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A cross-sectional study examining the expression of splice variants K-RAS4A and K-RAS4B in advanced non-small-cell

Veronica Aran¹, Pedro Masson Domingues¹, Fabiane Carvalho de Macedo²

¹Clinical Research Division, Brazilian National Cancer Institute (INCA), Rio de Janeiro, Brazil.

Lung Cancer (Amsterdam, Netherlands)

|February 8, 2018

Abstract

Objectives:

Mammalian cells differently express 4 RAS isoforms: H-RAS, N-RAS, K-RAS4A and K-RAS4B, which are important in promoting oncogenic processes when mutated. In lung cancer, the K-RAS isoform is the most frequently altered RAS protein, being also a difficult therapeutic target. Interestingly, there are two K-RAS splice variants (K-RAS4A and K-RAS4B) and little is known about the role of K-RAS4A. Most studies targeting K-RAS, or analysing it as a prognostic factor, have not taken into account the two isoforms. Consequently, the in-depth investigation of them is needed.

Methods:

The present study analysed 98 specimens from advanced non-small cell lung cancer (NSCLC) adenocarcinoma patients originated from Brazil. The alterations present in K-RAS at the DNA level (Sanger sequencing) as well as the expression of the splicing isoforms at the RNA (qRT-PCR) and protein levels (immunohistochemistry analysis), were evaluated. Possible associations between clinicopathological features and the molecular findings were also investigated.

Results:

Our results showed that in the non-smoking population, the cancer incidence was higher among women. In contrast, in smokers and former smokers, the incidence was higher among men. Regarding sequencing results, 10.5% of valid samples presented mutations in exon 2, being all wild-type for exon 3, and the most frequently occurring base change was the transversion G → T. Our qRT-PCR and immunohistochemical analysis showed that both, K-RAS4A and K-RAS4B, were differently expressed in NSCLC tumour samples. For example, tumour specimens showed higher K-RAS4A mRNA expression in relation to commercial normal lung control than did K-RAS4B. In addition, K-RAS4B protein expression was frequently stronger than K-RAS4A in the patients analysed.

Conclusion:

Our results highlight the differential expression of K-RAS4A and K-RAS4B in advanced adenocarcinoma NSCLC patients and underline the need to further clarify the enigma behind their biological significance in various cancer types, including NSCLC.

Insights

This study investigated K-RAS4A and K-RAS4B expression in lung cancer, finding differential expression of these isoforms. Further research is needed to understand their biological significance in cancer.

Area of Science:

Oncology
Molecular Biology
Genetics

Background:

Mammalian cells express four RAS isoforms (H-RAS, N-RAS, K-RAS4A, K-RAS4B), with mutations promoting oncogenesis.
K-RAS is the most frequently altered RAS isoform in lung cancer and a challenging therapeutic target.
Little is known about the specific role of the K-RAS4A splice variant.

Purpose of the Study:

To investigate the differential expression of K-RAS4A and K-RAS4B isoforms in advanced non-small cell lung cancer (NSCLC) adenocarcinoma.
To analyze K-RAS DNA alterations and correlate them with clinicopathological features.
To explore the distinct roles of K-RAS4A and K-RAS4B in NSCLC.

Main Methods:

Analysis of 98 advanced NSCLC adenocarcinoma specimens from Brazil.
K-RAS DNA alterations assessed via Sanger sequencing.
K-RAS4A and K-RAS4B expression evaluated at RNA (qRT-PCR) and protein (immunohistochemistry) levels.

Main Results:

In non-smokers, cancer incidence was higher in women; in smokers, it was higher in men.
10.5% of samples had K-RAS mutations (exon 2), with G→T transversion being most common.
Both K-RAS4A and K-RAS4B showed differential expression in NSCLC tumors; K-RAS4A mRNA was higher, while K-RAS4B protein expression was often stronger.

Conclusions:

K-RAS4A and K-RAS4B exhibit distinct expression patterns in advanced NSCLC adenocarcinoma.
The biological significance of these differential expressions warrants further investigation across various cancer types.
Understanding isoform-specific roles is crucial for targeted therapies in lung cancer.

Read full analysis

Keywords:

Adenocarcinoma Cancer patients K-RAS4A K-RAS4B Non-small cell lung cancer Splice variants

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