KRAS-mutation status dependent effect of zoledronic acid in human non-small cell cancer preclinical models

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.

KRASG12C mutant lung adenocarcinoma: unique biology, novel therapies and new challenges

KRAS mutant lung cancer is the most prevalent molecular subclass of adenocarcinoma (LUAD), which is a heterogenous group depending on the mutation-type which affects not only the function of the oncogene but affects the biological behavior of the cancer as well. Furthermore, KRAS mutation affects radiation sensitivity but leads also to bevacizumab and bisphosphonate resistance as well. It was highly significant that allele specific irreversible inhibitors have been developed for the smoking associated G12C mutant KRAS (sotorasib and adagrasib). Based on trial data both sotorasib and adagrasib obtained conditional approval by FDA for the treatment of previously treated advanced LUAD. Similar to other target therapies, clinical administration of KRASG12C inhibitors (sotorasib and adagrasib) resulted in acquired resistance due to various genetic changes not only in KRAS but in other oncogenes as well. Recent clinical studies are aiming to increase the efficacy of G12C inhibitors by novel combination strategies.

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.

K-Ras prenylation as a potential anticancer target

KRAS is one of the most commonly mutated oncogene and a negative predictive factor for a number of targeted therapies. Therefore, the development of targeting strategies against mutant KRAS is urgently needed. One potential strategy involves disruption of K-Ras membrane localization, which is necessary for its proper function. In this review, we summarize the current data about the importance of membrane-anchorage of K-Ras and provide a critical evaluation of this targeting paradigm focusing mainly on prenylation inhibition. Additionally, we performed a RAS mutation-specific analysis of prenylation-related drug sensitivity data from a publicly available database (https://depmap.org/repurposing/) of three classes of prenylation inhibitors: statins, N-bisphosphonates, and farnesyl-transferase inhibitors. We observed significant differences in sensitivity to N-bisphosphonates and farnesyl-transferase inhibitors depending on KRAS mutational status and tissue of origin. These observations emphasize the importance of factors affecting efficacy of prenylation inhibition, like distinct features of different KRAS mutations, tissue-specific mutational patterns, K-Ras turnover, and changes in regulation of prenylation process. Finally, we enlist the factors that might be responsible for the large discrepancy between the outcomes in preclinical and clinical studies including methodological pitfalls, the incomplete understanding of K-Ras protein turnover, and the variation of KRAS dependency in KRAS mutant tumors.

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.

The effects of bisphosphonate and radiation therapy in bone-metastatic lung adenocarcinoma: the impact of KRAS mutation

Background

KRAS mutation is the most common genetic alteration in lung adenocarcinoma (LADC) in Western countries and is associated with worse outcome in bone-metastatic cases. Yet, to date, no effective treatment guidelines were developed for these patients. Accordingly, our aim was to investigate the impact of KRAS mutation on bisphosphonate (BTx) and radiation therapy (RTx) in bone-metastatic LADC patients.

Methods

Clinicopathological variables of 134 consecutive LADC patients with bone metastases at diagnosis and known KRAS status were retrospectively analyzed. The effects of BTx, RTx and KRAS mutation on overall survival (OS) were investigated.

Results

Of the total cohort, 93 patients were identified as KRAS wild-type (WT) (69.4%) and 41 (30.6%) as KRAS mutant patients. The presence of KRAS mutation was associated with significantly reduced median OS (5.1 vs. 10.2 months in KRAS WT patients; P=0.008). Irrespective of KRAS mutational status both BTx (P=0.007) and RTx (P=0.021) conferred a significant benefit for OS. Notably, however, when analyzing the patients with KRAS-mutant and KRAS WT tumors separately, the benefit from BTx and RTx on OS remained statistically significant only in KRAS WT patients (P=0.032 and P=0.031, respectively).

Conclusions

KRAS mutation is a strong negative prognostic factor in bone-metastatic LADC patients. Both BTx and RTx can increase the OS with a pronounced benefit for patients with KRAS WT tumors. Altogether, KRAS mutational status should be considered during therapeutic decision making in bone-metastatic LADC patients.

Next Generation Lipophilic Bisphosphonate Shows Antitumor Effect in Colorectal Cancer In Vitro and In Vivo

Bisphosphonates, despite proven antitumor effect in vitro in many tumor types, are currently used only for treatment of osteoporosis and bone metastasis. Colorectal cancer is the third most commonly diagnosed type of cancer and lacks targeted therapy for RAS or RAF mutation carrying cases. A new lipophilic bisphosphonate showed promising results in lung cancer models, but their effect on colorectal cancer cells was not investigated excessively. Antitumor effects and impact on RAS-related signalization of zoledronic acid (ZA) and a lipophilic bisphosphonate (BPH1222) were investigated on 7 human colorectal cancer cell lines in vitro and in vivo. Furthermore, mutant KRAS dependent effect of prenylation inhibition was investigated using isogeneic cell lines. Both bisphosphonates reduced cell viability in vitro in a dose-dependent manner. Both compounds changed cell cycle distribution similarly by increasing the proportion of cells either in the S or in the subG1 phase or both. However, BPH1222 exerted higher inhibitory effect on spheroid growth than ZA. Interestingly, we found profound alterations in phosphorylation level of Erk and S6 proteins upon ZA or BPH1222 treatment. Furthermore, investigation of a mutant KRAS isogeneic model system suggests that the drugs interfere also with the mutant KRAS proteins. In vivo experiments with KRAS mutant xenograft model also revealed growth inhibitory potential of bisphosphonate treatment. Our results show that lipophilic bisphosphonates might extend the therapeutic spectrum of bisphosphonate drugs and could be considered as additional treatment approaches in colorectal cancer.

Anti-Tumor Effects of Low Dose Zoledronate on Lung Cancer-Induced Spine Metastasis

Zoledronate (Zol) is an anti-resorptive/tumoral agent used for the treatment of many cancers including spinal bone metastasis. High systemic administration of a single dose is now the standard clinical care, yet it has been associated with several side effects. Here, we aimed to evaluate the effects of lower doses Zol on lung cancer and lung cancer-induced bone metastasis cells over a longer time period. Human lung cancer (HCC827) and three bone metastases secondary to lung cancer (BML1, BML3 and BML4) cells were treated with Zol at 1, 3 and 10 µM for 7 days and then assessed for cell proliferation, migration, invasion and apoptosis. Low Zol treatment significantly decreased cell proliferation (1, 3 and 10 µM), migration (3 and 10 µM) and invasion (10 µM) while increasing apoptosis (10 µM) in lung cancer and metastatic cells. Our data exploits the potential of using low doses Zol for longer treatment periods and reinforces this approach as a new therapeutic regimen to impede the development of metastatic bone cancer while limiting severe side effects following high doses of systemic drug treatment.

Prognostic effects of osteoclast inhibitors in extensive stage small cell lung cancer patients with bone metastases

Bone metastases (BM) often induce skeletal-related events (SREs) and contribute to poor prognoses in patients with cancer. Osteoclast inhibitors (OIs), such as bisphosphonates (BPs) and denosumab, reportedly prevent SREs and improve quality of life in patients with non-small cell lung cancer and BM, but have not been tested in extensive stage small cell lung cancer (ES-SCLC) patients. From 238 SCLC patient records, the present study reviewed those of 58 BM patients, including 23 who were treated with OIs (OIs group) and 35 who were untreated (untreated group). Patient backgrounds were balanced between groups using propensity score matching, and survival curves were compared using the log-rank test. The median overall survival (OS) times were 8.41 and 12.52 months in untreated and OIs groups, respectively, but these did not differ significantly between groups (log-rank test, P=0.409). The 1-year OS rate was higher in the OIs group (56.1%) when compared with the control group (22.6%). The results indicated that OIs tend to prolong the short term survival of ES-SCLC patients with BM. To the best of our knowledge, this is the first study to examine the prognostic effects of OIs in SCLC patients. The results of the present study may highlight the possibility that OIs improve the prognosis of ES-SCLC patients with BM.

Super enhancer associated RAI14 is a new potential biomarker in lung adenocarcinoma

Purpose

Tyrosine kinase inhibitors (TKIs) are widely used to treat lung adenocarcinoma patients with EGFR mutations or ALK-fusions. However, patients with wild-type genes or TKIs-resistant mutations lack effective therapeutic targets. Extensive studies reveal that super enhancer (SE), a large cis-regulatory element, is associated with key oncogenes in a variety of cancers. By comparing the effect of SE on lung adenocarcinoma cell lines with normal cell line, this work attempts to find new biomarkers and potential therapeutic targets for lung adenocarcinoma.

Experimental Design

Chromatin Immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq) of H3K27ac (acetylation on lysine 27 of histone 3) was performed in lung adenocarcinoma cell lines SPC-A1 and SCH-1153. The differences in SE distribution were then analyzed among SPC-A1, SCH-1153, A549 and normal human lung fibroblasts (NHLF) to identify SE-associated oncogenes. The expression of SE-associated oncogenes was then detected by RNA-seq and further verified in 71 patients by real-time PCR.

Results

SE associated with many new oncogenes in lung adenocarcinoma, among which, RAI14 was up-regulated in A549 and 31 of 71 patients. High expression of RAI14 could inhibit cell proliferation, indicating its potential as a new biomarker for lung adenocarcinoma.