KRAS A146 Mutations Are Associated With Distinct Clinical Behavior in Patients With Colorectal Liver Metastases

Novel druggable space in human KRAS G13D discovered using structural bioinformatics and a P-loop targeting monoclonal antibody

KRAS belongs to a family of small GTPases that act as binary switches upstream of several signalling cascades, controlling proliferation and survival of cells. Mutations in KRAS drive oncogenesis, especially in pancreatic, lung, and colorectal cancers (CRC). Although historic attempts at targeting mutant KRAS with small molecule inhibitors have proven challenging, there are recent successes with the G12C, and G12D mutations. However, clinically important RAS mutations such as G12V, G13D, Q61L, and A146T, remain elusive drug targets, and insights to their structural landscape is of critical importance to develop novel, and effective therapeutic concepts. We present a fully open, P-loop exposing conformer of KRAS G13D by X-ray crystallography at 1.4-2.4 Å resolution in Mg2+-free phosphate and malonate buffers. The G13D conformer has the switch-I region displaced in an upright position leaving the catalytic core fully exposed. To prove that this state is druggable, we developed a P-loop-targeting monoclonal antibody (mAb). The mAb displayed high-affinity binding to G13D and was shown using high resolution fluorescence microscopy to be spontaneously taken up by G13D-mutated HCT 116 cells (human CRC derived) by macropinocytosis. The mAb inhibited KRAS signalling in phosphoproteomic and genomic studies. Taken together, the data propose novel druggable space of G13D that is reachable in the cellular context. It is our hope that these findings will stimulate attempts to drug this fully open state G13D conformer using mAbs or other modalities.

KRAS Mutation Subtypes and Their Association with Other Driver Mutations in Oncogenic Pathways

The KRAS mutation stands out as one of the most influential oncogenic mutations, which directly regulates the hallmark features of cancer and interacts with other cancer-causing driver mutations. However, there remains a lack of precise information on their cooccurrence with mutated variants of KRAS and any correlations between KRAS and other driver mutations. To enquire about this issue, we delved into cBioPortal, TCGA, UALCAN, and Uniport studies. We aimed to unravel the complexity of KRAS and its relationships with other driver mutations. We noticed that G12D and G12V are the prevalent mutated variants of KRAS and coexist with the TP53 mutation in PAAD and CRAD, while G12C and G12V coexist with LUAD. We also noticed similar observations in the case of PIK3CA and APC mutations in CRAD. At the transcript level, a positive correlation exists between KRAS and PIK3CA and between APC and KRAS in CRAD. The existence of the co-mutation of KRAS and other driver mutations could influence the signaling pathway in the neoplastic transformation. Moreover, it has immense prognostic and predictive implications, which could help in better therapeutic management to treat cancer.

Exploring Co-occurring POLE Exonuclease and Non-exonuclease Domain Mutations and Their Impact on Tumor Mutagenicity

POLE driver mutations in the exonuclease domain (ExoD driver) are prevalent in several cancers, including colorectal cancer and endometrial cancer, leading to dramatically ultra-high tumor mutation burden (TMB). To understand whether POLE mutations that are not classified as drivers (POLE Variant) contribute to mutagenesis, we assessed TMB in 447 POLE-mutated colorectal cancers, endometrial cancers, and ovarian cancers classified as TMB-high ≥10 mutations/Mb (mut/Mb) or TMB-low <10 mut/Mb. TMB was significantly highest in tumors with "POLE ExoD driver plus POLE Variant" (colorectal cancer and endometrial cancer, P < 0.001; ovarian cancer, P < 0.05). TMB increased with additional POLE variants (P < 0.001), but plateaued at 2, suggesting an association between the presence of these variants and TMB. Integrated analysis of AlphaFold2 POLE models and quantitative stability estimates predicted the impact of multiple POLE variants on POLE functionality. The prevalence of immunogenic neoepitopes was notably higher in the "POLE ExoD driver plus POLE Variant" tumors. Overall, this study reveals a novel correlation between POLE variants in POLE ExoD-driven tumors, and ultra-high TMB. Currently, only select pathogenic ExoD mutations with a reliable association with ultra-high TMB inform clinical practice. Thus, these findings are hypothesis-generating, require functional validation, and could potentially inform tumor classification, treatment responses, and clinical outcomes.

SIGNIFICANCE

Somatic POLE ExoD driver mutations cause proofreading deficiency that induces high TMB. This study suggests a novel modifier role for POLE variants in POLE ExoD-driven tumors, associated with ultra-high TMB. These data, in addition to future functional studies, may inform tumor classification, therapeutic response, and patient outcomes.

Vitamin C intake and colorectal cancer survival according to KRAS and BRAF mutation: a prospective study in two US cohorts

BACKGROUND

The associations of vitamin C intake with colorectal cancer (CRC) survival according to tumour KRAS or BRAF mutation status remain unclear.

METHODS

We used the inverse probability weighted multivariable Cox proportional hazards regression model to calculate the hazard ratio (HR) of mortality, and spline analysis to evaluate the dose-response relationship in the Nurses' Health Study and Health Professionals Follow-up Study. We also assessed SLC2A1 mRNA expression according to KRAS or BRAF mutation in the TCGA database.

RESULTS

During an average of 12.0 years of follow-up, we documented 2,096 CRC cases, of which 703 cases had KRAS and BRAF mutation data. The association between total vitamin C intake and CRC-specific mortality suggestively differed according to KRAS or BRAF mutation status (Pinteraction = 0.04), with the multivariable HR (95% CI) per 400 mg/day increase in vitamin C intake for CRC-specific mortality of 1.07 (0.87-1.32, Ptrend = 0.52) in cases with both wild type and 0.74 (0.55-1.00, Ptrend < 0.05) in cases with either KRAS or BRAF mutant type. TCGA analysis showed a higher mRNA SLC2A1 expression in KRAS or BRAF-mutated tumours than in wild-type tumours (P = 0.02).

CONCLUSION

Our findings support the laboratory evidence for a potential benefit of vitamin C for CRC patients with KRAS or BRAF mutated tumours.

HER3- A key survival pathway and an emerging therapeutic target in metastatic colorectal cancer and pancreatic ductal adenocarcinoma

Colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDAC) are highly metastatic cancers with poor survival rates. The tumor microenvironment has been shown to play a critical role in cancer progression and response to therapies. Endothelial cells (ECs) are a key component of the tumor microenvironment and promote cancer cell survival by secreting soluble factors that activate cancer-promoting signaling pathways. Studies from us and others identified HER3 as a key mediator of liver EC-induced chemoresistance and cancer cell growth in metastatic CRC and PDAC. In this article, we discuss that HER3-targeted therapies may be effective in treating patients with HER3-expressing CRC and PDAC, and highlight the importance of applying HER3 expression as a predictive biomarker for patient response to HER3-targeted therapies. We also discuss the challenges encountered in past clinical trials of HER3-targeted therapies, including the role of NRG1 gene fusions, alternative HER3 activation mechanisms, and adaptive resistance mechanisms. Finally, we conclude by suggesting the future directions of HER3-targeted therapies, including novel approaches to overcome chemoresistance and promote cancer cell death.

The role of tumour biological factors in technical anatomical resectability assessment of colorectal liver metastases following induction systemic treatment: An analysis of the Dutch CAIRO5 trial

BACKGROUND

Large inter-surgeon variability exists in technical anatomical resectability assessment of colorectal cancer liver-only metastases (CRLM) following induction systemic therapy. We evaluated the role of tumour biological factors in predicting resectability and (early) recurrence after surgery for initially unresectable CRLM.

METHODS

482 patients with initially unresectable CRLM from the phase 3 CAIRO5 trial were selected, with two-monthly resectability assessments by a liver expert panel. If no consensus existed among panel surgeons (i.e. same vote for (un)resectability of CRLM), conclusion was based on majority. The association of tumour biological (sidedness, synchronous CRLM, carcinoembryonic antigen and RAS/BRAF^V600E mutation status) and technical anatomical factors with consensus among panel surgeons, secondary resectability and early recurrence (<6 months) without curative-intent repeat local treatment was analysed by uni- and pre-specified multivariable logistic regression.

RESULTS

After systemic treatment, 240 (50%) patients received complete local treatment of CRLM of which 75 (31%) patients experienced early recurrence without repeat local treatment. Higher number of CRLM (odds ratio 1.09 [95% confidence interval 1.03-1.15]) and age (odds ratio 1.03 [95% confidence interval 1.00-1.07]) were independently associated with early recurrence without repeat local treatment. In 138 (52%) patients, no consensus among panel surgeons was present prior to local treatment. Postoperative outcomes in patients with and without consensus were comparable.

CONCLUSIONS

Almost a third of patients selected by an expert panel for secondary CRLM surgery following induction systemic treatment experience an early recurrence only amenable to palliative treatment. Number of CRLM and age, but no tumour biological factors are predictive, suggesting that until there are better biomarkers; resectability assessment remains primarily a technical anatomical decision.

Mutations matter: An observational study of the prognostic and predictive value of KRAS mutations in metastatic colorectal cancer

BACKGROUND

About half of metastatic colorectal cancers (CRCs) harbor Rat Sarcoma (RAS) activating mutations as oncogenic driver, but the prognostic role of RAS mutations is not fully elucidated. Interestingly, specific hotspot mutations have been identified as potential candidates for novel targeted therapies in several malignancies as per G12C. This study aims at evaluating the association between KRAS hotspot mutations and patient characteristics, prognosis and response to antiangiogenic drugs.

METHODS

Data from RAS-mutated CRC patients referred to Careggi University Hospital, between January 2017 and April 2022 were retrospectively and prospectively collected. Tumor samples were assessed for RAS mutation status using MALDI-TOF Mass Spectrometry, Myriapod NGS-56G Onco Panel, or Myriapod NGS Cancer Panel DNA.

RESULTS

Among 1047 patients with available RAS mutational status, 183 KRAS-mutated patients with advanced CRC had adequate data for clinicopathological and survival analysis. KRAS mutations occurred at codon 12 in 67.2% of cases, codon 13 in 23.5%, codon 61 in 2.2%, and other codons in 8.2%. G12C mutation was identified in 7.1% of patients and exon 4 mutations in 7.1%. KRAS G12D mutation, as compared to other mutations, was significantly associated with liver metastases (1-sided p=0.005) and male sex (1-sided p=0.039), KRAS G12C mutation with peritoneal metastases (1-sided p=0.035), KRAS G12V mutation with female sex (1-sided p=0.025) and no surgery for primary tumor (1-sided p=0.005). No associations were observed between specific KRAS variants and age, ECOG PS, site of primary tumor, pattern of recurrence for resected patients, and lung, distant lymph node, bone, or brain metastases.Overall survival (OS) was significantly longer in patients with KRAS exon 4 mutations than in those with other KRAS mutations (mOS 43.6 months vs 20.6 months; HR 0.45 [0.21-0.99], p=0.04). No difference in survival was observed for mutations at codon 12/13/61 (p=0.1). Treatment with bevacizumab (BV) increased significatively mPFS (p=0.036) and mOS (p=0.019) of the entire population with a substantial benefit in mOS for G12V mutation (p=0.031).

CONCLUSIONS

Patterns of presentation and prognosis among patients with specific RAS hotspot mutations deserve to be extensively studied in large datasets, with a specific attention to the uncommon isoforms and the role of anti-angiogenic drugs.

Somatic mutations in colorectal cancer: regional experience

Introduction. Colorectal cancer is one of the most common malignant neoplasms in economically developed countries, ranking 3rd and 2nd in the structure of morbidity and mortality, respectively. Current knowledge about the molecular features of colorectal cancer is necessary to implement the principle of personalized therapy. Aim. To study regional features of tumor genomic landscape in colorectal cancer. Materials and methods. The retrospective study from 2019 to 2022 included 153 patients with stage IIV colorectal cancer aged 32 to 80 years, with a median of 63.8 years. DNA samples extracted from paraffin blocks of tumor tissue were analyzed using a real-time polymerase chain reaction. The study patients included 43.8% of males and 56.2% of females. Results. Somatic mutations were detected in 48.4% of patients. The maximum number of mutations was detected in the KRAS gene 60 (81%). The mutation rate was significantly higher in females versus males. KRAS mutations predominate in the colon compared to the rectum, accounting for 66.7 and 33.3%, respectively. In tumors of the right colon, these mutations were detected in 18.3% of cases, and in the left colon, 48.4%. NRAS mutations were found in 9.5% of cases, mainly in tumors of the left colon. BRAF mutations were diagnosed in 6 patients, 5 of them were women, and the tumors were localized in the right colon. The highest rate of KRAS mutations was observed in codons 12 and 13, accounting for 86.7% of cases. The G12V mutation occurred in the majority of patients (25%), followed by G12D (20%) and G12A (16.6%). Conclusion. Somatic mutations in RAS and BRAF genes in colorectal cancer were detected in 48.4% of patients in the Tambov region. Among them, there is a predominance of KRAS mutations 81% in females. KRAS oncogenic mutations are predictors of treatment response and prognosis.