Mutually Exclusive Cyclin-Dependent Kinase 4/Cyclin D1 and Cyclin-Dependent Kinase 6/Cyclin D2 Pairing Inactivates Retinoblastoma Protein and Promotes Cell Cycle Dysregulation in Multiple Myeloma

AMPK regulates immature boar Sertoli cell proliferation through affecting CDK4/Cyclin D3 pathway and mitochondrial function

Sertoli cell (SC) proliferation plays an important role in sperm production and quality; however, the regulatory mechanism of SC proliferation is not well understood. This study investigated the role of adenosine monophosphate-activated protein kinase (AMPK) in the regulation of immature boar SC activity. Cell counting kit-8, Seahorse XFe96, mitochondrial respiratory enzyme-related assay kits, and transmission electron microscopy were used to detect SC proliferative viability, oxygen consumption rate (OCR), mitochondrial respiratory enzyme activity, and the ultrastructure of primary cultured SCs in vitro from the testes of 21-day-old boars. A dual luciferase reporter assay was performed to determine the miRNA-mRNA target interaction. Western blotting was used to analyze cell proliferation-related protein expression of p38, p21, proliferating cell nuclear antigen (PCNA), Cyclin-dependent kinase 4 (CDK4), Cyclin D3, and phosphorylated retinoblastoma protein (Rb). Each experiment had a completely randomized design, with three replicates in each experiment. The results showed that the AMPK inhibitor (Compound C, 20 μM-24 h) increased cell proliferation viability, ATP production, and maximal respiration of SCs by 0.64-, 0.12-, and 0.08-fold (p < 0.05), respectively; increased the SC protein expression of PCNA, CDK4, Cyclin D3, and p-Rb by 0.13-, 0.09-, 0.88-, and 0.12-fold (p < 0.05), respectively; and decreased the SC protein expression of p38 and p21 by 0.36- and 0.27-fold (p < 0.05), respectively. The AMPK agonist AICAR (2 mM-6 h) significantly inhibited SC ultrastructure, OCR, mitochondrial respiratory enzyme activity, and cell proliferation-related protein levels. AMPK was validated to be a target gene of miR-1285 based on the result in which the miR-1285 mimic inhibited the luciferase activity of wild-type AMPK by 0.54-fold (p < 0.001). MiR-1285 mimic promoted the OCR of SCs, with 0.45-, 0.15-, 0.21-, and 0.30-fold (p < 0.01) increases in ATP production, basal and maximal respiration, and spare capacity, respectively. MiR-1285 mimic increased the mitochondrial respiratory enzyme activity of SCs, with 0.63-, 0.70-, and 0.97-fold (p < 0.01) increases in NADH-Q oxidoreductase, cytochrome c oxidase, and ATP synthase, respectively. Moreover, the miR-1285 mimic increased the protein expression of PCNA, CDK4, Cyclin D3, and p-Rb by 0.24-, 0.30-, 0.22-, and 0.13-fold (p < 0.05), respectively, and reduced the protein expression of p38 and p21 by 0.58- and 0.66-fold (p < 0.001). MiR-1285 inhibitor showed opposite effects on the above indicators and induced numerous autophagosomes and large lipid droplets in SCs. A high dose of estradiol (10 μM-6 h, showed a promotion of AMPK activation in a previous study) significantly inhibited SC ultrastructure, mitochondrial function, and proliferation-related pathways, while these adverse effects were weakened by Compound C treatment or miR-1285 mimic transfection. Our findings suggest that the activation and inhibition of AMPK induced by specific drugs or synthesized targeted miRNA fragments could regulate immature boar SC proliferative activity by influencing the CDK4/Cyclin D3 pathway and mitochondrial function; this helps to provide a basis for the prevention and treatment of male sterility in clinical practice.

Research strategies of small molecules as chemotherapeutics to overcome multiple myeloma resistance

Multiple myeloma (MM), a cancer of plasma cells, is the second most common hematological malignancy which is characterized by aberrant plasma cells infiltration in the bone marrow and complex heterogeneous cytogenetic abnormalities. Over the past two decades, novel treatment strategies such as proteasome inhibitors, immunomodulators, and monoclonal antibodies have significantly improved the relative survival rate of MM patients. However, the development of drug resistance results in the majority of MM patients suffering from relapse, limited treatment options and uncontrolled disease progression after relapse. There are urgent needs to develop and explore novel MM treatment strategies to overcome drug resistance and improve efficacy. Here, we review the recent small molecule therapeutic strategies for MM, and introduce potential new targets and corresponding modulators in detail. In addition, this paper also summarizes the progress of multi-target inhibitor therapy and protein degradation technology in the treatment of MM.

Multi-dimensional scaling techniques unveiled gain1q&loss13q co-occurrence in Multiple Myeloma patients with specific genomic, transcriptional and adverse clinical features

The complexity of Multiple Myeloma (MM) is driven by several genomic aberrations, interacting with disease-related and/or -unrelated factors and conditioning patients' clinical outcome. Patient's prognosis is hardly predictable, as commonly employed MM risk models do not precisely partition high- from low-risk patients, preventing the reliable recognition of early relapsing/refractory patients. By a dimensionality reduction approach, here we dissect the genomic landscape of a large cohort of newly diagnosed MM patients, modelling all the possible interactions between any MM chromosomal alterations. We highlight the presence of a distinguished cluster of patients in the low-dimensionality space, with unfavorable clinical behavior, whose biology was driven by the co-occurrence of chromosomes 1q CN gain and 13 CN loss. Presence or absence of these alterations define MM patients overexpressing either CCND2 or CCND1, fostering the implementation of biology-based patients' classification models to describe the different MM clinical behaviors.

CDK6 protein expression is associated with disease progression and treatment resistance in multiple myeloma

Multiple myeloma (MM) is a heterogeneous malignancy of plasma cells. Despite improvement in the prognosis of MM patients after the introduction of many new drugs in the past decades, MM remains incurable since most patients become treatment-resistant. Cyclin-dependent kinase 6 (CDK6) is activated in many types of cancer and has been associated with drug resistance in MM. However, its association with disease stage, genetic alterations, and outcome has not been systematically investigated in large cohorts. Here, we analyzed CDK6 expression using immunohistochemistry in 203 formalin-fixed paraffin-embedded samples of 146 patients and four healthy individuals. We found that 61.5% of all MM specimens express CDK6 at various levels. CDK6 expression increased with the progression of disease with a median of 0% of CDK6-positive plasma cells in monoclonal gammopathy of undetermined significance (MGUS) (n = 10) to 30% in newly diagnosed MM (n = 78) and up to 70% in relapsed cases (n = 55). The highest median CDK6 was observed in extramedullary myeloma (n = 12), a highly aggressive manifestation of MM. Longitudinal analyses revealed that CDK6 is significantly increased in lenalidomide-treated patients but not in those who did not receive lenalidomide. Furthermore, we observed that patients who underwent lenalidomide-comprising induction therapy had significantly shorter progression-free survival when their samples were CDK6 positive. These data support that CDK6 protein expression is a marker for aggressive and drug-resistant disease and describes a potential drug target in MM.

Inhibition of VCP modulates NF-κB signaling pathway to suppress multiple myeloma cell proliferation and osteoclast differentiation

Multiple myeloma (MM) is the second most common hematological malignancy, in which the dysfunction of the ubiquitin-proteasome pathway is associated with the pathogenesis. The valosin containing protein (VCP)/p97, a member of the AAA+ ATPase family, possesses multiple functions to regulate the protein quality control including ubiquitin-proteasome system and molecular chaperone. VCP is involved in the occurrence and development of various tumors while still elusive in MM. VCP inhibitors have gradually shown great potential for cancer treatment. This study aims to identify if VCP is a therapeutic target in MM and confirm the effect of a novel inhibitor of VCP (VCP20) on MM. We found that VCP was elevated in MM patients and correlated with shorter survival in clinical TT2 cohort. Silencing VCP using siRNA resulted in decreased MM cell proliferation via NF-κB signaling pathway. VCP20 evidently inhibited MM cell proliferation and osteoclast differentiation. Moreover, exosomes containing VCP derived from MM cells partially alleviated the inhibitory effect of VCP20 on cell proliferation and osteoclast differentiation. Mechanism study revealed that VCP20 inactivated the NF-κB signaling pathway by inhibiting ubiquitination degradation of IκBα. Furthermore, VCP20 suppressed MM cell proliferation, prolonged the survival of MM model mice and improved bone destruction in vivo. Collectively, our findings suggest that VCP is a novel target in MM progression. Targeting VCP with VCP20 suppresses malignancy progression of MM via inhibition of NF-κB signaling pathway.

Proteomic profiling reveals CDK6 upregulation as a targetable resistance mechanism for lenalidomide in multiple myeloma

The immunomodulatory drugs (IMiDs) lenalidomide and pomalidomide are highly effective treatments for multiple myeloma. However, virtually all patients eventually relapse due to acquired drug resistance with resistance-causing genetic alterations being found only in a small subset of cases. To identify non-genetic mechanisms of drug resistance, we here perform integrated global quantitative tandem mass tag (TMT)-based proteomic and phosphoproteomic analyses and RNA sequencing in five paired pre-treatment and relapse samples from multiple myeloma patients. These analyses reveal a CDK6-governed protein resistance signature that includes myeloma high-risk factors such as TRIP13 and RRM1. Overexpression of CDK6 in multiple myeloma cell lines reduces sensitivity to IMiDs while CDK6 inhibition by palbociclib or CDK6 degradation by proteolysis targeting chimeras (PROTACs) is highly synergistic with IMiDs in vitro and in vivo. This work identifies CDK6 upregulation as a druggable target in IMiD-resistant multiple myeloma and highlights the use of proteomic studies to uncover non-genetic resistance mechanisms in cancer.

Acquired resistance to immunomodulatory drugs is common in multiple myeloma patients, but rarely attributed to genetic alterations. Here, proteomic, phosphoproteomic and RNA sequencing analysis in five paired pre-treatment and relapse samples reveals a CDK6-regulated protein resistance signature.

Combination therapy targeting Erk1/2 and CDK4/6i in relapsed refractory multiple myeloma

Oncogenic activated RAS mutations have been detected in 50% of de novo and 70% of relapsed multiple myeloma (MM) patients. Translocation t(11;14) involving IgH/CCDN1 and overexpression of cyclin-Ds are early events in MM pathogenesis, enhancing uncontrolled MM cell growth. We hypothesized that targeting both RAS/MAPK pathway molecules including Erk1/2 along with cyclin-Ds enhances MM cytotoxicity and minimizes side effects. Recent studies have demonstrated the high potency of Erk1/2 and CDK4/6 inhibitors in metastatic relapsed cancers, and here we tested anti-MM effects of the Erk1/2 + CDK4/6 inhibitor combination. Our studies showed strong synergistic (IC < 0.5) cytotoxicity of Erk1/2i + CDK4/6i in MM-cells. Erk1/2i + CDK4/6i treatment in a dose-dependent manner arrested MM-cells in the G0/G1 phase and activated mitochondrial apoptotic signaling. Our studies showed that Erk1/2i + CDK4/6i treatment-induced inhibition of key target molecules in Erk1/2 and CDK4/6 signaling, such as c-myc, p-RSK, p-S6, p-RB, and E2F1, suggesting on-target activity of these inhibitors. We identified Erk1/2i + CDK4/6i treatment associated five-gene signature which includes SNRPB and SLC25A5; these genes are involved in RNA processing and mitochondrial metabolism, respectively. Overall, our studies provide the preclinical framework for Erk1/2i + CDK4/6i combination clinical trials to target Ras+CDK pathways to improve patient outcome in MM.

Discovery of novel and orally bioavailable CDK 4/6 inhibitors with high kinome selectivity, low toxicity and long-acting stability for the treatment of multiple myeloma

Multiple myeloma (MM) ranks second in malignant hematopoietic cancers, and the most common anti-MM drugs easily generate resistance. CDK4/6 have been validated to play determinant roles in MM, but no remarkable progress has been obtained from clinical trials of CDK4/6 inhibitors for MM. To discover novel CDK6 inhibitors with better potency and high druggability, structure-based virtual screening was conducted to identify compound 10. Further chemical optimization afforded a better derivative, compound 32, which exhibited strong inhibition of CDK4/6 and showed high selectivity over 360+ kinases, including homologous CDKs. The in vivo evaluation demonstrated that compound 32 possessed low toxicity (LD₅₀ > 10,000 mg/kg), favorable bioavailability (F% = 51%), high metabolic stability (t_1/2 > 24 h) and strong anti-MM potency. In summary, we discovered a novel CDK4/6 inhibitor bearing favorable drug-like properties and offered a great candidate for MM preclinical studies.

The role of microRNA-338-3p in cancer: growth, invasion, chemoresistance, and mediators

Cancer still remains as one of the leading causes of death worldwide. Metastasis and proliferation are abnormally increased in cancer cells that subsequently, mediate resistance of cancer cells to different therapies such as radio-, chemo- and immune-therapy. MicroRNAs (miRNAs) are endogenous short non-coding RNAs that can regulate expression of target genes at post-transcriptional level and capable of interaction with mRNA-coding genes. Vital biological mechanisms including apoptosis, migration and differentiation are modulated by these small molecules. MiRNAs are key players in regulating cancer proliferation and metastasis as well as cancer therapy response. MiRNAs can function as both tumor-suppressing and tumor-promoting factors. In the present review, regulatory impact of miRNA-338-3p on cancer growth and migration is discussed. This new emerging miRNA can regulate response of cancer cells to chemotherapy and radiotherapy. It seems that miRNA-338-3p has dual role in cancer chemotherapy, acting as tumor-promoting or tumor-suppressor factor. Experiments reveal anti-tumor activity of miRNA-338-3p in cancer. Hence, increasing miRNA-338-3p expression is of importance in effective cancer therapy. Long non-coding RNAs, circular RNAs and hypoxia are potential upstream mediators of miRNA-338-3p in cancer. Anti-tumor agents including baicalin and arbutin can promote expression of miRNA-338-3p in suppressing cancer progression. These topics are discussed to shed some light on function of miRNA-338-3p in cancer cells.

The Wee1 kinase inhibitor MK1775 suppresses cell growth, attenuates stemness and synergises with bortezomib in multiple myeloma

Multiple myeloma stem-like cells (MMSCs) are responsible for initiation and relapse, though novel treatment paradigms that effectively eradicate MMSCs are yet to be developed. Selective inhibition of the cell cycle regulatory kinase Wee1 by MK1775 is being explored as a potential anti-cancer therapeutic. We report that higher expression of Wee1 is correlated with poor survival in multiple myeloma (MM). The MM models and patient-derived CD138⁺ plasma cells are particularly sensitive to the growth-inhibitory effects of the Wee1 inhibitor MK1775. MK1775 induces Mus81-Eme1 endonuclease-mediated DNA damage in S-phase cell cycle that results in a blockade of replication and then apoptosis. Furthermore, MK1775 strongly suppresses the features of stemness in vitro, in vivo and in primary CD138⁺ cells by decreasing ALDH1⁺ cell fraction and the expression of ALDH1. In addition, co-treatment of MK1775 with bortezomib is synergistic in vitro and in vivo. Bortezomib, although it enhances ALDH1⁺ cells, when combined with MK1775 abrogates this stimulatory effect on stemness. Considering MM as an invariably incurable malignancy due to the presence of heterogenic myeloma stem-like cells, our study presents inhibition of Wee1 as a promising targeted therapy for MM and provides a compelling rationale to further investigate the activity of MK1775 against myeloma in clinical settings.

Targeting CDK4/6 in mantle cell lymphoma

Targeting the cell cycle represents a rational approach to mantle cell lymphoma (MCL) therapy, as aberrant expression of cyclin D1 and dysregulation of CDK4 underlie cell cycle progression and proliferation of MCL cells. Although cell cycle cancer therapy was historically ineffective due to a lack of selective and effective drugs, this landscape changed with the advent of selective and potent small-molecule oral CDK4/6 inhibitors. Here, we review the anti-tumor activities and clinical data of selective CDK4/6 inhibitors in MCL. We summarize the known mechanism of action of palbociclib, the most specific CDK4/6 inhibitor to date, and the strategy to leverage this specificity to reprogram MCL for a deeper and more durable clinical response to partner drugs. We also discuss integrative longitudinal functional genomics as a strategy to discover tumor-intrinsic genomic biomarkers and tumor-immune interactions that potentially contribute to the clinical response to palbociclib in combination therapy for MCL. Understanding the genomic basis for targeting CDK4/6 and the mechanisms of action and resistance in MCL may advance personalized therapy for MCL and shed light on drug resistance in other cancers.

MAGE-A inhibit apoptosis and promote proliferation in multiple myeloma through regulation of BIM and p21Cip1

The type I Melanoma Antigen Gene (MAGE) A3 is a functional target associated with survival and proliferation in multiple myeloma (MM). To investigate the mechanisms of these oncogenic functions, we performed gene expression profiling (GEP) of p53 wild-type human myeloma cell lines (HMCL) after MAGE-A knockdown, which identified a set of 201 differentially expressed genes (DEG) associated with apoptosis, DNA repair, and cell cycle regulation. MAGE knockdown increased protein levels of pro-apoptotic BIM and of the endogenous cyclin-dependent kinase (CDK) inhibitor p21Cip1. Depletion of MAGE-A in HMCL increased sensitivity to the alkylating agent melphalan but not to proteasome inhibition. High MAGEA3 was associated with the MYC and Cell Cycling clusters defined by a network model of GEP data from the CoMMpass database of newly diagnosed, untreated MM patients. Comparative analysis of CoMMpass subjects based on high or low MAGEA3 expression revealed a set of 6748 DEG that also had significant functional associations with cell cycle and DNA replication pathways, similar to that observed in HMCL. High MAGEA3 expression correlated with shorter overall survival after melphalan chemotherapy and autologous stem cell transplantation (ASCT). These results demonstrate that MAGE-A3 regulates Bim and p21Cip1 transcription and protein expression, inhibits apoptosis, and promotes proliferation.

Potent anti-myeloma activity of the TOPK inhibitor OTS514 in pre-clinical models

Multiple myeloma (MM) continues to be considered incurable, necessitating new drug discovery. The mitotic kinase T‐LAK cell‐originated protein kinase/PDZ‐binding kinase (TOPK/PBK) is associated with proliferation of tumor cells, maintenance of cancer stem cells, and poor patient prognosis in many cancers. In this report, we demonstrate potent anti‐myeloma effects of the TOPK inhibitor OTS514 for the first time. OTS514 induces cell cycle arrest and apoptosis at nanomolar concentrations in a series of human myeloma cell lines (HMCL) and prevents outgrowth of a putative CD138⁺ stem cell population from MM patient‐derived peripheral blood mononuclear cells. In bone marrow cells from MM patients, OTS514 treatment exhibited preferential killing of the malignant CD138⁺ plasma cells compared with the CD138⁻ compartment. In an aggressive mouse xenograft model, OTS964 given orally at 100 mg/kg 5 days per week was well tolerated and reduced tumor size by 48%‐81% compared to control depending on the initial graft size. FOXO3 and its transcriptional targets CDKN1A (p21) and CDKN1B (p27) were elevated and apoptosis was induced with OTS514 treatment of HMCLs. TOPK inhibition also induced loss of FOXM1 and disrupted AKT, p38 MAPK, and NF‐κB signaling. The effects of OTS514 were independent of p53 mutation or deletion status. Combination treatment of HMCLs with OTS514 and lenalidomide produced synergistic effects, providing a rationale for the evaluation of TOPK inhibition in existing myeloma treatment regimens.

Long non‑coding RNA TP73 antisense RNA 1 facilitates the proliferation and migration of cervical cancer cells via regulating microRNA‑607/cyclin D2

The present study aimed to explore the effect of the long non‑coding RNA TP73 antisense RNA 1 (TP73‑AS1) on cervical cancer progression. Cervical cancer and adjacent tissues were collected from 56 patients and assessed. In addition, HeLa and CaSki cells were transfected with various plasmids, inhibitors and corresponding controls, and then Cell Counting Kit‑8 and Transwell assays were used to detect the cell proliferation, migration and invasion abilities. Luciferase reporter gene assay was also performed in HeLa cells. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was used to investigate TP73‑AS1, microRNA‑607 (miR‑607) and cyclin D2 (CCND2) gene expression, while CCND2 protein expression was determined by western blot analysis. The results revealed that the TP73‑AS1 level was upregulated in cervical cancer tissues (P<0.05) and predicted a poor 5‑year overall survival (P<0.05). HeLa and CaSki cells transfected with siTP73‑AS1 exhibited reduced proliferation, migration and invasion abilities when compared with those in the siNC group (P<0.05). Furthermore, miR‑607 was found to be negatively regulated by TP73‑AS1, while CCND2 was negatively regulated by miR‑607. HeLa and CaSki cells transfected with siTP73‑AS1 exhibited lower CCND2 mRNA and protein expression levels compared with the siNC and siTP73‑AS1 + miR‑inhibitor groups (P<0.05). Compared with the siNC and siTP73‑AS1 + CCND2 overexpression groups, siTP73‑AS1‑transfected HeLa and CaSki cells had decreased proliferation, migration and invasion abilities (P<0.05). In conclusion, the findings suggested that upregulation of TP73‑AS1 promoted cervical cancer progression by promoting CCND2 via the suppression of miR‑607 expression.

Zingerone Suppresses Tumor Development through Decreasing Cyclin D1 Expression and Inducing Mitotic Arrest

Cancer cells undergo uncontrolled proliferation resulting from aberrant activity of various cell-cycle proteins. Therefore, despite recent advances in intensive chemotherapy, it is difficult to cure cancer completely. Recently, cell-cycle regulators became attractive targets in cancer therapy. Zingerone, a phenolic compound isolated from ginger, is a nontoxic and inexpensive compound with varied pharmacological activities. In this study, the therapeutic effect of zingerone as an anti-mitotic agent in human neuroblastoma cells was investigated. Following treatment of BE(2)-M17 cells with zingerone, we performed a 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay and colony-formation assay to evaluate cellular proliferation, in addition to immunofluorescence cytochemistry and flow cytometry to examine the mitotic cells. The association of gene expression with tumor stage and survival was analyzed. Furthermore, to examine the anti-cancer effect of zingerone, we applied a BALB/c mouse-tumor model using a BALB/c-derived adenocarcinoma cell line. In human neuroblastoma cells, zingerone inhibited cellular viability and survival. Moreover, the number of mitotic cells, particularly those in prometaphase, increased in zingerone-treated neuroblastoma cells. Regarding specific molecular mechanisms, zingerone decreased cyclin D1 expression and induced the cleavage of caspase-3 and poly (ADP-ribose) polymerase 1 (PARP-1). The decrease in cyclin D1 and increase in histone H3 phosphorylated (p)-Ser10 were confirmed by immunohistochemistry in tumor tissues administered with zingerone. These results suggest that zingerone induces mitotic arrest followed by inhibition of growth of neuroblastoma cells. Collectively, zingerone may be a potential therapeutic drug for human cancers, including neuroblastoma.

Gli3 controls the onset of cortical neurogenesis by regulating the radial glial cell cycle through Cdk6 expression

The cerebral cortex contains an enormous number of neurons, allowing it to perform highly complex neural tasks. Understanding how these neurons develop at the correct time and place and in accurate numbers constitutes a major challenge. Here, we demonstrate a novel role for Gli3, a key regulator of cortical development, in cortical neurogenesis. We show that the onset of neuron formation is delayed in Gli3 conditional mouse mutants. Gene expression profiling and cell cycle measurements indicate that shortening of the G1 and S phases in radial glial cells precedes this delay. Reduced G1 length correlates with an upregulation of the cyclin-dependent kinase gene Cdk6, which is directly regulated by Gli3. Moreover, pharmacological interference with Cdk6 function rescues the delayed neurogenesis in Gli3 mutant embryos. Overall, our data indicate that Gli3 controls the onset of cortical neurogenesis by determining the levels of Cdk6 expression, thereby regulating neuronal output and cortical size.

MicroRNA-338-3p Inhibits Proliferation and Promotes Apoptosis of Multiple Myeloma Cells Through Targeting Cyclin-Dependent Kinase 4

MicroRNA-338-3p (miR-338-3p) has been reported to be a tumor suppressor in multiple cancer types. However, the biological role of miR-338-3p and its underlying mechanism in multiple myeloma (MM) remain unclear. In the present study, we investigated the biological role and potential of miR-338-3p in MM. We found that miR-338-3p was significantly decreased in newly diagnosed and relapsed MM tissues and cell lines. Overexpression of miR-338-3p in MM cells significantly inhibited proliferation and promoted apoptosis, caspase 3, and caspase 8 activity. Bioinformatics algorithm analysis predicted that cyclin-dependent kinase 4 (CDK4) was a direct target of miR-338-3p, and this was experimentally verified by a dual-luciferase reporter assay. Furthermore, overexpression of miR-338-3p inhibited CDK4 expression on mRNA and protein levels. Of note, the restoration of CDK4 expression markedly abolished the effect of miR-338-3p overexpression on cell proliferation, apoptosis, caspase 3, and caspase 8 activities in MM cells. Taken together, the present study is the first to demonstrate that miR-338-3p functions as a tumor suppressor in MM through inhibiting CDK4. This finding implies that miR-338-3p is a potential therapeutic target for the treatment of MM.

Design and synthesis of 4-(2,3-dihydro-1H-benzo[d]pyrrolo[1,2-a]imidazol-7-yl)-N-(5-(piperazin-1-ylmethyl)pyridine-2-yl)pyrimidin-2-amine as a highly potent and selective cyclin-dependent kinases 4 and 6 inhibitors and the discovery of structure-activity relationships

Cyclin-dependent kinases 4/6 play an important role in regulation of cell cycle, and overexpress in a variety of cancers. Up to now, new CDK inhibitors still need to be developed due to its poor selectivity. Herein we report a novel series of 4-(2,3-dihydro-1H-benzo[d]pyrrolo[1,2-a]imidazole-7-yl)-N-(5-(piperazin-1-ylmethyl)pyridine-2-yl)pyrimidin-2-amine anologues as potent CDK 4/6 inhibitors based on LY2835219 (Abemaciclib). Compound 10d, which exhibits approximate potency on CDK4/6 (IC₅₀ = 7.4/0.9 nM), has both good pharmacokinetic characters and high selectivity on CDK1 compared with LY2835219. Overall, compound 10d could be a promising candidate and a good starting point as anticancer drugs.

The therapeutic potential of cell cycle targeting in multiple myeloma

Proper cell cycle progression through the interphase and mitosis is regulated by coordinated activation of important cell cycle proteins (including cyclin-dependent kinases and mitotic kinases) and several checkpoint pathways. Aberrant activity of these cell cycle proteins and checkpoint pathways results in deregulation of cell cycle progression, which is one of the key hallmarks of cancer. Consequently, intensive research on targeting these cell cycle regulatory proteins identified several candidate small molecule inhibitors that are able to induce cell cycle arrest and even apoptosis in cancer cells. Importantly, several of these cell cycle regulatory proteins have also been proposed as therapeutic targets in the plasma cell malignancy multiple myeloma (MM). Despite the enormous progress in the treatment of MM the past 5 years, MM still remains most often incurable due to the development of drug resistance. Deregulated expression of the cyclins D is observed in virtually all myeloma patients, emphasizing the potential therapeutic interest of cyclin-dependent kinase inhibitors in MM. Furthermore, other targets have also been identified in MM, such as microtubules, kinesin motor proteins, aurora kinases, polo-like kinases and the anaphase promoting complex/cyclosome. This review will provide an overview of the cell cycle proteins and checkpoint pathways deregulated in MM and discuss the therapeutic potential of targeting proteins or protein complexes involved in cell cycle control in MM.

A novel small molecule agent displays potent anti-myeloma activity by inhibiting the JAK2-STAT3 signaling pathway

The oncogenic STAT3 signaling pathway is emerging as a promising target for the treatment of multiple myeloma (MM). In the present study, we identified a novel STAT3 inhibitor SC99 in a target-based high throughput screen. SC99 inhibited JAK2-STAT3 activation but had no effects on other transcription factors such as NF-κB, and kinases such as AKT, ERK, and c-Src that are in association with STAT3 signaling pathway. Furthermore, SC99 downregulated the expression of STAT3-modulated genes, including Bcl-2, Bcl-xL, VEGF, cyclin D2, and E2F-1. By inhibiting the STAT3 signaling, SC99 induced MM cell apoptosis which could be partly abolished by the ectopic expression of STAT3. Furthermore, SC99 displayed potent anti-MM activity in two independent MM xenograft models in nude mice. Oral administration of SC99 led to marked decrease of tumor growth within 10 days at a daily dosage of 30 mg/kg, but did not raise toxic effects. Taken together, this study identified a novel oral JAK2/STAT3 inhibitor that could be developed as an anti-myeloma agent.

The genetic and genomic background of multiple myeloma patients achieving complete response after induction therapy with bortezomib, thalidomide and dexamethasone (VTD)

The prime focus of the current therapeutic strategy for Multiple Myeloma (MM) is to obtain an early and deep tumour burden reduction, up to the level of complete response (CR). To date, no description of the characteristics of the plasma cells (PC) prone to achieve CR has been reported. This study aimed at the molecular characterization of PC obtained at baseline from MM patients in CR after bortezomib-thalidomide-dexamethasone (VTD) first line therapy.

One hundred and eighteen MM primary tumours obtained from homogeneously treated patients were profiled both for gene expression and for single nucleotide polymorphism genotype. Genomic results were used to obtain a predictor of sensitivity to VTD induction therapy, as well as to describe both the transcription and the genomic profile of PC derived from MM with subsequent optimal response to primary induction therapy.

By analysing the gene profiles of CR patients, we identified a 5-gene signature predicting CR with an overall median accuracy of 75% (range: 72%–85%). In addition, we highlighted the differential expression of a series of genes, whose deregulation might explain patients' sensitivity to VTD therapy. We also showed that a small copy number loss, covering 606Kb on chromosome 1p22.1 was the most significantly associated with CR patients.

Mutations in the CCND1 and CCND2 genes are frequent events in adult patients with t(8;21)(q22;q22) acute myeloid leukemia

Core-binding factor acute myeloid leukemia (CBF-AML) is defined by the presence of either t(8;21)(q22;q22)/RUNX1-RUNX1T1 or inv(16)(p13.1q22)/t(16;16)(p13.1;q22)/CBFB-MYH11. The resulting fusion genes require a 'second hit' to initiate leukemogenesis. Mutation assessment of 177 adults with CBF-AML, including 68 with t(8;21) and 109 with inv(16)/t(16;16), identified not only mutations well known in CBF-AML but also mutations in the CCND1 and CCND2 genes, which represent novel frequent molecular alterations in AML with t(8;21). Altogether, CCND1 (n=2) and CCND2 (n=8) mutations were detected in 10 (15%) patients with t(8;21) in our cohort. A single CCND2 mutation was also found in 1 (0.9%) patient with inv(16). In contrast, CCND1 and CCND2 mutations were detected in only 11 (0.77%) of 1426 non-CBF-AML patients. All CCND2 mutations cluster around the highly conserved amino-acid residue threonine 280 (Thr280). We show that Thr280Ala-mutated CCND2 leads to increased phosphorylation of the retinoblastoma protein, thereby causing significant cell cycle changes and increased proliferation of AML cell lines. The identification of CCND1 and CCND2 mutations as frequent mutational events in t(8;21) AML may provide further justification for cell cycle-directed therapy in this disease.

Cyclin D type does not influence cell cycle response to DNA damage caused by ionizing radiation in multiple myeloma tumours

Multiple myeloma (MM) is characterized by over-expression of cyclin D1 (CCND1) or D2 (CCND2), which control G1 phase cell-cycle progression. Proteolytic degradation of CCND1 (but not CCND2), resulting in G1 arrest, is reported in non-MM cells post-DNA damage, affecting DNA repair and survival. We examined the effect of ionizing radiation (IR) on D-cyclin levels and cell-cycle kinetics of MM cells, exploring differences based on D-cyclin expression. We showed that CCND1 is downregulated, whereas CCND2 is not, following IR. This did not lead to hypo-phosphorylation of retinoblastoma protein or G1 arrest. Both CCND1- and CCND2-expressing MM cells arrested in S/G2/M, and did not differ in other cell-cycle proteins or sensitivity to IR. When treated with a CDK4/6 inhibitor, both CCND1 and CCND2 MM cells arrested in G1 and therefore are subject to physiological regulation at this checkpoint. Immunoprecipitation showed that, despite CCND1 degradation following IR, sufficient protein remains bound to CDK4/6 to prevent G1 arrest. Aberrant expression of CCND1 driven from the IGH promoter in t(11;14) MM cells maintains progression through G1 to arrest in S/G2/M. Differential expression of D-cyclin does not appear to affect cell-cycle response to IR, and is unlikely to underlie differential sensitivity to DNA damage.

Comparative transcriptome analysis of papilla and skin in the sea cucumber, Apostichopus japonicus

Papilla and skin are two important organs of the sea cucumber. Both tissues have ectodermic origin, but they are morphologically and functionally very different. In the present study, we performed comparative transcriptome analysis of the papilla and skin from the sea cucumber (Apostichopus japonicus) in order to identify and characterize gene expression profiles by using RNA-Seq technology. We generated 30.6 and 36.4 million clean reads from the papilla and skin and de novo assembled in 156,501 transcripts. The Gene Ontology (GO) analysis indicated that cell part, metabolic process and catalytic activity were the most abundant GO category in cell component, biological process and molecular funcation, respectively. Comparative transcriptome analysis between the papilla and skin allowed the identification of 1,059 differentially expressed genes, of which 739 genes were expressed at higher levels in papilla, while 320 were expressed at higher levels in skin. In addition, 236 differentially expressed unigenes were not annotated with any database, 160 of which were apparently expressed at higher levels in papilla, 76 were expressed at higher levels in skin. We identified a total of 288 papilla-specific genes, 171 skin-specific genes and 600 co-expressed genes. Also, 40 genes in papilla-specific were not annotated with any database, 2 in skin-specific. Development-related genes were also enriched, such as fibroblast growth factor, transforming growth factor-β, collagen-α2 and Integrin-α2, which may be related to the formation of the papilla and skin in sea cucumber. Further pathway analysis identified ten KEGG pathways that were differently enriched between the papilla and skin. The findings on expression profiles between two key organs of the sea cucumber should be valuable to reveal molecular mechanisms involved in the development of organs that are related but with morphological differences in the sea cucumber.

MUC1-C drives MYC in multiple myeloma

Multiple myeloma (MM) cell lines and primary tumor cells are addicted to the MYC oncoprotein for survival. Little is known, however, about how MYC expression is upregulated in MM cells. The mucin 1 C-terminal subunit (MUC1-C) is an oncogenic transmembrane protein that is aberrantly expressed in MM cell lines and primary tumor samples. The present studies demonstrate that targeting MUC1-C with silencing by clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 editing or with the GO-203 inhibitor is associated with downregulation of MYC messenger RNA and protein. The results show that MUC1-C occupies the MYC promoter and thereby activates the MYC gene by a β-catenin/transcription factor 4 (TCF4)-mediated mechanism. In this way, MUC1-C (1) increases β-catenin occupancy on the MYC promoter, (2) forms a complex with β-catenin and TCF4, and, in turn, (3) drives MYC transcription. Analysis of MM cells using quantitative real-time reverse transcription polymerase chain reaction arrays further demonstrated that silencing MUC1-C is associated with downregulation of MYC target genes, including CCND2, hTERT, and GCLC Analysis of microarray data sets further demonstrated that MUC1 levels positively correlate with MYC expression in MM progression and in primary cells from over 800 MM patients. These findings collectively provide convincing evidence that MUC1-C drives MYC expression in MM.

Increased SHP-1 expression results in radioresistance, inhibition of cellular senescence, and cell cycle redistribution in nasopharyngeal carcinoma cells

Background

Radioresistance is the main limit to the efficacy of radiotherapy in nasopharyngeal carcinoma (NPC). SHP-1 is involved in cancer progression, but its role in radioresistance and senescence of NPC is not well understood. This study aimed to assess the role of SHP-1 in the radioresistance and senescence of NPC cells.

Methods

SHP-1 was knocked-down and overexpressed in CNE-1 and CNE-2 cells using lentiviruses. Cells were irradiated to observe their radiosensitivity by colony forming assay. BrdU incorporation assay and flow cytometry were used to monitor cell cycle. A β-galactosidase assay was used to assess senescence. Western blot was used to assess SHP-1, p21, p53, pRb, Rb, H3K9Me3, HP1γ, CDK4, cyclin D1, cyclin E, and p16 protein expressions.

Results

Compared with CNE-1-scramble shRNA cells, SHP-1 downregulation resulted in increased senescence (+107 %, P < 0.001), increased radiosensitivity, higher proportion of cells in G0/G1 (+33 %, P < 0.001), decreased expressions of CDK4 (−44 %, P < 0.001), cyclin D1 (−41 %, P = 0.001), cyclin E (−97 %, P < 0.001), Rb (−79 %, P < 0.001), and pRb (−76 %, P = 0.001), and increased expression of p16 (+120 %, P = 0.02). Furthermore, SHP-1 overexpression resulted in radioresistance, inhibition of cellular senescence, and cell cycle arrest in the S phase. Levels of p53 and p21 were unchanged in both cell lines (all P > 0.05).

Conclusion

SHP-1 has a critical role in radioresistance, cell cycle progression, and senescence of NPC cells. Down-regulating SHP-1 may be a promising therapeutic approach for treating patients with NPC.

Tumor-suppressor Genes, Cell Cycle Regulatory Checkpoints, and the Skin

The cell cycle (or cell-division cycle) is a series of events that take place in a cell, leading to its division and duplication. Cell division requires cell cycle checkpoints (CPs) that are used by the cell to both monitor and regulate the progress of the cell cycle. Tumor-suppressor genes (TSGs) or antioncogenes are genes that protect the cell from a single event or multiple events leading to cancer. When these genes mutate, the cell can progress to a cancerous state. We aimed to perform a narrative review, based on evaluation of the manuscripts published in MEDLINE-indexed journals using the Medical Subject Headings (MeSH) terms “tumor suppressor's genes,” “skin,” and “cell cycle regulatory checkpoints.” We aimed to review the current concepts regarding TSGs, CPs, and their association with selected cutaneous diseases. It is important to take into account that in some cell cycle disorders, multiple genetic abnormalities may occur simultaneously. These abnormalities may include intrachromosomal insertions, unbalanced division products, recombinations, reciprocal deletions, and/or duplication of the inserted segments or genes; thus, these presentations usually involve several genes. Due to their complexity, these disorders require specialized expertise for proper diagnosis, counseling, personal and family support, and genetic studies. Alterations in the TSGs or CP regulators may occur in many benign skin proliferative disorders, neoplastic processes, and genodermatoses.

miR-340 inhibits glioblastoma cell proliferation by suppressing CDK6, cyclin-D1 and cyclin-D2

Glioblastoma development is often associated with alteration in the activity and expression of cell cycle regulators, such as cyclin-dependent kinases (CKDs) and cyclins, resulting in aberrant cell proliferation. Recent studies have highlighted the pivotal roles of miRNAs in controlling the development and growth of glioblastoma. Here, we provide evidence for a function of miR-340 in the inhibition of glioblastoma cell proliferation. We found that miR-340 is downregulated in human glioblastoma tissue samples and several established glioblastoma cell lines. Proliferation and neurosphere formation assays revealed that miR-340 plays an oncosuppressive role in glioblastoma, and that its ectopic expression causes significant defect in glioblastoma cell growth. Further, using bioinformatics, luciferase assay and western blot, we found that miR-340 specifically targets the 3'UTRs of CDK6, cyclin-D1 and cyclin-D2, leading to the arrest of glioblastoma cells in the G0/G1 cell cycle phase. Confirming these results, we found that re-introducing CDK6, cyclin-D1 or cyclin-D2 expression partially, but significantly, rescues cells from the suppression of cell proliferation and cell cycle arrest mediated by miR-340. Collectively, our results demonstrate that miR-340 plays a tumor-suppressive role in glioblastoma and may be useful as a diagnostic biomarker and/or a therapeutic avenue for glioblastoma.

Hbp1 regulates the timing of neuronal differentiation during cortical development by controlling cell cycle progression

In the developing mammalian brain, neural stem cells (NSCs) initially expand the progenitor pool by symmetric divisions. NSCs then shift from symmetric to asymmetric division and commence neurogenesis. Although the precise mechanisms regulating the developmental timing of this transition have not been fully elucidated, gradual elongation in the length of the cell cycle and coinciding accumulation of determinants that promote neuronal differentiation may function as a biological clock that regulates the onset of asymmetric division and neurogenesis. We conducted gene expression profiling of embryonic NSCs in the cortical regions and found that expression of high mobility group box transcription factor 1 (Hbp1) was upregulated during neurogenic stages. Induced conditional knockout mice of Hbp1 generated by crossing with Nestin-CreERT2 mice exhibited a remarkable dilatation of the telencephalic vesicles with a tangentially expanded ventricular zone and a thinner cortical plate containing reduced numbers of neurons. In these Hbp1-deficient mouse embryos, neural stem/progenitor cells continued to divide with a shorter cell cycle length. And downstream target genes of the Wnt signaling, such as cyclin D1 and c-jun, were upregulated in the germinal zone of the cortical regions. These results indicate that Hbp1 plays a critical role in regulating the timing of cortical neurogenesis by elongating the cell cycle and is essential for normal cortical development.

Using the neurofibromatosis tumor predisposition syndromes to understand normal nervous system development

Development is a tightly regulated process that involves stem cell self-renewal, differentiation, cell-to-cell communication, apoptosis, and blood vessel formation. These coordinated processes ensure that tissues maintain a size and architecture that is appropriate for normal tissue function. As such, tumors arise when cells acquire genetic mutations that allow them to escape the normal growth constraints. In this regard, the study of tumor predisposition syndromes affords a unique platform to better understand normal development and the process by which normal cells transform into cancers. Herein, we review the processes governing normal brain development, discuss how brain cancer represents a disruption of these normal processes, and highlight insights into both normal development and cancer made possible by the study of tumor predisposition syndromes.

Novel targeted agents in the treatment of multiple myeloma

New, next-generation targeted treatment strategies are required to improve outcomes in patients with multiple myeloma (MM). Monoclonal antibodies, cell signaling inhibitors, and selective therapies targeting the bone marrow microenvironment have demonstrated encouraging results with generally manageable toxicity in therapeutic trials of patients with relapsed and refractory disease, each critically informed by preclinical studies. A combination approach of these newer agents with immunomodulators and/or proteasome inhibitors as part of a treatment platform seems to improve the efficacy of anti-MM regimens, even in heavily pretreated patients. Future studies are required to better understand the complex mechanisms of drug resistance in MM.

Association between the polymorphism rs3217927 of CCND2 and the risk of childhood acute lymphoblastic leukemia in a Chinese population

CyclinD proteins, the ultimate recipients of mitogenic and oncogenic signals, play a crucial role in cell-cycle regulation. CyclinD2, one of the cyclinD family, is overexpressed in T-acute lymphoblastic leukemia (ALL) and B-cell chronic lymphocytic leukemia and involved in the pathogenesis of leukemias. Recent reports indicated that CCND2 polymorphisms are associated with human cancer risk, thusly we hypothesized that CCND2 gene polymorphisms may contribute to childhood ALL susceptibility. We selected the polymorphism rs3217927 located in the 3'UTR region of CCND2 to assess its associations with childhood ALL risk in a case-control study. A significant difference was found in the genotype distributions of rs3217927 polymorphism between cases and controls (P = 0.019) and homozygous GG genotype may be an increased risk factor for childhood ALL (adjusted OR  =  1.84, 95% CI  =  1.14 -2.99). Furthermore, this increased risk was more pronounced with GG genotype among high-risk ALL (adjusted OR  = 1.95, 95% CI  =  1.04-3.67), low-risk ALL (adjusted OR  =  2.09, 95% CI  =  1.13-3.87), B-phenotype ALL patients (adjusted OR  =  1.78, 95% CI  =  1.08-2.95) and T-phenotype ALL patients (adjusted OR  =  2.87, 95% CI  =  1.16-7.13). Our results provide evidence that CCND2 polymorphism rs3217927 may be involved in the etiology of childhood ALL, and the GG genotype of rs3217927 may modulate the genetic susceptibility to childhood ALL in the Chinese population. Further functional studies and investigations in larger populations should be conducted to validate our findings.

Characterization of a Dual CDC7/CDK9 Inhibitor in Multiple Myeloma Cellular Models

Two key features of myeloma cells are the deregulation of the cell cycle and the dependency on the expression of the BCL2 family of anti-apoptotic proteins. The cell division cycle 7 (CDC7) is an essential S-phase kinase and emerging CDC7 inhibitors are effective in a variety of preclinical cancer models. These compounds also inhibit CDK9 which is relevant for MCL-1 expression. The activity and mechanism of action of the dual CDC7/CDK9 inhibitor PHA-767491 was assessed in a panel of multiple myeloma cell lines, in primary samples from patients, in the presence of stromal cells and in combination with drugs used in current chemotherapeutic regimens. We report that in all conditions myeloma cells undergo cell death upon PHA-767491 treatment and we report an overall additive effect with melphalan, bortezomib and doxorubicin, thus supporting further assessment of targeting CDC7 and CDK9 in multiple myeloma.

Pax6 exerts regional control of cortical progenitor proliferation via direct repression of Cdk6 and hypophosphorylation of pRb

The mechanisms by which early spatiotemporal expression patterns of transcription factors such as Pax6 regulate cortical progenitors in a region-specific manner are poorly understood. Pax6 is expressed in a gradient across the developing cortex and is essential for normal corticogenesis. We found that constitutive or conditional loss of Pax6 increases cortical progenitor proliferation by amounts that vary regionally with normal Pax6 levels. We compared the gene expression profiles of equivalent Pax6-expressing progenitors isolated from Pax6^+/+ and Pax6^−/− cortices and identified many negatively regulated cell-cycle genes, including Cyclins and Cdks. Biochemical assays indicated that Pax6 directly represses Cdk6 expression. Cyclin/Cdk repression inhibits retinoblastoma protein (pRb) phosphorylation, thereby limiting the transcription of genes that directly promote the mechanics of the cell cycle, and we found that Pax6 inhibits pRb phosphorylation and represses genes involved in DNA replication. Our results indicate that Pax6’s modulation of cortical progenitor cell cycles is regional and direct.

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Pax6 loss increases cortical progenitor proliferation by region-specific amounts

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The size of this effect correlates directly with normal Pax6 expression levels

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Expression of many key cell-cycle regulators is increased in the absence of Pax6

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Pax6 directly represses Cdk6 expression and controls pRb phosphorylation

Immunomodulation as a therapeutic strategy in the treatment of multiple myeloma

Growth and survival of multiple myeloma (MM) cells depend on intrinsic, cell-autonomous parameters, such as the genetic lesions harboured by the MM cells, as well as extracellular, cell-non-autonomous factors, including the interaction between MM cells and bone-marrow stromal cells and the suppression of the host's anticancer immune responses. Thalidomide and the immunomodulatory agents lenalidomide and pomalidomide have pleiotropic effects on MM cells and their microenvironment, including promotion of direct mechanisms of MM-cell apoptosis, as well as indirect mechanisms mediated by perturbation of cell adhesion, modulation of cytokine production, and inhibition of tumor-associated angiogenesis. The immunomodulatory properties of these agents are mediated by effects on T-cell proliferation and function, stimulation of natural killer cells, and inhibition of regulatory T cells. Thalidomide and lenalidomide have established roles in the treatment of patients with newly diagnosed MM and those with relapsed/refractory disease. Pomalidomide is currently being evaluated in clinical trials, and preliminary clinical data suggest that it is active in patients with MM that is refractory to lenalidomide and bortezomib treatment. This article provides an overview of the current and potential future roles of immunomodulation in the management of MM, and how improved anticancer immune responses may improve treatment outcomes.

Hypodiploid multiple myeloma is characterized by more aggressive molecular markers than non-hyperdiploid multiple myeloma

Multiple myeloma can be categorized into hyperdiploid or non-hyperdiploid myeloma based on the number of chromosomes found in the tumor clone. Among the non-hyperdiploid myelomas, the hypodiploid subtype has the most aggressive clinical phenotype, but the genetic differences between groups are not completely defined. In order to understand the genetic background of hypodiploid multiple myeloma better, we compared the genomic (array-based comparative genomic hybridization) and transcriptomic (gene expression profiling) background of 49 patients with hypodiploid myeloma with 50 other non-hyperdiploid and 125 hyperdiploid myeloma patients. There were significant chromosomal and gene expression differences between hyperdiploid patients and non-hyperdiploid and hypodiploid patients. Non-hyperdiploid and hypodiploid patients shared most of the chromosomal abnormalities; nevertheless a subset of these abnormalities, such as monosomies 13, 14 and 22, was markedly increased in hypodiploid patients. Furthermore, deletions of 1p, 12p, 16q and 17p, all associated with poor outcome or progression in multiple myeloma, were significantly enriched in hypodiploid patients. Molecular risk-stratification indices reinforce the worse prognosis associated with hypodiploid multiple myeloma compared with non-hyperdiploid multiple myeloma. Gene expression profiling clustered hypodiploid and non-hyperdiploid subgroups closer than hyperdiploid myeloma but also highlighted the up-regulation of CCND2, WHSC1/MMSET and FGFR3 in the hypodiploid subtype. In summary, hypodiploid multiple myeloma is genetically similar to non-hyperdiploid multiple myeloma but characterized by a higher prevalence of genetic alterations associated with poor outcome and disease progression. It is provocative to hypothesize that hypodiploid multiple myeloma is an advanced stage of non-hyperdiploid multiple myeloma.

Correlation between eight-gene expression profiling and response to therapy of newly diagnosed multiple myeloma patients treated with thalidomide-dexamethasone incorporated into double autologous transplantation

We performed a molecular study aimed at identifying a gene expression profile (GEP) signature predictive of attainment of at least near complete response (CR) to thalidomide-dexamethasone (TD) as induction regimen in preparation for double autologous stem cell transplantation in 112 younger patients with newly diagnosed multiple myeloma. A GEP supervised analysis was performed on a training set of 32 patients, allowing to identify 157 probe sets differentially expressed in patients with CR versus those failing CR to TD. We then generated an eight-gene GEP signature whose performance was subsequently validated in a training set of 80 patients. A correct prediction of response to TD was found in 71 % of the cases analyzed. The eight genes were downregulated in patients who achieved CR to TD. Comparisons between post-autotransplantation outcomes of the 44 non-CR-predicted patients and of the 36 CR-predicted patients showed that this latter subgroup had a statistically significant benefit in terms of higher rate of CR after autotransplant(s) and longer time to progression, event-free survival, and overall survival. These results can be an important first step to identify at diagnosis those patients who will respond more favourably to a particular treatment strategy.

Mithramycin exerts an anti-myeloma effect and displays anti-angiogenic effects through up-regulation of anti-angiogenic factors

Mithramycin (MTM), a cytotoxic compound, is currently being investigated for its anti-angiogenic activity that seems to be mediated through an inhibition of the transcription factor SP1. In this study we evaluated its anti-myeloma effects in the syngenic 5TGM1 model in vitro as well as in vivo. In vitro, MTM inhibited DNA synthesis of 5TGM1 cells with an IC50 of 400 nM and induced an arrest in cell cycle progression at the G1/S transition point. Western-blot revealed an up-regulation of p53, p21 and p27 and an inhibition of c-Myc, while SP1 remained unaffected. In rat aortic ring assays, a strong anti-angiogenic effect was seen, which could be explained by a decrease of VEGF production and an up-regulation of anti-angiogenic proteins such as IP10 after MTM treatment. The administration of MTM to mice injected with 5TGM1 decreased 5TGM1 cell invasion into bone marrow and myeloma neovascularisation. These data suggest that MTM displays anti-myeloma and anti-angiogenic effects that are not mediated by an inhibition of SP1 but rather through c-Myc inhibition and p53 activation.

Targeting cell cycle regulation in cancer therapy

Cell proliferation is an essential mechanism for growth, development and regeneration of eukaryotic organisms; however, it is also the cause of one of the most devastating diseases of our era: cancer. Given the relevance of the processes in which cell proliferation is involved, its regulation is of paramount importance for multicellular organisms. Cell division is orchestrated by a complex network of interactions between proteins, metabolism and microenvironment including several signaling pathways and mechanisms of control aiming to enable cell proliferation only in response to specific stimuli and under adequate conditions. Three main players have been identified in the coordinated variation of the many molecules that play a role in cell cycle: i) The cell cycle protein machinery including cyclin-dependent kinases (CDK)-cyclin complexes and related kinases, ii) The metabolic enzymes and related metabolites and iii) The reactive-oxygen species (ROS) and cellular redox status. The role of these key players and the interaction between oscillatory and non-oscillatory species have proved essential for driving the cell cycle. Moreover, cancer development has been associated to defects in all of them. Here, we provide an overview on the role of CDK-cyclin complexes, metabolic adaptations and oxidative stress in regulating progression through each cell cycle phase and transitions between them. Thus, new approaches for the design of innovative cancer therapies targeting crosstalk between cell cycle simultaneous events are proposed.

Prolonged early G(1) arrest by selective CDK4/CDK6 inhibition sensitizes myeloma cells to cytotoxic killing through cell cycle-coupled loss of IRF4

Dysregulation of cyclin-dependent kinase 4 (CDK4) and CDK6 by gain of function or loss of inhibition is common in human cancer, including multiple myeloma, but success in targeting CDK with broad-spectrum inhibitors has been modest. By selective and reversible inhibition of CDK4/CDK6, we have developed a strategy to both inhibit proliferation and enhance cytotoxic killing of cancer cells. We show that induction of prolonged early-G(1) arrest (pG1) by CDK4/CDK6 inhibition halts gene expression in early-G(1) and prevents expression of genes programmed for other cell-cycle phases. Removal of the early-G(1) block leads to S-phase synchronization (pG1-S) but fails to completely restore scheduled gene expression. Consequently, the IRF4 protein required to protect myeloma cells from apoptosis is markedly reduced in pG1 and further in pG1-S in response to cytotoxic agents, such as the proteasome inhibitor bortezomib. The coordinated loss of IRF4 and gain of Bim sensitize myeloma tumor cells to bortezomib-induced apoptosis in pG1 in the absence of Noxa and more profoundly in pG1-S in cooperation with Noxa in vitro. Induction of pG1 and pG1-S by reversible CDK4/CDK6 inhibition further augments tumor-specific bortezomib killing in myeloma xenografts. Reversible inhibition of CDK4/CDK6 in sequential combination therapy thus represents a novel mechanism-based cancer therapy.

Cyclin dependent kinases in cancer: potential for therapeutic intervention

Cell cycle progression through each phase is regulated by heterodimers formed by cyclin-dependent kinases (CDKs) and their regulatory partner proteins, the cyclins. Together they coordinate the cellular events through cell cycle. De-regulation of cell-cycle control due to aberrant CDK activity is a common feature of most cancer types. Intensive research on small molecules that target cell cycle regulatory proteins has led to the identification of many candidate inhibitors that are able to arrest proliferation and induce apoptosis in neoplastic cells as a promising strategy to treat cancer. Interestingly, cyclin-dependent kinases (CDKs) have also been proposed as therapeutic targets for Multiple Myeloma (MM). Overexpression and aberrant expression of the cyclins, specifically the D cyclins is seen in the majority of MM underscoring the value of exploring CDK inhibition in MM which currently remains an incurable neoplastic plasma-cell disorder. It is characterized by clonal proliferation of malignant plasma cells in the bone marrow microenviroment and associated organ dysfunction. Recent preclinical and early clinical data explore several CDK inhibitors in the context of MM. This review will provide an overview of the main classes of CDK inhibitors with a focus on their mechanism of action and discuss clinical and pharmacological implications of CDK inhibitors as possible therapeutic approaches for the treatment of cancer with specific consideration to MM.

The impact of cyclin D1 mRNA isoforms, morphology and p53 in mantle cell lymphoma: p53 alterations and blastoid morphology are strong predictors of a high proliferation index

BACKGROUND

Mantle cell lymphoma is a clinically heterogeneous disease characterized by overexpression of cyclin D1 protein. Blastoid morphology, high proliferation, and secondary genetic aberrations are markers of aggressive behavior. Expression profiling of mantle cell lymphoma revealed that predominance of the 3'UTR-deficient, short cyclin D1 mRNA isoform was associated with high cyclin D1 levels, a high "proliferation signature" and poor prognosis.

DESIGN AND METHODS

Sixty-two cases of mantle cell lymphoma were analyzed for cyclin D1 mRNA isoforms and total cyclin D1 levels by real-time reverse transcriptase polymerase chain reaction, and TP53 alterations were assessed by immunohistochemistry and molecular analysis. Results were correlated with proliferation index and clinical outcome.

RESULTS

Predominance of the short cyclin D1 mRNA was found in 14 (23%) samples, including four with complete loss of the standard transcript. TP53 alterations were found in 15 (24%) cases. Predominance of 3'UTR-deficient mRNA was significantly associated with high cyclin D1 mRNA levels (P=0.009) and more commonly found in blastoid mantle cell lymphoma (5/11, P=0.060) and cases with a proliferation index of >20% (P=0.026). Both blastoid morphology (11/11, P<0.001) and TP53 alterations (15/15, P<0.001) were significantly correlated with a high proliferation index. A proliferation index of 10% was determined to be a significant threshold for survival in multivariate analysis (P=0.01).

CONCLUSIONS

TP53 alterations are strongly associated with a high proliferation index and aggressive behavior in mantle cell lymphoma. Predominance of the 3'UTR-deficient transcript correlates with higher cyclin D1 levels and may be a secondary contributing factor to high proliferation, but failed to reach prognostic significance in this study.

Inhibition of cell cycle progression by dual phosphatidylinositol-3-kinase and mTOR blockade in cyclin D2 positive multiple myeloma bearing IgH translocations

Multiple myeloma (MM) is a clinically and genetically heterogenous cancer where tumour cells have dysregulated expression of a D-type cyclin, often in association with a recurrent IgH translocation. Patients whose tumour cells express cyclin D2, with the translocation t(4;14) or t(14;16), generally have more proliferative disease and inferior outcomes. The phosphatidylinositol-3-kinase (PI3K) pathway is a major regulator of D-type cyclin expression and cell cycle entry. We evaluated the effect of PI3K pathway blockade on cell cycle behaviour in MM cells, investigating differences between cyclin D2- and cyclin D1-expressing tumours. MM cell lines and primary bone marrow CD138⁺ MM cells were exposed to the pan-PI3K/mTOR inhibitor, PI-103, and assessed for cell cycle profiles, [³H]-thymidine uptake and cell cycle proteins. We report, in both cell lines and primary MM cells, that PI-103 induced cell cycle arrest with downregulation of cyclin D2 and CDK4/6 in MM cells expressing cyclin D2 via t(4;14) or t(14;16) translocations. Cells expressing cyclin D1 via t(11;14) were insensitive to PI-103, despite exhibiting inhibition of downstream signalling targets. In primary MM cells, PI-103 enhanced the anti-proliferative effects of anti-MM agents. Treatment paradigms including blockade of the PI3K/mTOR pathway should be targeted at patients with IgH translocations associated with cyclin D2 overexpression.