Cellular growth, development, and differentiation are tightly controlled by a conserved biological mechanism: the cell cycle. This cycle is primarily regulated by cyclin-dependent kinase (CDK)-cyclin complexes, checkpoint kinases, and CDK inhibitors. Deregulation of the cell cycle is a hallmark of the transformation of normal cells into tumor cells. Given its importance in tumorigenesis, several cell cycle inhibitors have emerged as potential therapeutic drugs for the treatment of cancers-both as single-agent therapy and in combination with traditional cytotoxic or molecular targeting agents. In this review, we discuss the mechanisms underlying cell cycle regulation and present small-molecule anticancer drugs that are under development, including both pan-CDK inhibitors and CDK4/6-selective inhibitors. In addition, we provide an outline of some promising CDK inhibitors currently in preclinical and clinical trials that target cell cycle abnormalities in various cancers.

The transfer of genetic material from the mitochondria and plastid to the nucleus gives rise to nuclear integrants of mitochondrial DNA (NUMTs) and nuclear integrants of plastid DNA (NUPTs). This frequently occurring DNA transfer is ongoing and has important evolutionary implications. In this review, based on previous studies and the analysis of NUMT/NUPT insertions of more than 200 sequenced plant genomes, we analyzed and summarized the general features of NUMTs/NUPTs and highlighted the genetic consequence of organellar DNA insertions. The statistics of organellar DNA integrants among various plant genomes revealed that organellar DNA-derived sequence content is positively correlated with the nuclear genome size. After integration, the nuclear organellar DNA could undergo different fates, including elimination, mutation, rearrangement, fragmentation, and proliferation. The integrated organellar DNAs play important roles in increasing genetic diversity, promoting gene and genome evolution, and are involved in sex chromosome evolution in dioecious plants. The integrating mechanisms, involving non-homologous end joining at double-strand breaks were also discussed.

Background: This study investigated the mechanism of drug resistance in non-small cell lung cancer (NSCLC) patients. We specifically studied whether long noncoding RNAs influence drug resistance in NSCLC to discover new therapeutic targets to increase the survival rate of drug-resistant NSCLC patients. Methods: Tissue samples were collected from NSCLC patients, and total RNA was isolated for assessment of HOTAIR expression and drug resistance status. MTT assays, tumor sphere formation assays, and western blot were performed to cytologically determine the relationship between HOTAIR expression and cisplatin resistance, as well as to elucidate the potential molecular mechanism involved. Results: HOTAIR expression in tissues of drug-resistant NSCLC patients was higher than that of nondrug-resistant patients. HOTAIR expression was elevated in cisplatin-resistant cell strains (A549/CDDP), and reducing HOTAIR expression increased the sensitivity of A549/CDDP cells to cisplatin. In addition, overexpression of HOTAIR in A549 cells increased resistance to cisplatin. Tumor sphere formation assays showed that the volume of spheres formed by cell strains expressing elevated levels of HOTAIR was greater than that of cell strains with low expression. Western blot experiments showed that elevated expression of HOTAIR upregulated tumor stem cell-related biomarkers and HOTAIR expression was directly related to Klf4 expression.Conclusions: Elevated HOTAIR expression is associated with drug resistance in NSCLC patients and is related to Klf4 upregulation, providing a new therapeutic target for drug-resistant NSCLC patients.