles. Activating mutations in the RAS/RAF/MAPK pathway downstream of EGFR signaling have, until recently, limited the use of EGFR-targeted therapies for mCRC; however, the development of anti-RAS and anti-RAF therapies together with improved strategies to limit compensatory signaling pathways is resulting in improved survival rates in several highly lethal mCRC sub-types (e.g., BRAF-mutant). The use of fluoropyrimidine (FP)-based chemotherapy regimens to treat mCRC continues to evolve contributing to improved long-term survival. Future advances in chemotherapy for mCRC will need to position development relative to the advances made in precision oncology.

Deciphering the role of KRAS gene in oncogenesis: Focus on signaling pathways, genetic alterations in 3'UTR, KRAS specific miRNAs and therapeutic interventions

Cancer is a significant cause of death after cardiovascular disease. The genomic, epigenetic and environmental factors have been found to be the risk factor for the disease. The most important genes that develop cancer are oncogenes and tumor suppressor genes. Among oncogenes, KRAS has emerged as a significant player in the development of many cancers. Dysregulation of the RAS signaling pathway either on account of mutation in significant genes involved in the pathway or aberrant expression of different miRNAs targeting these genes including KRAS. The focus is also on the alterations in 3'UTR of the KRAS gene sequence as well as the changes in the miRNA encoding genes especially the one targeting the KRAS gene. Efforts are also being put in to target the dysregulated KRAS gene as a therapeutic approach to treat different cancers. However, there are some challenges like resistance to KRAS inhibitors that need to be addressed.

Lipophilic modification of salirasib modulates the antiproliferative and antimigratory activity

Salirasib, or farnesylthiosalicylic acid (FTS), is a salicylic acid derivative with demonstrated antineoplastic activity. While designed as a competitor of the substrate S-farnesyl cysteine on Ras, it is a potent competitive inhibitor of isoprenylcysteine carboxymethyl transferase. In this study, the antiproliferative activity on six different solid tumor cell lines was evaluated with a series of lipophilic thioether modified salirasib analogues, including those with or without a 1,2,3-triazole linker. A combination of bioassay, cheminformatics, docking, and in silico ADME-Tox was also performed. SAR analysis that analogues with three or more isoprene units or a long aliphatic chain exhibited the most potent activity. Furthermore, three compounds display superior antiproliferative activity than salirasib and similar potency compared to control anticancer drugs across all tested solid tumor cell lines. In addition, the behavior of the collection on migration and invasion, a key process in tumor metastasis, was also studied. Three analogues with specific antimigratory activity were identified with differential structural features being interesting starting points on the development of new antimetastatic agents. The antiproliferative and antimigratory effects observed suggest that modifying the thiol aliphatic/prenyl substituents can modulate the activity.

RAS signaling and immune cells: a sinister crosstalk in the tumor microenvironment

The rat sarcoma virus (RAS) gene is the most commonly mutated oncogene in cancer, with about 19% of cancer patients carrying RAS mutations. Studies on the interaction between RAS mutation and tumor immune microenvironment (TIM) have been flourishing in recent years. More and more evidence has proved that RAS signals regulate immune cells' recruitment, activation, and differentiation while assisting tumor cells to evade immune surveillance. This review concluded the direct and indirect treatment strategies for RAS mutations. In addition, we updated the underlying mechanisms by which RAS signaling modulated immune infiltration and immune escape. Finally, we discussed advances in RAS-targeted immunotherapies, including cancer vaccines and adoptive cell therapies, with a particular focus on combination strategies with personalized therapy and great potential to achieve lasting clinical benefits.

Targeting KRAS in Colorectal Cancer: A Bench to Bedside Review

Colorectal cancer (CRC) is a heterogeneous disease with a myriad of alterations at the cellular and molecular levels. Kristen rat sarcoma (KRAS) mutations occur in up to 40% of CRCs and serve as both a prognostic and predictive biomarker. Oncogenic mutations in the KRAS protein affect cellular proliferation and survival, leading to tumorigenesis through RAS/MAPK pathways. Until recently, only indirect targeting of the pathway had been investigated. There are now several KRAS allele-specific inhibitors in late-phase clinical trials, and many newer agents and targeting strategies undergoing preclinical and early-phase clinical testing. The adequate treatment of KRAS-mutated CRC will inevitably involve combination therapies due to the existence of robust adaptive resistance mechanisms in these tumors. In this article, we review the most recent understanding and findings related to targeting KRAS mutations in CRC, mechanisms of resistance to KRAS inhibitors, as well as evolving treatment strategies for KRAS-mutated CRC patients.

KRAS-Mutant Lung Cancer: Targeting Molecular and Immunologic Pathways, Therapeutic Advantages and Restrictions

RAS mutations are among the most common oncogenic mutations in human cancers. Among RAS mutations, KRAS has the highest frequency and is present in almost 30% of non-small-cell lung cancer (NSCLC) patients. Lung cancer is the number one cause of mortality among cancers as a consequence of outrageous aggressiveness and late diagnosis. High mortality rates have been the reason behind numerous investigations and clinical trials to discover proper therapeutic agents targeting KRAS. These approaches include the following: direct KRAS targeting; synthetic lethality partner inhibitors; targeting of KRAS membrane association and associated metabolic rewiring; autophagy inhibitors; downstream inhibitors; and immunotherapies and other immune-modalities such as modulating inflammatory signaling transcription factors (e.g., STAT3). The majority of these have unfortunately encountered limited therapeutic outcomes due to multiple restrictive mechanisms including the presence of co-mutations. In this review we plan to summarize the past and most recent therapies under investigation, along with their therapeutic success rate and potential restrictions. This will provide useful information to improve the design of novel agents for treatment of this deadly disease.

The role of KRAS splice variants in cancer biology

The three mammalian RAS genes (HRAS, NRAS and KRAS) encode four proteins that play central roles in cancer biology. Among them, KRAS is mutated more frequently in human cancer than any other oncogene. The pre-mRNA of KRAS is alternatively spliced to give rise to two products, KRAS4A and KRAS4B, which differ in the membrane targeting sequences at their respective C-termini. Notably, both KRAS4A and KRAS4B are oncogenic when KRAS is constitutively activated by mutation in exon 2 or 3. Whereas KRAS4B is the most studied oncoprotein, KRAS4A is understudied and until recently considered relatively unimportant. Emerging work has confirmed expression of KRAS4A in cancer and found non-overlapping functions of the splice variants. The most clearly demonstrated of these is direct regulation of hexokinase 1 by KRAS4A, suggesting that the metabolic vulnerabilities of KRAS-mutant tumors may be determined in part by the relative expression of the splice variants. The aim of this review is to address the most relevant characteristics and differential functions of the KRAS splice variants as they relate to cancer onset and progression.

Drugging KRAS: current perspectives and state-of-art review

After decades of efforts, we have recently made progress into targeting KRAS mutations in several malignancies. Known as the ‘holy grail’ of targeted cancer therapies, KRAS is the most frequently mutated oncogene in human malignancies. Under normal conditions, KRAS shuttles between the GDP-bound ‘off’ state and the GTP-bound ‘on’ state. Mutant KRAS is constitutively activated and leads to persistent downstream signaling and oncogenesis. In 2013, improved understanding of KRAS biology and newer drug designing technologies led to the crucial discovery of a cysteine drug-binding pocket in GDP-bound mutant KRAS G12C protein. Covalent inhibitors that block mutant KRAS G12C were successfully developed and sotorasib was the first KRAS G12C inhibitor to be approved, with several more in the pipeline. Simultaneously, effects of KRAS mutations on tumour microenvironment were also discovered, partly owing to the universal use of immune checkpoint inhibitors. In this review, we discuss the discovery, biology, and function of KRAS in human malignancies. We also discuss the relationship between KRAS mutations and the tumour microenvironment, and therapeutic strategies to target KRAS. Finally, we review the current clinical evidence and ongoing clinical trials of novel agents targeting KRAS and shine light on resistance pathways known so far.

Molecular Biology and Therapeutic Perspectives for K-Ras Mutant Non-Small Cell Lung Cancers

In non-small cell lung cancer (NSCLC) the most common alterations are identified in the Kirsten rat sarcoma viral oncogene homolog (KRAS) gene, accounting for approximately 30% of cases in Caucasian patients. The majority of mutations are located in exon 2, with the c.34G > T (p.G12C) change being the most prevalent. The clinical relevance of KRAS mutations in NSCLC was not recognized until a few years ago. What is now emerging is a dual key role played by KRAS mutations in the management of NSCLC patients. First, recent data report that KRAS-mutant lung AC patients generally have poorer overall survival (OS). Second, a KRAS inhibitor specifically targeting the c.34G > T (p.G12C) variant, Sotorasib, has been approved by the U.S. Food and Drug Administration (FDA) and by the European Medicines Agency. Another KRAS inhibitor targeting c.34G > T (p.G12C), Adagrasib, is currently being reviewed by the FDA for accelerated approval. From the description of the biology of KRAS-mutant NSCLC, the present review will focus on the clinical aspects of KRAS mutations in NSCLC, in particular on the emerging efficacy data of Sotorasib and other KRAS inhibitors, including mechanisms of resistance. Finally, the interaction between KRAS mutations and immune checkpoint inhibitors will be discussed.

KRAS-Mutant Non-Small-Cell Lung Cancer: From Past Efforts to Future Challenges

KRAS is the most frequently mutated oncogene identified in human cancers. Despite the numerous efforts to develop effective specific inhibitors against KRAS, this molecule has remained "undruggable" for decades. The development of direct KRAS inhibitors, such as sotorasib, the first FDA-approved drug targeting KRAS G12C, or adagrasib, was made possible with the discovery of a small pocket in the binding switch II region of KRAS G12C. However, a new challenge is represented by the necessity to overcome resistance mechanisms to KRAS inhibitors. Another area to be explored is the potential role of co-mutations in the selection of the treatment strategy, particularly in the setting of immune checkpoint inhibitors. The aim of this review was to analyze the state-of-the-art of KRAS mutations in non-small-cell lung cancer by describing the biological structure of KRAS and exploring the clinical relevance of KRAS as a prognostic and predictive biomarker. We reviewed the different treatment approaches, focusing on the novel therapeutic strategies for the treatment of KRAS-mutant lung cancers.

Ras inhibitor farnesylthiosalicylic acid conjugated with IR783 dye exhibits improved tumor-targeting and altered anti-breast cancer mechanisms in mice

Ras has long been viewed as a promising target for cancer therapy. Farnesylthiosalicylic acid (FTS), as the only Ras inhibitor has ever entered phase II clinical trials, has yielded disappointing results due to its strong hydrophobicity, poor tumor-targeting capacity, and low therapeutic efficiency. Thus, enhancing hydrophilicity and tumor-targeting capacity of FTS for improving its therapeutic efficacy is of great significance. In this study we conjugated FTS with a cancer-targeting small molecule dye IR783 and characterized the anticancer properties of the conjugate FTS-IR783. We showed that IR783 conjugation greatly improved the hydrophilicity, tumor-targeting and therapeutic potential of FTS. After a single oral administration in Balb/c mice, the relative bioavailability of FTS-IR783 was increased by 90.7% compared with FTS. We demonstrated that organic anion transporting polypeptide (OATP) and endocytosis synergistically drove the uptake of the FTS-IR783 conjugate in breast cancer MDA-MB-231 cells, resulting in superior tumor-targeting ability of the conjugate both in vitro and in vivo. We further revealed that FTS-IR783 conjugate could bind with and directly activate AMPK rather than affecting Ras, and subsequently regulate the TSC2/mTOR signaling pathway, thus achieving 2-10-fold increased anti-cancer therapeutic efficacy against 6 human breast cancer cell lines compared to FTS both in vivo and in vitro. Overall, our data highlights a promising approach for the modification of the anti-tumor drug FTS using IR783 and makes it possible to return FTS back to the clinic with a better efficacy.

Synthetic Vulnerabilities in the KRAS Pathway

Mutations in Kristen Rat Sarcoma viral oncogene (KRAS) are among the most frequent gain-of-function genetic alterations in human cancer. Most KRAS-driven cancers depend on its sustained expression and signaling. Despite spectacular recent success in the development of inhibitors targeting specific KRAS alleles, the discovery and utilization of effective directed therapies for KRAS-mutant cancers remains a major unmet need. One potential approach is the identification of KRAS-specific synthetic lethal vulnerabilities. For example, while KRAS-driven oncogenesis requires the activation of a number of signaling pathways, it also triggers stress response pathways in cancer cells that could potentially be targeted for therapeutic benefit. This review will discuss how the latest advances in functional genomics and the development of more refined models have demonstrated the existence of molecular pathways that can be exploited to uncover synthetic lethal interactions with a promising future as potential clinical treatments in KRAS-mutant cancers.

Overcoming KRAS-Mutant Lung Cancer

More than 50 years after the discovery of RAS family proteins, which harbor the most common activating mutations in cancer, the U.S. Food and Drug Administration approved the first direct allele-specific inhibitor of mutant KRAS in lung cancer. We highlight the history of discovering RAS and decades of studies targeting KRAS-driven lung cancer. A landmark article by Shokat and colleagues in 2013 elucidated allosteric inhibition of this undruggable target and paved the way for the first-in-class direct KRAS^G12C inhibitor. Although these drugs have impressive 36%-45% objective response rates with a median duration of response of 10 months, many tumors do not respond, and diverse mechanisms of resistance have already been observed; this includes new KRAS alterations, activation of alternate RTK pathway proteins, bypass pathways, and transcriptional remodeling. These resistance mechanisms can be profiled using tissue-based and plasma-based testing and help to inform clinical trial options for patients. We conclude with a discussion of research informing ongoing clinical trials to rationally test promising treatments to thwart or overcome resistance to KRAS^G12C inhibitors and target other KRAS-altered lung cancers.

Targeting KRAS Mutant in Non-Small Cell Lung Cancer: Novel Insights Into Therapeutic Strategies

Although KRAS-activating mutations represent the most common oncogenic driver in non-small cell lung cancer (NSCLC), various attempts to inhibit KRAS failed in the past decade. KRAS mutations are associated with a poor prognosis and a poor response to standard therapeutic regimen. The recent development of new therapeutic agents (i.e., adagrasib, sotorasib) that target specifically KRAS G12C in its GDP-bound state has evidenced an unprecedented success in the treatment of this subgroup of patients. Despite providing pre-clinical and clinical efficacy, several mechanisms of acquired resistance to KRAS G12C inhibitors have been reported. In this setting, combined therapeutic strategies including inhibition of either SHP2, SOS1 or downstream effectors of KRAS G12C seem particularly interesting to overcome acquired resistance. In this review, we will discuss the novel therapeutic strategies targeting KRAS G12C and promising approaches of combined therapy to overcome acquired resistance to KRAS G12C inhibitors.

Untangling the KRAS mutated lung cancer subsets and its therapeutic implications

The Kirsten rat sarcoma virus transforming protein (KRAS) mutations (predominate in codons 12, 13, and 61) and genomically drive nearly one-third of lung carcinomas. These mutations have complex functions in tumorigenesis, and influence the tumor response to chemotherapy and tyrosine kinase inhibitors resulting in a poorer patient prognosis. Recent attempts using targeted therapies against KRAS alone have met with little success. The existence of specific subsets of lung cancer based on KRAS mutations and coexisting mutations are suggested. Their interactions need further elaboration before newer promising targeted therapies for KRAS mutant lung cancers can be used as earlier lines of therapy. We summarize the existing knowledge of KRAS mutations and their coexisting mutations that is relevant to lung cancer treatment, in this review. We elaborate on the prognostic impact of clinical and pathologic characteristics of lung cancer patients associated with KRAS mutations. We briefly review the currently available techniques for KRAS mutation detection on biopsy and cytology samples. Finally, we discuss the new therapeutic strategies for targeting KRAS-mutant non-small cell lung cancer (NSCLC). These may herald a new era in the treatment of KRAS^G12Cmutated NSCLC as well as be helpful to develop demographic subsets to predict targeted therapies and prognosis of lung cancer patients.

Targeting KRAS in NSCLC: Old Failures and New Options for "Non-G12c" Patients

Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) gene mutations are among the most common driver alterations in non-small cell lung cancer (NSCLC). Despite their high frequency, valid treatment options are still lacking, mainly due to an intrinsic complexity of both the protein structure and the downstream pathway. The increasing knowledge about different mutation subtypes and co-mutations has paved the way to several promising therapeutic strategies. Despite the best results so far having been obtained in patients harbouring KRAS exon 2 p.G12C mutation, even the treatment landscape of non-p.G12C KRAS mutation positive patients is predicted to change soon. This review provides a comprehensive and critical overview of ongoing studies into NSCLC patients with KRAS mutations other than p.G12C and discusses future scenarios that will hopefully change the story of this disease.

KRAS mutation: from undruggable to druggable in cancer

Cancer is the leading cause of death worldwide, and its treatment and outcomes have been dramatically revolutionised by targeted therapies. As the most frequently mutated oncogene, Kirsten rat sarcoma viral oncogene homologue (KRAS) has attracted substantial attention. The understanding of KRAS is constantly being updated by numerous studies on KRAS in the initiation and progression of cancer diseases. However, KRAS has been deemed a challenging therapeutic target, even "undruggable", after drug-targeting efforts over the past four decades. Recently, there have been surprising advances in directly targeted drugs for KRAS, especially in KRAS (G12C) inhibitors, such as AMG510 (sotorasib) and MRTX849 (adagrasib), which have obtained encouraging results in clinical trials. Excitingly, AMG510 was the first drug-targeting KRAS (G12C) to be approved for clinical use this year. This review summarises the most recent understanding of fundamental aspects of KRAS, the relationship between the KRAS mutations and tumour immune evasion, and new progress in targeting KRAS, particularly KRAS (G12C). Moreover, the possible mechanisms of resistance to KRAS (G12C) inhibitors and possible combination therapies are summarised, with a view to providing the best regimen for individualised treatment with KRAS (G12C) inhibitors and achieving truly precise treatment.

On target: Rational approaches to KRAS inhibition for treatment of non-small cell lung carcinoma

Non-small cell lung carcinoma (NSCLC) is a leading cause of cancer death. Approximately one-third of patients with NSCLC have a KRAS mutation. KRAS^G12C, the most common mutation, is found in ~13% of patients. While KRAS was long considered 'undruggable', several novel direct KRAS^G12C inhibitors have shown encouraging signs of efficacy in phase I/II trials and one of these (sotorasib) has recently been approved by the US Food and Drug Administration. This review examines the role of KRAS mutations in NSCLC and the challenges in targeting KRAS. Based on specific KRAS biology, it reports exciting progress, exploring the use of novel direct KRAS inhibitors as monotherapy or in combination with other targeted therapies, chemotherapy, and immunotherapy.

Current therapy of KRAS-mutant lung cancer

KRAS mutations are the most frequent gain-of-function alterations in patients with lung adenocarcinoma (LADC) in the Western world. Although they have been identified decades ago, prior efforts to target KRAS signaling with single-agent therapeutic approaches such as farnesyl transferase inhibitors, prenylation inhibition, impairment of KRAS downstream signaling, and synthetic lethality screens have been unsuccessful. Moreover, the role of KRAS oncogene in LADC is still not fully understood, and its prognostic and predictive impact with regards to the standard of care therapy remains controversial. Of note, KRAS-related studies that included general non-small cell lung cancer (NSCLC) population instead of LADC patients should be very carefully evaluated. Recently, however, comprehensive genomic profiling and wide-spectrum analysis of other co-occurring genetic alterations have identified unique therapeutic vulnerabilities. Novel targeted agents such as the covalent KRAS G12C inhibitors or the recently proposed combinatory approaches are some examples which may allow a tailored treatment for LADC patients harboring KRAS mutations. This review summarizes the current knowledge about the therapeutic approaches of KRAS-mutated LADC and provides an update on the most recent advances in KRAS-targeted anti-cancer strategies, with a focus on potential clinical implications.

Targeting KRAS in non-small-cell lung cancer: recent progress and new approaches

Rat sarcoma (RAS) is the most frequently mutated oncogene in human cancer, with Kirsten rat sarcoma (KRAS) being the most commonly mutated RAS isoform. Overall, KRAS accounts for 85% of RAS mutations observed in human cancers and is present in 35% of lung adenocarcinomas (LUADs). While the use of targeted therapies and immune checkpoint inhibitors (CPIs) has drastically changed the treatment landscape of advanced non-small-cell lung cancer (NSCLC) in recent years, historic attempts to target KRAS (both direct and indirect approaches) have had little success, and no KRAS-specific targeted therapies have been approved to date for patients in this molecular subset of NSCLC. With the discovery by Ostrem, Shokat, and colleagues of the switch II pocket on the surface of the active and inactive forms of KRAS, we now have an improved understanding of the complex interactions involved in the RAS family of signaling proteins which has led to the development of a number of promising direct KRAS^G12C inhibitors, such as sotorasib and adagrasib. In previously treated patients with KRAS^G12C-mutant NSCLC, clinical activity has been shown for both sotorasib and adagrasib monotherapy; these data suggest promising new treatment options are on the horizon. With the stage now set for a new era in the treatment of KRAS^G12C-mutated NSCLC, many questions remain to be answered in order to further elucidate the mechanisms of resistance, how best to use combination strategies, and if KRAS^G12C inhibitors will have suitable activity in earlier lines of therapy for patients with advanced/metastatic NSCLC.

A Historic Perspective and Overview of H-Ras Structure, Oncogenicity, and Targeting

H-Ras is a unique isoform of the Ras GTPase family, one of the most prominently mutated oncogene families across the cancer landscape. Relative to other isoforms, though, mutations of H-Ras account for the smallest proportion of mutant Ras cancers. Yet, in recent years, there have been renewed efforts to study this isoform, especially as certain H-Ras-driven cancers, like those of the head and neck, have become more prominent. Important advances have therefore been made not only in the understanding of H-Ras structural biology but also in approaches designed to inhibit and impair its signaling activity. In this review, we outline historic and present initiatives to elucidate the mechanisms of H-Ras-dependent tumorigenesis as well as highlight ongoing developments in the quest to target this critical oncogene.

Inhibition of ERAD synergizes with FTS to eradicate pancreatic cancer cells

Background

Pancreatic ductal adenocarcinoma (PDAC), one of the most lethal cancers, is driven by oncogenic KRAS mutations. Farnesyl thiosalicylic acid (FTS), also known as salirasib, is a RAS inhibitor that selectively dislodges active RAS proteins from cell membrane, inhibiting downstream signaling. FTS has demonstrated limited therapeutic efficacy in PDAC patients despite being well tolerated.

Methods

To improve the efficacy of FTS in PDAC, we performed a genome-wide CRISPR synthetic lethality screen to identify genetic targets that synergize with FTS treatment. Among the top candidates, multiple genes in the endoplasmic reticulum-associated protein degradation (ERAD) pathway were identified. The role of ERAD inhibition in enhancing the therapeutic efficacy of FTS was further investigated in pancreatic cancer cells using pharmaceutical and genetic approaches.

Results

In murine and human PDAC cells, FTS induced unfolded protein response (UPR), which was further augmented upon treatment with a chemical inhibitor of ERAD, Eeyarestatin I (EerI). Combined treatment with FTS and EerI significantly upregulated the expression of UPR marker genes and induced apoptosis in pancreatic cancer cells. Furthermore, CRISPR-based genetic ablation of the key ERAD components, HRD1 and SEL1L, sensitized PDAC cells to FTS treatment.

Conclusion

Our study reveals a critical role for ERAD in therapeutic response of FTS and points to the modulation of UPR as a novel approach to improve the efficacy of FTS in PDAC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07967-6.

KRAS G12C-Mutant Non-Small Cell Lung Cancer: Biology, Developmental Therapeutics, and Molecular Testing

Mutation in the gene that encodes Kirsten rat sarcoma viral oncogene homolog (KRAS) is the most common oncogenic driver in advanced non-small cell lung cancer, occurring in approximately 30% of lung adenocarcinomas. Over 80% of oncogenic KRAS mutations occur at codon 12, where the glycine residue is substituted by different amino acids, leading to genomic heterogeneity of KRas-mutant tumors. The KRAS glycine-to-cysteine mutation (G12C) composes approximately 44% of KRAS mutations in non-small cell lung cancer, with mutant KRas^G12C present in approximately 13% of all patients with lung adenocarcinoma. Mutant KRas has been an oncogenic target for decades, but no viable therapeutic agents were developed until recently. However, advances in KRas molecular modeling have led to the development and clinical testing of agents that directly inhibit mutant KRas^G12C. These agents include sotorasib (AMG-510), adagrasib (MRTX-849), and JNJ-74699157. In addition to testing for known actionable oncogenic driver alterations in EGFR, ALK, ROS1, BRAF, MET exon 14 skipping, RET, and NTRK and for the expression of programmed cell-death protein ligand 1, pathologists, medical oncologists, and community practitioners will need to incorporate routine testing for emerging biomarkers such as MET amplification, ERBB2 (alias HER2), and KRAS mutations, particularly KRAS G12C, considering the promising development of direct inhibitors of KRas^G12C protein.

NMR in integrated biophysical drug discovery for RAS: past, present, and future

Mutations in RAS oncogenes occur in ~ 30% of human cancers, with KRAS being the most frequently altered isoform. RAS proteins comprise a conserved GTPase domain and a C-terminal lipid-modified tail that is unique to each isoform. The GTPase domain is a 'switch' that regulates multiple signaling cascades that drive cell growth and proliferation when activated by binding GTP, and the signal is terminated by GTP hydrolysis. Oncogenic RAS mutations disrupt the GTPase cycle, leading to accumulation of the activated GTP-bound state and promoting proliferation. RAS is a key target in oncology, however it lacks classic druggable pockets and has been extremely challenging to target. RAS signaling has thus been targeted indirectly, by harnessing key downstream effectors as well as upstream regulators, or disrupting the proper membrane localization required for signaling, by inhibiting either lipid modification or 'carrier' proteins. As a small (20 kDa) protein with multiple conformers in dynamic equilibrium, RAS is an excellent candidate for NMR-driven characterization and screening for direct inhibitors. Several molecules have been discovered that bind RAS and stabilize shallow pockets through conformational selection, and recent compounds have achieved substantial improvements in affinity. NMR-derived insight into targeting the RAS-membrane interface has revealed a new strategy to enhance the potency of small molecules, while another approach has been development of peptidyl inhibitors that bind through large interfaces rather than deep pockets. Remarkable progress has been made with mutation-specific covalent inhibitors that target the thiol of a G12C mutant, and these are now in clinical trials. Here we review the history of RAS inhibitor development and highlight the utility of NMR and integrated biophysical approaches in RAS drug discovery.

KRAS inhibition in non-small cell lung cancer: Past failures, new findings and upcoming challenges

Despite the high prevalence of Kirsten rat sarcoma (KRAS) mutations in non-small cell lung cancer (NSCLC), for a long time it has been defined as an 'undruggable target', with precision medicine not considered as an adequate approach to treat this subgroup of patients. After several years of efforts, preliminary data from early clinical trials have recently demonstrated that direct pharmacological inhibition of KRAS p.G12C mutation is possible, emerging as an effective targeted treatment for about 10-12% of patients with advanced NSCLC, with potential relevant impact on their long-term survival and quality of life. This review reports the current status of KRAS mutations detection in the Italian real-word scenario, summarises the biological basis of KRAS inhibition in NSCLC and provides an updated overview of therapeutic strategies, discussing the potential reasons for past failures and analysing the upcoming challenges related to the advent of new targeted agents in clinical practice.

Biology, pathology, and therapeutic targeting of RAS

RAS was identified as a human oncogene in the early 1980s and subsequently found to be mutated in nearly 30% of all human cancers. More importantly, RAS plays a central role in driving tumor development and maintenance. Despite decades of effort, there remain no FDA approved drugs that directly inhibit RAS. The prevalence of RAS mutations in cancer and the lack of effective anti-RAS therapies stem from RAS' core role in growth factor signaling, unique structural features, and biochemistry. However, recent advances have brought promising new drugs to clinical trials and shone a ray of hope in the field. Here, we will exposit the details of RAS biology that illustrate its key role in cell signaling and shed light on the difficulties in therapeutically targeting RAS. Furthermore, past and current efforts to develop RAS inhibitors will be discussed in depth.

Targeting KRAS Mutant Non-Small-Cell Lung Cancer: Past, Present and Future

Lung cancer is the most frequent cancer with an aggressive clinical course and high mortality rates. Most cases are diagnosed at advanced stages when treatment options are limited and the efficacy of chemotherapy is poor. The disease has a complex and heterogeneous background with non-small-cell lung cancer (NSCLC) accounting for 85% of patients and lung adenocarcinoma being the most common histological subtype. Almost 30% of adenocarcinomas of the lung are driven by an activating Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation. The ability to inhibit the oncogenic KRAS has been the holy grail of cancer research and the search for inhibitors is immensely ongoing as KRAS-mutated tumors are among the most aggressive and refractory to treatment. Therapeutic strategies tailored for KRAS+ NSCLC rely on the blockage of KRAS functional output, cellular dependencies, metabolic features, KRAS membrane associations, direct targeting of KRAS and immunotherapy. In this review, we provide an update on the most recent advances in anti-KRAS therapy for lung tumors with mechanistic insights into biological diversity and potential clinical implications.

Cancer vaccines: Targeting KRAS-driven cancers

Introduction: Mutant KRAS is a genetic driver of multiple cancers that has challenged clinical anti-cancer therapeutics in the last 3 decades. Neo-antigens encoded by KRAS mutations have been identified as tumor-specific with high immunogenicity and can be used to deliver precision cancer vaccines to promote anti-tumor immune responses. KRAS mutation-based cancer vaccines have produced encouraging preclinical and clinical results. Cancer vaccines represent a promising approach to treat KRAS-driven cancers.Areas covered: In this review, we summarize the development and progress of vaccines targeting KRAS and evaluate their potential benefits and obstacles in the current landscape of therapy for KRAS-driven cancers.Expert opinion: KRAS mutation-based cancer vaccines can induce immunogenicity in patients with KRAS-driven cancers. However, the mechanisms of tumor suppression including cellular and molecular factors within the tumor microenvironment may limit vaccine efficacy. Combining KRAS-driven therapeutic cancer vaccines with other methods and adjuvants can circumvent immunosuppression and promote therapeutic successes.

Role of oncogenic KRAS in the diagnosis, prognosis and treatment of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is predicted to be the second most common cause of death within the next 10 years. The prognosis for this disease is poor despite diagnostic progress and new chemotherapeutic regimens. The oncogenic KRAS mutation is the major event in pancreatic cancer; it confers permanent activation of the KRAS protein, which acts as a molecular switch to activate various intracellular signalling pathways and transcription factors inducing cell proliferation, migration, transformation and survival. Several laboratory methods have been developed to detect KRAS mutations in biological samples, including digital droplet PCR (which displays high sensitivity). Clinical studies have revealed that a KRAS mutation assay in fine-needle aspiration material combined with cytopathology increases the sensitivity, accuracy and negative predictive value of cytopathology for a positive diagnosis of pancreatic cancer. In addition, the presence of KRAS mutations in serum and plasma (liquid biopsies) correlates with a worse prognosis. The presence of mutated KRAS can also have therapeutic implications, whether at the gene level per se, during its post-translational maturation, interaction with nucleotides and after activation of the various oncogenic signals. Further pharmacokinetic and toxicological studies on new molecules are required, especially small synthetic molecules, before they can be used in the therapeutic arsenal for pancreatic ductal adenocarcinoma.

Recent Advances in Developing K-Ras Plasma Membrane Localization Inhibitors

The Ras proteins play an important role in cell growth, differentiation, proliferation and survival by regulating diverse signaling pathways. Oncogenic mutant K-Ras is the most frequently mutated class of Ras superfamily that is highly prevalent in many human cancers. Despite intensive efforts to combat various K-Ras-mutant-driven cancers, no effective K-Ras-specific inhibitors have yet been approved for clinical use to date. Since K-Ras proteins must be associated to the plasma membrane for their function, targeting K-Ras plasma membrane localization represents a logical and potentially tractable therapeutic approach. Here, we summarize the recent advances in the development of K-Ras plasma membrane localization inhibitors including natural product-based inhibitors achieved from high throughput screening, fragment-based drug design, virtual screening, and drug repurposing as well as hit-to-lead optimizations.

Targeting Mutant KRAS for Anticancer Therapy

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Over the past decades, designing therapeutic strategies to target KRAS-mutant cancers, which is one of the most frequent mutant oncogenes among all cancer types, have proven unsuccessful regardless of many concerted attempts. There are key challenges for KRAS-mutant anticancer therapy, as the complex cellular processes involved in KRAS signaling has present. Herein, we highlight the emerging therapeutic approaches for inhibiting KRAS signaling and blocking KRAS functions, in hope to serve as a more effective guideline for future development of therapeutics.

PEG-Derivatized Dual-Functional Nanomicelles for Improved Cancer Therapy

Polymeric micelles have attracted considerable attention for effective delivery of poorly water-soluble cancer drugs. Polyethylene glycol (PEG), which has been approved for human use by the US Food and Drug Administration, is the most commonly used hydrophilic component of polymeric micelles because it is biocompatible and biodegradable. One disadvantage of traditional polymeric micelles is that they include a large amount of inert carrier materials, which do not contribute to therapeutic activity but increase cost and toxicity risk. A better alternative may be "dual-functional" micellar carriers, in which the hydrophobic carrier material (conjugated to PEG) has intrinsic therapeutic activity that complements, or even synergizes with, the antitumor activity of the drug cargo. This review summarizes recent progress in the development of PEG-derivatized dual-functional nanomicelles and surveys the evidence of their feasibility and promise for cancer therapy.

Drugging the Small GTPase Pathways in Cancer Treatment: Promises and Challenges

Small GTPases are a family of low molecular weight GTP-hydrolyzing enzymes that cycle between an inactive state when bound to GDP and an active state when associated to GTP. Small GTPases regulate key cellular processes (e.g., cell differentiation, proliferation, and motility) as well as subcellular events (e.g., vesicle trafficking), making them key participants in a great array of pathophysiological processes. Indeed, the dysfunction and deregulation of certain small GTPases, such as the members of the Ras and Arf subfamilies, have been related with the promotion and progression of cancer. Therefore, the development of inhibitors that target dysfunctional small GTPases could represent a potential therapeutic strategy for cancer treatment. This review covers the basic biochemical mechanisms and the diverse functions of small GTPases in cancer. We also discuss the strategies and challenges of inhibiting the activity of these enzymes and delve into new approaches that offer opportunities to target them in cancer therapy.

Epidermal growth factor receptor controls glycogen phosphorylase in T cells through small GTPases of the RAS family

We recently uncovered a regulatory pathway of the muscle isoform of glycogen phosphorylase (PYGM) that plays an important role in regulating immune function in T cells. Here, using various enzymatic, pulldown, and immunoprecipitation assays, we describe signaling cross-talk between the small GTPases RAS and RAP1A, member of RAS oncogene family (RAP1) in human Kit 225 lymphoid cells, which, in turn, is regulated by the epidermal growth factor receptor (EGFR). We found that this communication bridge is essential for glycogen phosphorylase (PYG) activation through the canonical pathway because this enzyme is inactive in the absence of adenylyl cyclase type 6 (ADCY6). PYG activation required stimulation of both exchange protein directly activated by cAMP 2 (EPAC2) and RAP1 via RAS and ADCY6 phosphorylation, with the latter being mediated by Raf-1 proto-oncogene, Ser/Thr kinase (RAF1). Consistent with this model, PYG activation was EGFR-dependent and may be initiated by the constitutively active form of RAS. Consequently, PYG activation in Kit 225 T cells could be blocked with specific inhibitors of RAS, EPAC, RAP1, RAF1, ADCY6, and cAMP-dependent protein kinase. Our results establish a new paradigm for the mechanism of PYG activation, which depends on the type of receptor involved.

Aberrant Neuronal Cell Cycle Re-Entry: The Pathological Confluence of Alzheimer's Disease and Brain Insulin Resistance, and Its Relation to Cancer

Aberrant neuronal cell cycle re-entry (CCR) is a phenomenon that precedes and may mechanistically lead to a majority of the neuronal loss observed in Alzheimer's disease (AD). Recent developments concerning the regulation of aberrant neuronal CCR in AD suggest that there are potential intracellular signaling "hotspots" in AD, cancer, and brain insulin resistance, the latter of which is characteristically associated with AD. Critically, these common signaling nodes across different human diseases may represent currently untapped therapeutic opportunities for AD. Specifically, repurposing of existing US Food and Drug Administration-approved pharmacological agents, including experimental therapeutics that target the cell cycle in cancer, may be an innovative avenue for future AD-directed drug discovery and development. In this review we discuss overlapping aspects of AD, cancer, and brain insulin resistance from the perspective of neuronal CCR, and consider strategies to exploit them for prevention or therapeutic intervention of AD.

iRGD-guided Tumor-penetrating Nanocomplexes for Therapeutic siRNA Delivery to Pancreatic Cancer

Pancreatic cancer is one of the leading causes of cancer-related death, with 5-year survival of 8.5%. The lack of significant progress in improving therapy reflects our inability to overcome the desmoplastic stromal barrier in pancreatic ductal adenocarcinoma (PDAC) as well as a paucity of new approaches targeting its genetic underpinnings. RNA interference holds promise in targeting key mutations driving PDAC; however, a nucleic acid delivery vehicle that homes to PDAC and breaches the stroma does not yet exist. Noting that the cyclic peptide iRGD mediates tumor targeting and penetration through interactions with αvβ3/5 integrins and neuropilin-1, we hypothesized that "tandem" peptides combining a cell-penetrating peptide and iRGD can encapsulate siRNA to form tumor-penetrating nanocomplexes (TPN) capable of delivering siRNA to PDAC. The use of directly conjugated iRGD is justified by receptor expression patterns in human PDAC biopsies. In this work, we optimize iRGD TPNs with polyethylene glycol (PEG)-peptide conjugates for systemic delivery to sites of disease. We show that TPNs effectively knockdown siRNA targets in PDAC cell lines and in an immunocompetent genetically engineered mouse model of PDAC. Furthermore, we validate their tumor-penetrating ability in three-dimensional organoids and autochthonous tumors. In murine therapeutic trials, TPNs delivering anti-Kras siRNA significantly delay tumor growth. Thus, iRGD TPNs hold promise in treating PDAC by not only overcoming physical barriers to therapy, but by leveraging the stroma to achieve knockdown of the gold-standard genetic target. Moreover, the modular construction of this delivery platform allows for facile adaptation to future genetic target candidates in pancreatic cancer. Mol Cancer Ther; 17(11); 2377-88. ©2018 AACR.

Is Ras a potential target in treatment against cutaneous squamous cell carcinoma?

Hyperactive retrovirus-associated DNA sequence (Ras) genes have been found in human cancers and are involved in cancer pathogenesis. Salirasib, one anti-Ras compound, was reported to exhibit antitumoral effects, but its role remains unclear in cutaneous squamous cell carcinoma (cSCC). In our study, salirasib treatment led to deregulation of c-Raf, ERK and Akt signaling, blockage of MTOR signaling, interruption on Beclin 1-related autophagy regulation, activation of apoptosis and down-regulation of some cell cycle regulatory proteins in primary human epidermal keratinocyte (HEK)s, but did not exhibit similar effects in the human cSCC cell line COLO-16. MEK inhibitor U0126 can lead to dephosphorylation of MTOR and Rictor in COLO-16 cells; however, c-Raf was not yet down-regulated after salirasib treatment in the presence of U0126. Furthermore, we verified that the Ras activity could be suppressed by salirasib, and there was no loss-of-function mutation in c-Raf in HEKs and COLO-16 cells. In summary, salirasib does not exhibit antitumoral effects in the cSCC cells in assays in vitro. We speculated that the disability of signaling transmission from Ras to c-Raf in COLO-16 cells might contribute to the ineffective performance of salirasib.

Targeting oncogenic drivers in lung cancer: Recent progress, current challenges and future opportunities

Targeted therapies have changed the landscape of treatments for non-small cell lung cancer (NSCLC). Specific targeted therapies have been approved for NSCLC patients harboring genetic alterations in four oncogenes, and agents targeting additional oncogenic drivers are under investigation. Standard first-line chemotherapy has been supplanted by these targeted therapies due to superior efficacy and lower toxicity. Despite excellent response rates and durable responses in some cases, most patients experience relapse within a few years due to the development of acquired drug resistance. Next generation targeted therapies are being developed to overcome drug resistance and extend the duration of therapy. In this review, we summarize the current treatment strategies for the major targetable oncogenic mutations/alterations in NSCLC and discuss the mechanisms leading to acquired drug resistance.