Worldwide Prevalence and Clinical Characteristics of RAS Mutations in Head and Neck Cancer: A Systematic Review and Meta-Analysis

Importance: There is considerable variation among different studies for the prevalence of RAS mutations in head and neck cancer (HNC) patients. In light of the development of RAS inhibitors, a reliable assessment of the prevalence of RAS mutations and their correlation with the clinical features of patients with HNC is crucially needed. Objective: To assess the worldwide prevalence of HRAS, KRAS, and NRAS mutations in HNC in the relation to geographical region, anatomical site(s) of the tumor(s) and clinical features. Data Sources: A systematic search of the PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials databases was performed to identify studies published since January 2000. Data were analyzed between June and September 2021. Study Selection: Studies that included mutational analyses of at least one of the target genes and reported the prevalence and frequency of mutations as an outcome measure were included. Studies including less than ten patients or were conducted before year 2000 were excluded. Data Extraction and Synthesis: Two researchers independently reviewed the literature according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guidelines. Random-effects models were applied to results with high heterogeneity. Otherwise, fixed-effects models were used for the analyses. Dichotomous variables were pooled as odds ratios (OR). Main Outcome(s) and Measure(s): The primary outcome was mutation prevalence. Secondary outcomes included the location of the mutated codon and amino acid substitution. Results: The estimated mutation rate is highest for HRAS (7%), followed by KRAS (2.89%) and NRAS (2.20%). HRAS prevalence in South Asia (15.28%) is twice as high as the global estimate. HRAS mutations are more prevalent in oral cavity and salivary gland tumors. In contrast, KRAS mutations are found more frequently in sinonasal tumors, and NRAS mutations are found chiefly in tumors of the nasopharynx. OR analyses show a significant association between HRAS mutations and a high tumor stage (OR=3.63). In addition, there is a significant association between HPV-positive status and KRAS mutations (OR=2.09). Conclusions and Relevance: RAS mutations occur in a subset of HNC patients and their prevalence varies according to geography, tumors anatomical site, stage, and HPV status. This meta-analysis provides support for their potential as viable therapeutic targets in HNC patients.

Association of RAS mutations with early progression after first-line systemic therapy in patients with initially unresectable colorectal cancer liver metastasis

Purpose Patients with initially unresectable colorectal cancer with liver metastases (IU-CRLM) need to undergo first-line systemic therapy with the aid of chemotherapy. However, the driver gene attributed to early progression in IU-CRLM patients after first-line systemic therapy remains unclear. Our study explored the RAS mutation status related to early progression in IU-CRLM patients. Methods A total of 193 IU-CRLM patients with RAS status detection were retrospectively enrolled from December 2012 to January 2020. We defined early progression as tumour progression within 6 months after first-line systemic therapy. Univariate and multivariate logistic regression for early progression were implemented to identify the risk factors. Results RAS mutations were found in 51 (26.0%) IU-CRLM patients. A total of 107 (55.4%) patients were confirmed to have early progression after first-line systemic therapy. RAS mutation was significantly related to early disease progression (66.7% vs. 49.3%, P=0.033). Logistic analysis results showed that RAS mutation (OR=2.962, 95% CI 1.354-6.478, P=0.007) was an independent risk factor for early disease progression. Conclusions Mutated RAS was an important risk factor for early progression in IU-CRLM patients after first-line systemic therapy.

Significance of RAS Mutations in Thyroid Benign Nodules and Non-Medullary Thyroid Cancer

Thyroid nodules are detected in up to 60% of people by ultrasound examination. Most of them are benign nodules requiring only follow up, while about 4% are carcinomas and require surgery. Malignant nodules can be diagnosed by the fine-needle aspiration cytology (FNAC), which however yields an indeterminate result in about 30% of the cases. Testing for RAS mutations has been proposed to refine indeterminate cytology. However, the new entity of non-invasive follicular thyroid neoplasm, considered as having a benign evolution and frequently carrying RAS mutations, is expected to lower the specificity of this mutation. The aggressive behavior of thyroid cancer with RAS mutations, initially reported, has been overturned by the recent finding of the cooperative role of TERT mutations. Although some animal models support the carcinogenic role of RAS mutations in the thyroid, evidence that adenomas harboring these mutations evolve in carcinomas is lacking. Their poor specificity and sensitivity make the clinical impact of RAS mutations on the management of thyroid nodules with indeterminate cytology unsatisfactory. Evidence suggests that RAS mutation-positive benign nodules demand a conservative treatment. To have a clinical impact, RAS mutations in thyroid malignancies need not to be considered alone but rather together with other genetic abnormalities in a more general context.

RAS-inhibiting biologics identify and probe druggable pockets including an SII-α3 allosteric site

RAS mutations are the most common oncogenic drivers across human cancers, but there remains a paucity of clinically-validated pharmacological inhibitors of RAS, as druggable pockets have proven difficult to identify. Here, we identify two RAS-binding Affimer proteins, K3 and K6, that inhibit nucleotide exchange and downstream signaling pathways with distinct isoform and mutant profiles. Affimer K6 binds in the SI/SII pocket, whilst Affimer K3 is a non-covalent inhibitor of the SII region that reveals a conformer of wild-type RAS with a large, druggable SII/α3 pocket. Competitive NanoBRET between the RAS-binding Affimers and known RAS binding small-molecules demonstrates the potential to use Affimers as tools to identify pharmacophores. This work highlights the potential of using biologics with small interface surfaces to select unseen, druggable conformations in conjunction with pharmacophore identification for hard-to-drug proteins.

Digital PCR-based cell-free DNA K-Ras mutations analysis and clinical implication in pancreatic cancer.

e16215 Background: Pancreatic cancer is one of the most fatal cancers worldwide. In addition to patients presenting later in the disease, limitations in current testing modalities pose a challenge to early diagnosis and treatment. Somatic mutations of the K-Ras gene have been suggested as a key driver of pancreatic carcinogenesis and thus proposed as a biomarker for diagnosis and therapy. Majority of these studies utilize tissue-based methods for analyzing K-Ras mutations. In recent years, liquid biopsy assay, in particular, analysis of cell-free DNA (cfDNA), has emerged as a promising noninvasive diagnostic approach in oncology, with the respect to the identification of minimal residual diseases, monitoring treatment response, detection recurrence and metastasis, and identification of chemo-resistance mechanisms. The application of digital PCR based plasma cfDNA K-Ras mutation assay in pancreatic cancer has not been reported. Methods: We included patients who underwent evaluation of a pancreatic lesion detected by conventional radiography (CT/MRI) and confirmed by endoscopic ultrasound (EUS) and biopsy. The biopsies from pancreatic tissues were formalin-fixed and paraffin-embedded (FFPE) for pathological diagnosis, and the total DNA was extracted from the FFPE slides. In addition, matched blood from the same patient was collected at the time of biopsy, and plasma cfDNA was extracted. Both DNA quality and concentration were evaluated. 4.0 ng of DNA was used for droplet digital PCR (ddPCR) analysis. K-Ras G12D, G12V, G12R, G12C, G12A, G12S, and G13D mutations were analyzed by multiplexed assay reagents. The sensitivity cut-off of the multiplexed K-Ras G12/G13 assay was 1.0%. Results: cfDNA could be detected in the initiation of pathological diagnosis. Among the twelve patients with pancreatic lesions, eight (67%) were pancreatic ductal adenocarcinoma (PDAC) (head (4), body (2), tail (2) of the pancreas), one was acute pancreatitis, one was a tail cyst and two were unspecified non-malignant lesions. All the eight PDAC (100%) FFPE tissues exhibited K-Ras G12/13 mutations (Scores: 4.2-41.5%), while none of the non-malignant lesions (0%) demonstrated K-Ras mutations. Interestingly, K-Ras mutations were detected from seven of the eight PDAC patient’s plasma cfDNA (87.5%) (Scores: 1.2-20.7%) while the plasma cfDNA from patients with non-malignant lesions did not show any positive K-Ras mutations. Conclusions: Digital PCR-based plasma cfDNA assay for K-Ras mutation is a promising tool for diagnosis of PDAC and is comparable to tissue-based assays. Larger prospective studies can substantiate this and explore their roles in the prediction and early detection of recurrence of PDAC.

Open-label phase 1 study evaluating the tolerability and anti-tumor activity of selinexor and pembrolizumab in colorectal cancer.

e15579 Background: Colorectal cancer (CRC) is the fourth leading cause of cancer-related deaths worldwide and is heterogenous in its molecular features. Checkpoint inhibitors (CPIs) are approved for only about 5% of unresectable or metastatic CRC with MSI-high (MSI-H)/deficient MMR (dMMR); however, they do not benefit the majority of advanced CRC patients. Selinexor is a first-in-class, oral selective inhibitor of nuclear export (SINE) compound with demonstrated activity in cancers with RAS mutations which are found in ̃50% of CRC. This study aims to evaluate the combination of selinexor with pembrolizumab, an anti-PD-L1 CPI, in chemotherapy refractory CRC. Methods: This phase 1/2, open-label study enrolled patients with advanced/metastatic CRC with progression after prior chemotherapy (1-3 lines for KRAS wild-type (wt), 1-2 for KRAS mutant (mut)), initially into a selinexor monotherapy period to evaluate bioavailability/bioequivalence of a new selinexor formulation, followed by a combination therapy where patients were treated with selinexor 80 mg PO QW and pembrolizumab 200 mg IV every 3 weeks. Patients were assessed for anti-tumor activity, safety, and tolerability of the combination therapy. Results: Enrollment in this study has been completed, and 29 patients have received at least 1 dose of combination therapy: median age was 56 years, 19 (65.5%) male, and 15 (51.7%) have RAS mutations. Median number of lines of prior antineoplastic therapies was 2. Median duration of combination treatment is 39 days (range: 1-246 days). Seventeen patients (58.6%) discontinued therapy mostly due to progressive disease, and 18 patients are evaluable for response. Best response was stable disease in 7 patients (6 of them (85.7%) had RAS mut CRC), and progressive disease in 11 patients (8 of them (72.7%) had RAS wt CRC. Median progression free survival (PFS) is 120 days for patients with RAS mut CRC and 41 days for those with RAS wt CRC. Notably, none of the RAS mut had MSI-H/dMMR CRC while one RAS wt with SD had MSI-H/dMMR CRC. The most common treatment-emergent adverse events (total; ≥Grade 3) were nausea (72.4%; 0%), vomiting (41.4%; 0%), decreased appetite (34.5%; 0%), and fatigue (34.5%; 10.3%). Seven patients (24.1%) had at least 1 treatment-emergent serious adverse event. Conclusions: Selinexor in combination with pembrolizumab has demonstrated disease control in patients with chemotherapy refractory advanced/metastatic CRC. Greater anti-tumor activity was observed in patients with RAS mutations despite absence of MSI-H/dMMR. The therapy was well tolerated with no unanticipated adverse events observed. These results warrant further investigation of selinexor in combination with pembrolizumab in CRC, particularly in CRC with RAS mutations. Clinical trial information: NCT04256707.