A novel KIF5B-ALK variant in nonsmall cell lung cancer

BACKGROUND

The anaplastic lymphoma kinase (ALK) gene is involved frequently in chromosomal translocations, resulting in fusion genes with different partners found in various lymphoproliferative conditions. It was recently reported in nonsmall cell lung cancer (NSCLC) that the fusion protein encoded by echinoderm microtubule-associated protein-like 4-ALK (EML4-ALK) fusion gene conferred oncogenic properties. The objective of the current study was to identify other possible ALK fusion genes in NSCLC.

METHODS

Immunohistochemical analysis was used to screen for aberrant ALK expression in primary NSCLC. The authors used 5' rapid amplification of complementary DNA ends to screen for potential, novel 5' fusion partners of ALK other than EML4-ALK. Reverse transcriptase-polymerase chain reaction and fluorescence in situ hybridization analyses were used to confirm the identity of 5' fusion partners. The genomic breakpoint was verified using genomic sequencing. Overexpression of the novel ALK fusion gene and variants 3a and 3b of EML4-ALK was performed to assess downstream signaling and functional effects.

RESULTS

The authors identified a novel gene resulting from the fusion of kinesin family member 5B (KIF5B) exon 15 to ALK exon 20 in a primary lung adenocarcinoma. Western blot analysis of clinical tumor tissues revealed the expression of a protein whose size correlated with that of the predicted KIF5B-ALK. Overexpression of KIF5B-ALK in mammalian cells led to the activation of signal transducer and activator of transcription 3 and protein kinase B and to enhanced cell proliferation, migration, and invasion.

CONCLUSIONS

The discovery of the novel KIF5B-ALK variant further consolidated the role of aberrant ALK signaling in lung carcinogenesis.

Non-small cell lung cancer cells expressing CD44 are enriched for stem cell-like properties

BACKGROUND

The cancer stem cell theory hypothesizes that cancers are perpetuated by cancer stem cells (CSC) or tumor initiating cells (TIC) possessing self-renewal and other stem cell-like properties while differentiated non-stem/initiating cells have a finite life span. To investigate whether the hypothesis is applicable to lung cancer, identification of lung CSC and demonstration of these capacities is essential.

METHODOLOGY/PRINCIPAL FINDING

The expression profiles of five stem cell markers (CD34, CD44, CD133, BMI1 and OCT4) were screened by flow cytometry in 10 lung cancer cell lines. CD44 was further investigated by testing for in vitro and in vivo tumorigenecity. Formation of spheroid bodies and in vivo tumor initiation ability were demonstrated in CD44(+) cells of 4 cell lines. Serial in vivo tumor transplantability in nude mice was demonstrated using H1299 cell line. The primary xenografts initiated from CD44(+) cells consisted of mixed CD44(+) and CD44(-) cells in similar ratio as the parental H1299 cell line, supporting in vivo differentiation. Semi-quantitative Real-Time PCR (RT-PCR) showed that both freshly sorted CD44(+) and CD44(+) cells derived from CD44(+)-initiated tumors expressed the pluripotency genes OCT4/POU5F1, NANOG, SOX2. These stemness markers were not expressed by CD44(-) cells. Furthermore, freshly sorted CD44(+) cells were more resistant to cisplatin treatment with lower apoptosis levels than CD44(-) cells. Immunohistochemical analysis of 141 resected non-small cell lung cancers showed tumor cell expression of CD44 in 50.4% of tumors while no CD34, and CD133 expression was observed in tumor cells. CD44 expression was associated with squamous cell carcinoma but unexpectedly, a longer survival was observed in CD44-expressing adenocarcinomas.

CONCLUSION/SIGNIFICANCE

Overall, our results demonstrated that stem cell-like properties are enriched in CD44-expressing subpopulations of some lung cancer cell lines. Further investigation is required to clarify the role of CD44 in tumor cell renewal and cancer propagation in the in vivo environment.

Double EGFR mutants containing rare EGFR mutant types show reduced in vitro response to gefitinib compared with common activating missense mutations

Epidermal growth factor receptor (EGFR) mutations are common in lung adenocarcinomas, especially from nonsmoking women of Asian descent. We have previously shown EGFR mutations occur in >70% of lung adenocarcinoma from nonsmokers in our population with a complex mutational profile, including 13% of EGFR double mutations. In this study, we investigated the in vitro gefitinib response of four EGFR double mutants identified in untreated patients, including Q787R+L858R, E709A+G719C, T790M+L858R, and H870R+L858R. The phosphorylation profiles of EGFR and downstream effectors AKT, STAT3/5, and ERK1/2 were compared by immunoblot analyses among the single and double mutants transfected into H358 cells. Results showed that mutants responded to in vitro gefitinib treatment with different sensitivities. The G719C and L858R single mutants showed the highest gefitinib sensitivity compared with the corresponding coexisting single mutants E709A, Q787R, H870R, and T790M. The double mutants E709A+G719C, Q787R+L858R, and H870R+L858R showed attenuated responses to gefitinib in the EGFR and downstream effector phosphorylation profiles compared with G719C or L858R alone. T790M+L858R showed strong resistance to gefitinib. Clinically, the patient whose tumor contained H870R+L858R showed tumor stabilization by 250 mg oral gefitinib daily but cerebral metastasis developed 6 months later. Correlation with the in vitro phosphorylation profile of H870R+L858R suggested that treatment failure was probably due to inadequate suppression of EGFR signaling by the drug level attainable in the cerebrospinal fluid at the given oral dosage. Overall, the findings suggested that rare types of EGFR substitution mutations could confer relative gefitinib resistance when combined with the common activating mutants.

The EML4-ALK fusion gene is involved in various histologic types of lung cancers from nonsmokers with wild-type EGFR and KRAS

BACKGROUND

The echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) fusion gene resulting from the chromosome inversion inv(2)(p21;p23) recently was identified in nonsmall cell lung cancer (NSCLC). The authors of this study investigated the frequency, genetic and clinicopathologic profiles of EML4-ALK in Chinese patients with NSCLC.

METHODS

EML4-ALK was investigated in 266 resected primary NSCLC, including adenocarcinomas (AD), lymphoepithelioma-like carcinomas, squamous cell carcinomas, mucoepidermoid carcinomas, and adenosquamous carcinomas, by reverse transcriptase-polymerase chain reaction and was verified by sequencing. EML4-ALK protein expression was studied by immunohistochemistry.

RESULTS

Thirteen tumors (4.9%) had EML4-ALK comprising 4 fusion transcript variants with fusion of the variable segments from 5' EML4 to 3' ALK and with preservation of the ALK kinase domain. The most common variant consisted of 8 tumors with variant 3 that involved EML4 exon 6. The others included 2 tumors with variant 1 (exon 13), 2 tumors with variant 2 (exon 20), and 1 tumor with the novel variant 5 (exon 18). There were 11 ADs and 2 unusual carcinomas with mixed squamous and glandular components. Immunohistochemistry demonstrated diffuse ALK fusion proteins in the tumor cell cytoplasm. EML4-ALK was associated with nonsmokers (P = .009). Tumors with the fusion gene had the wild-type epidermal growth factor receptor (EGFR) (P = .001) and v-Ki-ras2/Kirsten rat sarcoma viral oncogene homolog (KRAS) genes. Patients who had EML4-ALK-positive AD had a younger median age (P = .018) compared with patients who did not have the fusion gene.

CONCLUSIONS

The EML4-ALK fusion gene was present in various histologic types of NSCLC. It occurred in mutual exclusion to EGFR and KRAS mutations and was associated with nonsmokers. The authors concluded that EML4-ALK may be useful for predicting the potential response to ALK inhibitors as a therapeutic option for patients with lung cancer.

SRC promotes survival and invasion of lung cancers with epidermal growth factor receptor abnormalities and is a potential candidate for molecular-targeted therapy

Molecular-targeted therapy using tyrosine kinase inhibitors against epidermal growth factor receptor (EGFR) is an effective therapy for non-small cell lung cancer that harbor EGFR mutations. This study aimed to investigate the role of Src, a close EGFR associator, as a drug target in NSCLC cells with different EGFR genomic statuses. Src inhibition was achieved using 4-(4'-Phenoxyanilino)-6,7-dimethoxyquinazolinee (SKI-1) and the specificity of action was verified by RNA interference. The results showed that SKI-1 induced significant apoptosis in a dose-dependent manner in cancer cells with high basal Src activation. Activation of FAK and p130Cas was involved in Src-mediated invasion in SKI-1-sensitive cells. SKI-1 inhibited phosphorylation of EGFR as well as EGFR downstream effectors, such as signal transducers and activators of transcription 3/5, extracellular signal-regulated kinase 1/2 and AKT in the mutant cells but not the wild-type cells. This inhibition profile of EGFR implicates that induction of apoptosis and sensitivity of mutant cells to SKI treatment is mediated by EGFR and EGFR downstream pathways. Cotreatment with SKI-1 and gefitinib enhanced apoptosis in cancer cells that contained EGFR mutation and/or amplification. SKI-1 treatment alone induced significant apoptosis in H1975 cells known to be resistant to gefitinib. Src phosphorylation was shown by immunohistochemistry in around 30% of primary lung carcinomas. In 152 adenocarcinomas studied, p-Src was associated with EGFR mutations (P = 0.029). Overall, the findings indicated that Src could be a useful target for treatment of non-small cell lung cancer. Besides EGFR genomic mutations, other forms of EGFR and related family member abnormalities such as EGFR amplification might enhance SKI sensitivity.

Video-assisted thoracic surgery for mediastinal extramedullary haematopoiesis

Extramedullary haematopoiesis is a rare cause of an intrathoracic mass. We report a case of posterior mediastinal extramedullary haematopoietic mass in a 50-year-old man who presented with non-specific symptoms and a paravertebral mass on chest X-ray. Diagnosis was achieved by using video-assisted thoracic surgery.