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  • Author: Xiaozhong Liu x
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With the rapid growth of the smartphone and tablet market, mobile application (App) industry that provides a variety of functional devices is also growing at a striking speed. Product life cycle (PLC) theory, which has a long history, has been applied to a great number of industries and products and is widely used in the management domain. In this study, we apply classical PLC theory to mobile Apps on Apple smartphone and tablet devices (Apple App Store). Instead of trying to utilize often-unavailable sales or download volume data, we use open-access App daily download rankings as an indicator to characterize the normalized dynamic market popularity of an App. We also use this ranking information to generate an App life cycle model. By using this model, we compare paid and free Apps from 20 different categories. Our results show that Apps across various categories have different kinds of life cycles and exhibit various unique and unpredictable characteristics. Furthermore, as large-scale heterogeneous data (e.g., user App ratings, App hardware/software requirements, or App version updates) become available and are attached to each target App, an important contribution of this paper is that we perform in-depth studies to explore how such data correlate and affect the App life cycle. Using different regression techniques (i.e., logistic, ordinary least squares, and partial least squares), we built different models to investigate these relationships. The results indicate that some explicit and latent independent variables are more important than others for the characterization of App life cycle. In addition, we find that life cycle analysis for different App categories requires different tailored regression models, confirming that inner-category App life cycles are more predictable and comparable than App life cycles across different categories.


Background: The alternative splicing of Bcl-x generates the proapoptotic Bcl-xs protein and the antiapoptotic variant Bcl-xl. Previous studies have demonstrated that some chemotherapeutic agents such as emetine, staurosporine, and epigallocatechin gallate (EGCG) in combination with ibuprofen significantly altered the ratio of the Bcl-x variants Bcl-xs/Bcl-xl in various cell lines, suggesting Bcl-x splicing might be affected by the exogenous stimuli.

Objective: We investigated the regulative role of imatinib in the alternative pre-mRNA splicing of Bcl-x in K562 cells and the related mechanism.

Methods: Cell proliferation was measured using WST assay kit. Cell apoptosis was assayed using an Annexin V-FITC Apoptosis Detection Kit. RT-PCR and western blot assay was used to analyze the mRNA and protein level of alternative splicing of exon 2 in the Bcl-x gene respectively.

Results: Imatinib regulated the alternative splicing in the Bcl-x gene in the K562 cells. In addition, we found that hydroxyurea, another agent for the therapy of CML, could enhance the effect of imatinib on the ratio of the Bcl-xl/Bcl-xs. Moreover, the induction of alternative splicing was correlated with protein phosphatase 1 (PP1). Alternatively, pretreatment with calyculin efficiently blocked imatinib-induced alternative splcing in the K562 cells compared with okadaic acid, which showed an important role of PP1 in regulating imatinib-induced splicing.

Conclusion: Imatinib regulates the alternative splicing of Bcl-x in K562 cells, which may be associated with the activation of PP1.