[Paraneoplastic neurologic syndromes. Diagnostic and pathogenetic significance of autoantibodies]

The small cell lung cancer-specific isoform of RE1-silencing transcription factor (REST) is regulated by neural-specific Ser/Arg repeat-related protein of 100 kDa (nSR100)

Small cell lung cancer (SCLC) is a highly malignant form of cancer, which originates from primitive neuroendocrine cells in the lung. SCLC cells express several autocrine neurotransmitters/neuropeptides and their respective receptors. Expression of these neuronal markers is frequently regulated by RE1-silencing transcription factor (REST). In SCLC cells, an SCLC-specific isoform of REST (sREST) is highly expressed, whereas REST expression is undetectable, suggesting that the expression of sREST correlates with the pathogenesis of SCLC. Expression of sREST, which is derived through alternative splicing of REST, is abnormally regulated in SCLC cells, but the mechanism is unknown. Most recently, nSR100 (SRRM4) was described as an activator of REST alternative splicing. We now show that nSR100 is highly expressed in SCLC cells correlating with high sREST and low REST expression. Adhesion to the extracellular matrix (ECM) is thought to enhance tumorigenicity and confer resistance to apoptosis. Interestingly, nSR100 expression is enhanced in cells grown with ECM. Overexpression of REST caused repression of sREST and nSR100, the latter containing RE1 element controlled by REST. Culturing the SCLC cell line NCI-N417 cells with ECM also upregulated RE1-containing gene, the voltage-gated calcium channel subunit. Inhibition of the PI3K/Akt/mTOR pathway by LY294002 induced nSR100 expression, whereas the specific MEK/ERK inhibitor U0126 inhibited nSR100 expression. Repressing nSR100 by siRNA effectively repressed sREST, and conversely increased REST in NCI-N417 cells. Taken together, this report clarifies the ECM-dependent signaling pathway that impacts nSR100 expression and its regulation of alternative splicing in SCLC.

IMPLICATIONS

The splicing factor nSR100 may be novel SCLC-specific biomarker, as well as a therapeutic target.

[Small cell lung cancer and cancer-associated retinopathy]

We report the case of a patient who presented with cancer-associated retinopathy and small cell carcinoma of the lung, which was treated surgically because the initial diagnostic biopsy finding was squamous cell carcinoma. The patient then underwent chemotherapy and radiation therapy. We discuss the characteristics and pathogenesis of this paraneoplastic syndrome as well as its association with the lung tumor's aberrant production of a protein that competes with retinal recoverin at the photoreceptors of the retinal cone.

Relaxation of glycine receptor and onconeural gene transcription control in NRSF deficient small cell lung cancer cell lines

Negative regulation of many neuronal genes is mediated by the neuron-restrictive silencer factor (NRSF/repressor element-1 binding transcription factor, REST), which binds to the neuron-restrictive silencer element (NRSE/repressor element-1, RE-1) and thereby represses transcription of neuronal genes in non-neuronal cells. Sequence analysis of 5'-flanking regions of glycine receptor (GlyR) subunit genes revealed a consensus motif for NRSE in the GLRA1 and GLRA3, but not in GLRB, genes. In this study, we examined tumor cell lines for the expression of NRSF, GlyR subunits and onconeural genes. We identified two small cell lung cancer (SCLC) cell lines lacking full-length NRSF/REST as well as its neuronal splice variants. Presence or absence of NRSF as well as its functionality in different SCLC cell lines was additionally shown in reporter gene assays. As GlyR alpha1 is selectively transcribed in NRSF/REST free cells, GlyR alpha1 transcripts might serve as positive signals for NRSF deficient cells. In contrast, GlyR beta is nearly ubiquitously transcribed in the cell lines analyzed and, therefore, should represent a useful marker for neoplastic cells. Sequence analysis of GlyR beta transcripts led to the identification of a new splice variant lacking exon 8, GlyR beta Delta8. This suggests that the lack of NRSF in SCLC cells, resulting in the relaxation of neuronal gene suppression, is an important mechanism underlying paraneoplastic expression.

Paraneoplastic neurological syndromes - patients' cohort profile in the Czech Republic

Reported paraneoplastic neurological syndromes (PNS) are rare disabling neurological diseases with supposed autoimmune pathogenesis. The aims of this study were to evaluate frequency, clinical course and therapeutic response in the cohort of PNS positive patients (n=10) in the Czech Republic for the first time. Second, we determined the presence and distribution of oligoclonal IgG bands (OB IgG) in PNS and compared the clinical and laboratory features of OB IgG positive and negative patients. A total of 2355 suspicious serum and/or CSF samples were screened by immunofluorescence and immunohistochemistry with definite confirmation by Western blot. OB IgG were detected by isoelectric focusing and immunoenzymatic staining and clinical status was scored according to modified Rankin scale (RS). Four patients had anti-Yo antibody, ovarian cancer and the score in range (2-5) on RS. Five patients had anti-Hu antibody, small cell lung cancer (SCLC), prostate cancer and the score between 1-4 grade on RS. One patient with SCLC and anti-Ri antibody had grade 2. Five of 10 patients with PNS had positive OB IgG and average value 4.2 on RS comparing with negative OB IgG patients with average value 2.6. Finally, we add well-defined cohort of PNS patients to emerging European profile of PNS and conclude that the presence of OB IgG in PNS seems to reflect enhanced immune response with more severe neurological damage and clinical course.