Clinical outcomes of ALK+ non-small cell lung cancer in Denmark

BACKGROUND

Real-world clinical outcomes of anaplastic lymphoma kinase positive (ALK+) non-small cell lung cancer (NSCLC) patients vary. This study aimed to investigate the treatment and clinical outcomes of all ALK+ NSCLC patients in Denmark in the period 2011-2018, regardless of disease stage.

MATERIALS AND METHODS

A national pathology database with complete coverage was used to identify ALK+ NSCLC patients diagnosed between 2011 and 2018. Clinical data were obtained through retrospective chart reviews. Overall survival (OS) and duration of treatment (DOT) were analyzed using Kaplan-Meier methodologies.

RESULTS

A total of 209 ALK+ NSCLC patients were included. The cohort had a slight overrepresentation of female patients (56.5%) with a mean age of 61.6 years. Most patients were adenocarcinoma cases (97%) and presented with an ECOG performance status of 0-1 (79%). Stage IIIb-IVb patients comprised 70% of the cohort. The use of ALK-tyrosine kinase inhibitors (TKIs) as first-line treatment increased over time, with the 1st generation ALK-TKI crizotinib being the predominant treatment in the 1st line. In 1st line treatment, 2nd generation ALK-TKIs had a median DOT more than twice the median DOT of crizotinib (25.1 and 9.1 months, respectively). The median OS for the entire cohort was 44.0 months. Patients with stage I-IIIA disease had a median OS that had not been reached, while those with stage IIIb-IVb disease had a median OS of 31.8 months. Patients with stage IIIb-IVb disease receiving an ALK-TKI as 1st line treatment had a median OS of 42.5 months with immature follow-up. Brain metastases at diagnosis or choice of 1st line treatment did not statistically significantly impact OS.

CONCLUSION

This study gives insights into the treatment and outcome of ALK+ NSCLC patients in Denmark and provides a real-world confirmation of the superior disease control provided by 2nd generation ALK-TKIs as compared to the 1st generation ALK-TKI crizotinib.

The tumor suppressor folliculin regulates AMPK-dependent metabolic transformation

The Warburg effect is a tumorigenic metabolic adaptation process characterized by augmented aerobic glycolysis, which enhances cellular bioenergetics. In normal cells, energy homeostasis is controlled by AMPK; however, its role in cancer is not understood, as both AMPK-dependent tumor-promoting and -inhibiting functions were reported. Upon stress, energy levels are maintained by increased mitochondrial biogenesis and glycolysis, controlled by transcriptional coactivator PGC-1α and HIF, respectively. In normoxia, AMPK induces PGC-1α, but how HIF is activated is unclear. Germline mutations in the gene encoding the tumor suppressor folliculin (FLCN) lead to Birt-Hogg-Dubé (BHD) syndrome, which is associated with an increased cancer risk. FLCN was identified as an AMPK binding partner, and we evaluated its role with respect to AMPK-dependent energy functions. We revealed that loss of FLCN constitutively activates AMPK, resulting in PGC-1α-mediated mitochondrial biogenesis and increased ROS production. ROS induced HIF transcriptional activity and drove Warburg metabolic reprogramming, coupling AMPK-dependent mitochondrial biogenesis to HIF-dependent metabolic changes. This reprogramming stimulated cellular bioenergetics and conferred a HIF-dependent tumorigenic advantage in FLCN-negative cancer cells. Moreover, this pathway is conserved in a BHD-derived tumor. These results indicate that FLCN inhibits tumorigenesis by preventing AMPK-dependent HIF activation and the subsequent Warburg metabolic transformation.

Absence of the Birt-Hogg-Dubé gene product is associated with increased hypoxia-inducible factor transcriptional activity and a loss of metabolic flexibility

Under conditions of reduced tissue oxygenation, hypoxia-inducible factor (HIF) controls many processes, including angiogenesis and cellular metabolism, and also influences cell proliferation and survival decisions. HIF is centrally involved in tumour growth in inherited diseases that give rise to renal cell carcinoma (RCC), such as Von Hippel-Lindau syndrome and tuberous sclerosis complex. In this study, we examined whether HIF is involved in tumour formation of RCC in Birt-Hogg-Dubé syndrome. For this, we analysed a Birt-Hogg-Dubé patient-derived renal tumour cell line (UOK257) that is devoid of the Birt-Hogg-Dubé protein (BHD) and observed high levels of HIF activity. Knockdown of BHD expression also caused a threefold activation of HIF, which was not as a consequence of more HIF1α or HIF2α protein. Transcription of HIF target genes VEGF, BNIP3 and CCND1 was also increased. We found nuclear localization of HIF1α and increased expression of VEGF, BNIP3 and GLUT1 in a chromophobe carcinoma from a Birt-Hogg-Dubé patient. Our data also reveal that UOK257 cells have high lactate dehydrogenase, pyruvate kinase and 3-hydroxyacyl-CoA dehydrogenase activity. We observed increased expression of pyruvate dehydrogenase kinase 1 (a HIF gene target), which in turn leads to increased phosphorylation and inhibition of pyruvate dehydrogenase. Together with increased protein levels of GLUT1, our data reveal that UOK257 cells favour glycolytic rather than lipid metabolism (a cancer phenomenon termed the 'Warburg effect'). UOK257 cells also possessed a higher expression level of the L-lactate influx monocarboxylate transporter 1 and consequently utilized L-lactate as a metabolic fuel. As a result of their higher dependency on glycolysis, we were able to selectively inhibit the growth of these UOK257 cells by treatment with 2-deoxyglucose. This work suggests that targeting glycolytic metabolism may be used therapeutically to treat Birt-Hogg-Dubé-associated renal lesions.

Renal tumour suppressor function of the Birt-Hogg-Dubé syndrome gene product folliculin

BACKGROUND

Renal cell carcinoma (RCC) comprises five major molecular and histological subtypes. The Birt-Hogg-Dubé (BHD) syndrome is a hereditary human cancer syndrome that predisposes affected individuals to develop renal carcinoma of nearly all subtypes, in addition to benign fibrofolliculomas, and pulmonary and renal cysts. BHD is caused by loss-of-function mutations in the folliculin (FLCN) protein. The molecular function of FLCN is still largely unknown; opposite and conflicting evidence of the role of FLCN in mammalian target of rapamycin signalling/phosphorylated ribosomal protein S6 (p-S6) activation had recently been reported.

RESULTS AND METHODS

Here, the expression pattern of murine Flcn was described, and it was observed that homozygous disruption of Flcn results in embryonic lethality early during development. Importantly, heterozygous animals manifest early preneoplastic kidney lesions, devoid of Flcn expression, that progress towards malignancy, including cystopapillary adenomas. A bona fide tumour suppressor activity of FLCN was confirmed by nude mouse xenograft assays of two human RCC cell lines with either diminished or re-expressed FLCN. It was observed that loss of FLCN expression leads to context-dependent effects on S6 activation. Indeed, solid tumours and normal kidneys show decreased p-S6 upon diminished FLCN expression. Conversely, p-S6 is found to be elevated or absent in FLCN-negative renal cysts.

CONCLUSION

In accordance with clinical data showing distinct renal malignancies arising in BHD patients, in this study FLCN is shown as a general tumour suppressor in the kidney.

Normalizing genes for quantitative RT-PCR in differentiating human intestinal epithelial cells and adenocarcinomas of the colon

As for other mRNA measurement methods, quantitative RT-PCR results need to be normalized relative to stably expressed genes. Widely used normalizing genes include beta-actin and glyceraldehyde-3-phosphate dehydrogenase. It has, however, become clear that these and other normalizing genes can display modulated patterns of expression across tissue types and during complex cellular processes such as cell differentiation and cancer progression. Our objective was to set the basis for identifying normalizing genes that displayed stable expression during enterocytic differentiation and between healthy tissue and adenocarcinomas of the human colon. We thus identified novel potential normalizing genes using previously generated cDNA microarray data and examined the alterations of expression of two of these genes as well as seven commonly used normalizing genes during the enterocytic differentiation process and between matched pairs of resection margins and primary carcinomas of the human colon using real-time RT-PCR. We found that ribosomal phosphoprotein P0 was particularly stable in all intestinal epithelial cell extracts, thereby representing a particularly robust housekeeping reference gene for the assessment of gene expression during the human enterocytic differentiation process. On the other hand, beta-2-microglobulin generated the best score as a normalizing gene for comparing human colon primary carcinomas with their corresponding normal mucosa of the resection margin, although others were found to represent acceptable alternatives. In conclusion, we identified and characterized specific normalizing genes that should significantly improve quantitative mRNA studies related to both the differentiation process of the human intestinal epithelium and adenocarcinomas of the human colon. This approach should also be useful to validate normalizing genes in other intestinal contexts.

Upregulation of a functional form of the beta4 integrin subunit in colorectal cancers correlates with c-Myc expression

The integrin beta4 subunit has been shown to be involved in various aspects of cancer progression. The aim of the present work was to evaluate the expression of beta4 in primary colon cancers and to investigate the occurrence of a previously identified intestinal nonfunctional variant of beta4 (beta4ctd-) for adhesion to laminin. Immunodetection of beta4 using a panel of antibodies and RT-PCR analyses were performed on series of paired primary colon tumors and corresponding resection margins. The beta4 subunit was found to be significantly overexpressed in cancer specimens at both the protein and transcript levels. Surprisingly, beta4 levels of expression were closely correlated with those of the oncogene c-Myc in individual specimens. In vitro studies of c-Myc overexpression showed an upregulation of beta4 promoter activity. Finally, the beta4ctd- form was identified in the normal proliferative colonic cells but was found to be predominantly absent in colon cancer cells, both in situ and in vitro. We concluded that the beta4ctd- form is lost from colon cancer cells, while the level of the wild-type form of beta4, which is functional for adhesion to laminin, is increased in primary tumors in relation with the expression of c-Myc.

Human intestinal epithelial cell survival and anoikis. Differentiation state-distinct regulation and roles of protein kinase B/Akt isoforms

We have shown previously that human intestinal epithelial cell survival and anoikis are distinctively regulated according to the state of differentiation. Here we analyzed the roles of protein kinase B/Akt isoforms in such differentiation state distinctions. Anoikis was induced in undifferentiated and differentiated enterocytes by inhibition of focal adhesion kinase (Fak; pharmacologic inhibition or overexpression of dominant-negative mutants) or beta1 integrins (antibody blocking) or by maintaining cells in suspension. Expression/activation parameters of Akt isoforms (Akt-1, Akt-2, and Akt-3) and Fak were analyzed. Activity of Akt isoforms was also blocked by inhibition of phosphatidylinositol 3-kinase or by overexpression of dominant-negative mutants. Here we report the following. 1) The expression/activation levels of Akt-1 increase overall during enterocytic differentiation, and those of Akt-2 decrease, whereas Akt-3 is not expressed. 2) Akt-1 activation is dependent on beta1 integrins/Fak signaling, regardless of the differentiation state. 3) Akt-2 activation is dependent on beta1 integrins/Fak signaling in undifferentiated cells only. 4) Activation of Akt-1 is phosphatidylinositol 3-kinase-dependent, whereas that of Akt-2 is not. 5) Akt-2 does not promote survival or apoptosis/anoikis. 6) Akt-1 is essential for survival. 7) Akt-2 cannot substitute for Akt-1 in the suppression of anoikis. Hence, the expression and regulation of Akt isoforms show differentiation state-specific distinctions that ultimately reflect upon their selective implication in the mediation of human intestinal epithelial cell survival. These data provide new insights into the synchronized regulation of cell survival/death that is required in the dynamic renewal process of tissues such as the intestinal epithelium.

Differentiation state-selective roles of p38 isoforms in human intestinal epithelial cell anoikis

BACKGROUND & AIMS

Little is known of the signaling events implicated in the induction of human enterocytic anoikis. In the present study, we analyzed the role of the stress-activated protein kinase p38 in this process.

METHODS

Anoikis was induced in undifferentiated and differentiated enterocytes by inhibition of focal adhesion kinase (Fak; pharmacologic inhibition or overexpression of a dominant negative form) or beta1 integrins (antibody blocking), or by maintaining cells in suspension. Expression/activation parameters of p38 (isoforms alpha, beta, gamma, delta) and of the Fak/phosphatidylinositol-3-kinase (PI3-K)/Akt anoikis-suppressing pathways were analyzed. Kinase activities of p38 isoforms also were blocked by pharmacologic inhibitors or by overexpression of dominant-negative forms.

RESULTS

(1) p38 activation is sustained transiently after induction of anoikis in both undifferentiated and differentiated enterocytes; (2) such sustenance of p38 activation is associated with a down-regulation of the Fak/PI3-K/Akt pathway; (3) distinct profiles of p38 isoform expression are exhibited by undifferentiated (alpha, beta, gamma) and differentiated (alpha, gamma, delta) enterocytes; (4) none of the 4 known p38 isoforms was found to promote cell survival in either differentiation state; and (5) only p38beta and p38delta are required specifically for anoikis in undifferentiated and differentiated cells, respectively.

CONCLUSIONS

Distinct p38 isoforms play a major role in the induction of enterocytic anoikis and the regulation of such selective p38 isoform-mediated anoikis is linked with the state of cell differentiation. These data provide novel insights into the synchronized regulation of cell survival/death required in the epithelial renewal process along the human intestinal crypt-villus axis.