CDK7 and CDK9 inhibition interferes with transcription, translation, and stemness, and induces cytotoxicity in GBM irrespective of temozolomide sensitivity.

BACKGROUND: Glioblastoma (GBM) is refractory to current treatment modalities while side effects of treatments result in neurotoxicity and cognitive impairment. Here we test the hypothesis that inhibiting CDK7 or CDK9 would effectively combat GBM with reduced neurotoxicity. METHODS: We examined the effect of a CDK7 inhibitor, THZ1, and multiple CDK9 inhibitors (SNS032, AZD4573, NVP2, and JSH150) on GBM cell lines, patient-derived temozolomide (TMZ)-resistant and responsive primary tumor cells and glioma stem cells (GSCs). Biochemical changes were assessed by western blotting, immunofluorescence, multispectral imaging, and RT-PCR. In vivo, efficacy was assessed in orthotopic and subcutaneous xenograft models. RESULTS: CDK7 and CDK9 inhibitors suppressed the viability of TMZ-responsive and resistant GBM cells and GSCs at low nanomolar concentrations, with limited cytotoxic effects in vivo. The inhibitors abrogated RNA Pol II and p70S6K phosphorylation and nascent protein synthesis. Furthermore, the self-renewal of GSCs was significantly reduced with a corresponding reduction in Sox2 and Sox9 levels. Analysis of TCGA data showed increased expression of CDK7, CDK9, SOX2, SOX9, and RPS6KB1 in GBM; supporting this, multispectral imaging of a TMA revealed increased levels of CDK9, Sox2, Sox9, phospho-S6, and phospho-p70S6K in GBM compared to normal brains. RNA-Seq results suggested that inhibitors suppressed tumor-promoting genes while inducing tumor-suppressive genes. Furthermore, the studies conducted on subcutaneous and orthotopic GBM tumor xenograft models showed that administration of CDK9 inhibitors markedly suppressed tumor growth in vivo. CONCLUSIONS: Our results suggest that CDK7 and CDK9 targeted therapies may be effective against TMZ-sensitive and resistant GBM.

Reading difficulties in amblyopia: Consequence of visual sensory and oculomotor dysfunction.

INTRODUCTION: Reading is a vision-reliant task, requiring sequential eye movements. Binocularly discordant input results in visual sensory and oculomotor dysfunction in amblyopia, which may contribute to reading difficulties. This study aims to determine the contributions of fixation eye movement (FEM) abnormalities, clinical type and severity of amblyopia to reading performance under binocular and monocular viewing conditions. METHODS: Twenty-three amblyopic patients and nine healthy controls were recruited. Eye movements elicited during fixation and reading of preselected passages were collected for each subject using infrared video-oculography. Subjects were classified as having no nystagmus (n = 9), fusion maldevelopment nystagmus (FMN, n = 5), or nystagmus without structural anomalies that does not meet criteria for FMN or infantile nystagmus (n = 9). Reading rate (words/min), the number of forward and regressive saccades (per 100 words) and fixation duration (s) were computed. RESULTS: Amblyopic patients with and without nystagmus exhibited greater vergence and fixation instability. In patients without nystagmus, the instability arises from increased amplitude and velocity of fast and slow FEMs respectively. Amblyopic patients with and without nystagmus exhibited lower reading speeds with increased fixation duration, regressive and progressive saccades than controls in all viewing conditions. Mixed etiology, greater amblyopic eye visual acuity and stereopsis deficits were associated with greater reading difficulties under binocular viewing. CONCLUSIONS: The presence of oculomotor dysfunction and the extent of visual acuity and stereoacuity deficits contribute to reading difficulties in patients with amblyopia, with and without nystagmus. The understanding of reading difficulties is essential to devise accommodations to limit long-term academic and vocational consequences of amblyopia.