The pancancer overexpressed NFYC Antisense 1 controls cell cycle mitotic progression through in cis and in trans modes of action.

Antisense RNAs (asRNAs) represent an underappreciated yet crucial layer of gene expression regulation. Generally thought to modulate their sense genes in cis through sequence complementarity or their act of transcription, asRNAs can also regulate different molecular targets in trans, in the nucleus or in the cytoplasm. Here, we performed an in-depth molecular characterization of NFYC Antisense 1 (NFYC-AS1), the asRNA transcribed head-to-head to NFYC subunit of the proliferation-associated NF-Y transcription factor. Our results show that NFYC-AS1 is a prevalently nuclear asRNA peaking early in the cell cycle. Comparative genomics suggests a narrow phylogenetic distribution, with a probable origin in the common ancestor of mammalian lineages. NFYC-AS1 is overexpressed pancancer, preferentially in association with RB1 mutations. Knockdown of NFYC-AS1 by antisense oligonucleotides impairs cell growth in lung squamous cell carcinoma and small cell lung cancer cells, a phenotype recapitulated by CRISPR/Cas9-deletion of its transcription start site. Surprisingly, expression of the sense gene is affected only when endogenous transcription of NFYC-AS1 is manipulated. This suggests that regulation of cell proliferation is at least in part independent of the in cis transcription-mediated effect on NFYC and is possibly exerted by RNA-dependent in trans effects converging on the regulation of G2/M cell cycle phase genes. Accordingly, NFYC-AS1-depleted cells are stuck in mitosis, indicating defects in mitotic progression. Overall, NFYC-AS1 emerged as a cell cycle-regulating asRNA with dual action, holding therapeutic potential in different cancer types, including the very aggressive RB1-mutated tumors.

Effectiveness of irinotecan plus trabectedin on a desmoplastic small round cell tumor patient-derived xenograft.

This study exploited a novel patient-derived xenograft (PDX) of desmoplastic small round cell tumor (DSRCT), which reproduces histomorphological and molecular characteristics of the clinical tumor, to assess the activity of cytotoxic and targeted anticancer agents. Antitumor effect was moderate for doxorubicin, pazopanib and larotrectenib [maximum tumor volume inhibition (max TVI), 55-66%], while trabectedin had higher activity (max TVI, 82%). Vinorelbine, irinotecan and eribulin achieved nearly complete tumor growth inhibition (max TVI, 96-98%), although tumors regrew after the end of treatment. The combination of irinotecan with either eribulin or trabectedin resulted in complete responses, which were maintained until the end of the experiment for irinotecan plus trabectedin. Irinotecan-based combinations nearly abrogated the expression of proteins of the G2/M checkpoint, preventing cell entrance in mitosis, and induced apoptotic and necroptotic cell death. Consistently, irinotecan plus trabectedin resulted in reprogramming of DSCRT transcriptome, with downregulation of E2F targets, G2/M checkpoint and mitotic spindle gene sets. This study emphasizes the importance of patient-derived preclinical models to explore new treatments for DSRCT and fosters clinical investigation into the activity of irinotecan plus trabectedin.

Potential of the Stromal Matricellular Protein Periostin as a Biomarker to Improve Risk Assessment in Prostate Cancer.

Prostate cancer (PCa) ranges from indolent to aggressive tumors that may rapidly progress and metastasize. The switch to aggressive PCa is fostered by reactive stroma infiltrating tumor foci. Therefore, reactive stroma-based biomarkers may potentially improve the early detection of aggressive PCa, ameliorating disease classification. Gene expression profiles of PCa reactive fibroblasts highlighted the up-regulation of genes related to stroma deposition, including periostin and sparc. Here, the potential of periostin as a stromal biomarker has been investigated on PCa prostatectomies by immunohistochemistry. Moreover, circulating levels of periostin and sparc have been assessed in a low-risk PCa patient cohort enrolled in active surveillance (AS) by ELISA. We found that periostin is mainly expressed in the peritumoral stroma of prostatectomies, and its stromal expression correlates with PCa grade and aggressive disease features, such as the cribriform growth. Moreover, stromal periostin staining is associated with a shorter biochemical recurrence-free survival of PCa patients. Interestingly, the integration of periostin and sparc circulating levels into a model based on standard clinico-pathological variables improves its performance in predicting disease reclassification of AS patients. In this study, we provide the first evidence that circulating molecular biomarkers of PCa stroma may refine risk assessment and predict the reclassification of AS patients.

miR-550a-3p is a prognostic biomarker and exerts tumor-suppressive functions by targeting HSP90AA1 in diffuse malignant peritoneal mesothelioma.

Diffuse malignant peritoneal mesothelioma (DMPM) is a rare and rapidly lethal tumor, poorly responsive to conventional treatments. In this regards, the identification of molecular alterations underlying DMPM onset and progression might be exploited to develop novel therapeutic strategies. Here, we focused on miR-550a-3p, which we found downregulated in 45 DMPM clinical samples compared to normal tissues and whose expression levels were associated with patient outcome. Through a gain-of-function approach using miRNA mimics in 3 DMPM cell lines, we demonstrated the tumor-suppressive role of miR-550a-3p. Specifically, miRNA ectopic expression impaired cell proliferation and invasiveness, enhanced the apoptotic response, and reduced the growth of DMPM xenografts in mice. Antiproliferative and proapoptotic effects were also observed in prostate and ovarian cancer cell lines following miR-550a-3p ectopic expression. miR-550a-3p effects were mediated, at least in part, by the direct inhibition of HSP90AA1 and the consequent downregulation of its target proteins, the levels of which were rescued upon disruption of miRNA-HSP90AA1 mRNA pairing, partially abrogating miR-550a-3p-induced cellular effects. Our results show that miR-550a-3p reconstitution affects several tumor traits, thus suggesting this approach as a potential novel therapeutic strategy for DMPM.

Prediction of Grade Reclassification of Prostate Cancer Patients on Active Surveillance through the Combination of a Three-miRNA Signature and Selected Clinical Variables.

Active surveillance (AS) has evolved as a strategy alternative to radical treatments for very low risk and low-risk prostate cancer (PCa). However, current criteria for selecting AS patients are still suboptimal. Here, we performed an unprecedented analysis of the circulating miRNome to investigate whether specific miRNAs associated with disease reclassification can provide risk refinement to standard clinicopathological features for improving patient selection. The global miRNA expression profiles were assessed in plasma samples prospectively collected at baseline from 386 patients on AS included in three independent mono-institutional cohorts (training, testing and validation sets). A three-miRNA signature (miR-511-5p, miR-598-3p and miR-199a-5p) was found to predict reclassification in all patient cohorts (training set: AUC 0.74, 95% CI 0.60-0.87, testing set: AUC 0.65, 95% CI 0.51-0.80, validation set: AUC 0.68, 95% CI 0.56-0.80). Importantly, the addition of the three-miRNA signature improved the performance of the clinical model including clinicopathological variables only (AUC 0.70, 95% CI 0.61-0.78 vs. 0.76, 95% CI 0.68-0.84). Overall, we trained, tested and validated a three-miRNA signature which, combined with selected clinicopathological variables, may represent a promising biomarker to improve on currently available clinicopathological risk stratification tools for a better selection of truly indolent PCa patients suitable for AS.

MicroRNAs as Epigenetic Determinants of Treatment Response and Potential Therapeutic Targets in Prostate Cancer.

Prostate cancer (PCa) is the second most common tumor in men worldwide, and the fifth leading cause of male cancer-related deaths in western countries. PC is a very heterogeneous disease, meaning that optimal clinical management of individual patients is challenging. Depending on disease grade and stage, patients can be followed in active surveillance protocols or undergo surgery, radiotherapy, hormonal therapy, and chemotherapy. Although therapeutic advancements exist in both radiatiotherapy and chemotherapy, in a considerable proportion of patients, the treatment remains unsuccessful, mainly due to tumor poor responsiveness and/or recurrence and metastasis. microRNAs (miRNAs), small noncoding RNAs that epigenetically regulate gene expression, are essential actors in multiple tumor-related processes, including apoptosis, cell growth and proliferation, autophagy, epithelial-to-mesenchymal transition, invasion, and metastasis. Given that these processes are deeply involved in cell response to anti-cancer treatments, miRNAs have been considered as key determinants of tumor treatment response. In this review, we provide an overview on main PCa-related miRNAs and describe the biological mechanisms by which specific miRNAs concur to determine PCa response to radiation and drug therapy. Additionally, we illustrate whether miRNAs can be considered novel therapeutic targets or tools on the basis of the consequences of their expression modulation in PCa experimental models.

miR-34a-Mediated Survivin Inhibition Improves the Antitumor Activity of Selinexor in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is an aggressive disease with limited therapeutic options. Here, we pursued a combinatorial therapeutic approach to enhance the activity of selinexor, the first-in-class XPO1 inhibitor, by miR-34a ectopic expression in human TNBC experimental models. Anti-proliferative activity induced by selinexor and miR-34a expression, singly and in combination, was evaluated by MTS assay and cell counting. The effect of treatments on survivin and apoptosis-related proteins was assessed by western blotting and ELISA. The antitumor and toxic effects of individual and combined treatments were evaluated on TNBC orthotopic xenografts in SCID mice. Selinexor consistently showed anti-proliferative activity, although to a variable extent, in the different TNBC cell lines and caused the impairment of survivin expression and intracellular distribution, accompanied by apoptosis induction. Consistent with in vitro data, the XPO1 inhibitor variably affected the growth of TNBC orthotopic xenografts. miR-34a cooperated with selinexor to reduce survivin expression and improved its anti-proliferative activity in TNBC cells. Most importantly, miR-34a expression markedly enhanced selinexor antitumor activity in the less sensitive TNBC xenograft model, in absence of toxicity. Our data form a solid foundation for promoting the use of a miR-34a-based approach to improve the therapeutic efficacy of selinexor in TNBC patients.

SPOP Deregulation Improves the Radiation Response of Prostate Cancer Models by Impairing DNA Damage Repair.

Speckle-type POZ (pox virus and zinc finger protein) protein (SPOP) is the most commonly mutated gene in prostate cancer (PCa). Recent evidence reports a role of SPOP in DNA damage response (DDR), indicating a possible impact of SPOP deregulation on PCa radiosensitivity. This study aimed to define the role of SPOP deregulation (by gene mutation or knockdown) as a radiosensitizing factor in PCa preclinical models. To express WT or mutant (Y87N, K129E and F133V) SPOP, DU145 and PC-3 cells were transfected with pMCV6 vectors. Sensitivity profiles were assessed using clonogenic assay and immunofluorescent staining of γH2AX and RAD51 foci. SCID xenografts were treated with 5 Gy single dose irradiation using an image-guided small animal irradiator. siRNA and miRNA mimics were used to silence SPOP or express the SPOP negative regulator miR-145, respectively. SPOP deregulation, by either gene mutation or knockdown, consistently enhanced the radiation response of PCa models by impairing DDR, as indicated by transcriptome analysis and functionally confirmed by decreased RAD51 foci. SPOP silencing also resulted in a significant downregulation of RAD51 and CHK1 expression, consistent with the impairment of homologous recombination. Our results indicate that SPOP deregulation plays a radiosensitizing role in PCa by impairing DDR via downregulation of RAD51 and CHK1.

miR-1272 Exerts Tumor-Suppressive Functions in Prostate Cancer via HIP1 Suppression.

The development of novel therapies or the improvement of currently used approaches to treat prostate cancer (PCa), the most frequently diagnosed male tumor in developed countries, is an urgent need. In this regard, the functional characterization of microRNAs, molecules shown to regulate a number of cancer-related pathways, is instrumental to their possible clinical exploitation. Here, we demonstrate the tumor-suppressive role of the so far uncharacterized miR-1272, which we found to be significantly down-modulated in PCa clinical specimens compared to normal tissues. Through a gain-of-function approach using miRNA mimics, we showed that miR-1272 supplementation in two PCa cell models (DU145 and 22Rv1) reverted the mesenchymal phenotype by affecting migratory and invasive properties, and reduced cell growth in vitro and in vivo in SCID mice. Additionally, by targeting HIP1 encoding the endocytic protein HIP1, miR-1272 balanced EGFR membrane turnover, thus affecting the downstream AKT/ERK pathways, and, ultimately, increasing PCa cell response to ionizing radiation. Overall, our results show that miR-1272 reconstitution can affect several tumor traits, thus suggesting this approach as a potential novel therapeutic strategy to be pursued for PCa, with the multiple aim of reducing tumor growth, enhancing response to radiotherapy and limiting metastatic dissemination.

Core Biopsies from Prostate Cancer Patients in Active Surveillance Protocols Harbor PTEN and MYC Alterations.

BACKGROUND: Genomic characterization of prostate cancer (PCa) biopsies may improve criteria for the selection of patients suitable for active surveillance (AS). OBJECTIVE: To identify somatic genomic aberrations associated with adverse outcome as AS protocol exclusion indicators. DESIGN, SETTING AND PARTICIPANTS: Whole-exome sequencing profiles were generated for Gleason score (GS)=3+3 biopsies obtained from 54 PCa patients enrolled in two AS protocols. Patients were selected as representative of a nonindolent population, consisting of 27 patients who dropped out from AS due to upgrading (ie, finding of GS>3+3 at a follow-up biopsy) within 2 yr, and a potentially indolent population, consisting of 27 patients in AS for ≥4 yr without any evidence of reclassification. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: The genomic alteration landscape of core biopsies was analyzed using an integrated computational pipeline and correlated with patient reclassification due to upgrading. RESULTS AND LIMITATIONS: Of all the GS=3+3 biopsies of the study cohort, 34% showed clear evidence of somatic copy number aberrations along the genome. Of these, 39% came from the potentially indolent and 61% from the nonindolent population. Single-nucleotide variants demonstrated low allelic fractions and included a common F133C mutation in the SPOP gene. The minimally altered genomic landscape of the study cohort presented a distinct set of monoallelic deletions, including on 8p, 13q, 16q, and 21q, and rare amplifications of 8q, which were observed in both AS patient populations. Concerning lesions typically associated with adverse outcome, PTEN deletions and MYC amplification, though observed in a small number of cases, were detected exclusively or preferentially, respectively, in nonindolent patients. Such molecular findings were confirmed by immunohistochemistry on the same tissue blocks. The small sample size and the retrospective nature of the analysis represent the main study limitations. CONCLUSIONS: Genomic features enriched in aggressive tumors can be detected in GS=3+3 core biopsies of AS patients. PATIENT SUMMARY: PTEN and MYC alterations at the time of diagnosis would deserve investigation in larger cohorts of AS patients to assess their potential as biomarkers for a more precise/earlier identification of patients at risk of reclassification.

miR-205 enhances radiation sensitivity of prostate cancer cells by impairing DNA damage repair through PKCε and ZEB1 inhibition.

BACKGROUND: Radiotherapy is one of the main treatment options for non-metastatic prostate cancer (PCa). Although treatment technical optimization has greatly improved local tumor control, a considerable fraction of patients still experience relapse due to the development of resistance. Radioresistance is a complex and still poorly understood phenomenon involving the deregulation of a variety of signaling pathways as a consequence of several genetic and epigenetic abnormalities. In this context, cumulative evidence supports a functional role of microRNAs in affecting radioresistance, suggesting the modulation of their expression as a novel radiosensitizing approach. Here, we investigated for the first time the ability of miR-205 to enhance the radiation response of PCa models. METHODS: miR-205 reconstitution by a miRNA mimic in PCa cell lines (DU145 and PC-3) was used to elucidate miR-205 biological role. Radiation response in miRNA-reconstituted and control cells was assessed by clonogenic assay, immunofluorescence-based detection of nuclear γ-H2AX foci and comet assay. RNAi was used to silence the miRNA targets PKCε or ZEB1. In addition, target-protection experiments were carried out using a custom oligonucleotide designed to physically disrupt the pairing between the miR-205 and PKCε. For in vivo experiments, xenografts generated in SCID mice by implanting DU145 cells stably expressing miR-205 were exposed to 5-Gy single dose irradiation using an image-guided animal micro-irradiator. RESULTS: miR-205 reconstitution was able to significantly enhance the radiation response of prostate cancer cell lines and xenografts through the impairment of radiation-induced DNA damage repair, as a consequence of PKCε and ZEB1 inhibition. Indeed, phenocopy experiments based on knock-down of either PKCε or ZEB1 reproduced miR-205 radiosensitizing effect, hence confirming a functional role of both targets in the process. At the molecular level, miR-205-induced suppression of PKCε counteracted radioresistance through the impairment of EGFR nuclear translocation and the consequent DNA-PK activation. Consistently, disruption of miR-205-PKCε 3'UTR pairing almost completely abrogated the radiosensitizing effect. CONCLUSIONS: Our results uncovered the molecular and cellular mechanisms underlying the radiosensitizing effect of miR-205. These findings support the clinical interest in developing a novel therapeutic approach based on miR-205 reconstitution to increase PCa response to radiotherapy.

LEADeR role of miR-205 host gene as long noncoding RNA in prostate basal cell differentiation.

Though miR-205 function has been largely characterized, the nature of its host gene, MIR205HG, is still completely unknown. Here, we show that only lowly expressed alternatively spliced MIR205HG transcripts act as de facto pri-miRNAs, through a process that involves Drosha to prevent unfavorable splicing and directly mediate miR-205 excision. Notably, MIR205HG-specific processed transcripts revealed to be functional per se as nuclear long noncoding RNA capable of regulating differentiation of human prostate basal cells through control of the interferon pathway. At molecular level, MIR205HG directly binds the promoters of its target genes, which have an Alu element in proximity of the Interferon-Regulatory Factor (IRF) binding site, and represses their transcription likely buffering IRF1 activity, with the ultimate effect of preventing luminal differentiation. As MIR205HG functions autonomously from (albeit complementing) miR-205 in preserving the basal identity of prostate epithelial cells, it warrants reannotation as LEADeR (Long Epithelial Alu-interacting Differentiation-related RNA).

microRNAs as players and signals in the metastatic cascade: Implications for the development of novel anti-metastatic therapies.

microRNAs (miRNAs) are small non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. Increasing evidence emerging from human tumor preclinical models clearly indicates that specific miRNAs, collectively termed "metastamirs," play a functional role in different steps of the metastatic cascade, by exerting either pro- or anti-metastatic functions, and behave as signaling mediators to enable tumor cell to colonize a specific organ. miRNAs also actively participate in the proficient interaction of cancer cells with tumor microenvironment, either at the primary or at the metastatic site. Circulating miRNAs, released by multiple cell types, following binding to proteins or encapsulation in extracellular vesicles, play a main role in this cross-talk by acting as transferrable messages. The documented involvement of specific miRNAs in the dissemination process has aroused interest in the development of miRNA-based strategies for the treatment of metastasis. Preclinical research carried out in tumor experimental models, using both miRNA replacement and miRNA inhibitory approaches, is encouraging towards translating miRNA-based strategies into human cancer therapy, based on the observed therapeutic activity in the absence of main toxicity. However, to accelerate their adoption in the clinic, further improvements in terms of efficacy and targeted delivery to the tumor are still necessary.

Dissecting the role of microRNAs in prostate cancer metastasis: implications for the design of novel therapeutic approaches.

Metastatic prostate cancer is a lethal disease that remains incurable despite the recent approval of new drugs, thus making the development of alternative treatment approaches urgently needed. A more precise understanding of the molecular mechanisms underlying prostate cancer dissemination could lead to the identification of novel therapeutic targets for the design of efficient anti-metastatic strategies. MicroRNA (miRNAs) are endogenous, small non-coding RNA molecules acting as key regulators of gene expression at post-transcriptional level. It has been clearly established that altered miRNA expression is a common hallmark of cancer. In addition, emerging evidence suggests their direct involvement in the metastatic cascade. In this review, we present a comprehensive overview of the data generated in experimental tumor models indicating that specific miRNAs may impinge on the different stages of prostate cancer metastasis, including (i) the regulation of epithelial-to-mesenchymal transition and cell migration/invasion, (ii) the interplay between cancer cells and the surrounding stroma, (iii) the control of angiogenesis, (iv) the regulation of anoikis, and (v) the colonization of distant organs. Moreover, we show preliminary evidence of the clinical relevance of some of these miRNAs, in terms of association with tumor aggressiveness/dissemination and clinical outcome, as emerged from translation studies carried out in prostate cancer patient cohorts. We also discuss the potential and the current limitations of manipulating metastasis-related miRNAs, by mimicking or inhibiting them, as a strategy for the development of novel therapeutic approaches for the advanced disease.

Integrated gene and miRNA expression analysis of prostate cancer associated fibroblasts supports a prominent role for interleukin-6 in fibroblast activation.

Tumor microenvironment coevolves with and simultaneously sustains cancer progression. In prostate carcinoma (PCa), cancer associated fibroblasts (CAF) have been shown to fuel tumor development and metastasis by mutually interacting with tumor cells. Molecular mechanisms leading to activation of CAFs from tissue-resident fibroblasts, circulating bone marrow-derived fibroblast progenitors or mesenchymal stem cells are largely unknown. Through integrated gene and microRNA expression profiling, we showed that PCa-derived CAF transcriptome strictly resembles that of normal fibroblasts stimulated in vitro with interleukin-6 (IL6), thus proving evidence, for the first time, that the cytokine is able per se to induce most of the transcriptional changes characteristic of patient-derived CAFs. Comparison with publicly available datasets, however, suggested that prostate CAFs may be alternatively characterized by IL6 and TGFß-related signatures, indicating that either signal, depending on the context, may concur to fibroblast activation. Our analyses also highlighted novel pathways potentially relevant for induction of a reactive stroma. In addition, we revealed a role for muscle-specific miR-133b as a soluble factor secreted by activated fibroblasts to support paracrine activation of non-activated fibroblasts or promote tumor progression.Overall, we provided insights into the molecular mechanisms driving fibroblast activation in PCa, thus contributing to identify novel hits for the development of therapeutic strategies targeting the crucial interplay between tumor cells and their microenvironment.

Anti-tumor activity of selective inhibitors of XPO1/CRM1-mediated nuclear export in diffuse malignant peritoneal mesothelioma: the role of survivin.

Survivin, which is highly expressed and promotes cell survival in diffuse malignant peritoneal mesothelioma (DMPM), exclusively relies on exportin 1 (XPO1/CRM1) to be shuttled into the cytoplasm and perform its anti-apoptotic function. Here, we explored the efficacy of Selective Inhibitors of Nuclear Export (SINE), KPT-251, KPT-276 and the orally available, clinical stage KPT-330 (selinexor), in DMPM preclinical models. Exposure to SINE induced dose-dependent inhibition of cell growth, cell cycle arrest at G1-phase and caspase-dependent apoptosis, which were consequent to a decrease of XPO1/CRM1 protein levels and the concomitant nuclear accumulation of its cargo proteins p53 and CDKN1a. Cell exposure to SINE led to a time-dependent reduction of cytoplasmic survivin levels. In addition, after an initial accumulation, the nuclear protein abundance progressively decreased, as a consequence of an enhanced ubiquitination and proteasome-dependent degradation. SINE and the survivin inhibitor YM155 synergistically cooperated in reducing DMPM cell proliferation. Most importantly, orally administered SINE caused a significant anti-tumor effect in subcutaneous and orthotopic DMPM xenografts without appreciable toxicity. Overall, we have demonstrated a marked efficacy of SINE in DMPM preclinical models that may relay on the interference with survivin intracellular distribution and function. Our study suggests SINE-mediated XPO1/CRM1 inhibition as a novel therapeutic option for DMPM.

Targeting microRNAs to withstand cancer metastasis.

MicroRNAs are endogenous, regulatory, noncoding small RNAs shown to play a key role in controlling gene expression, mainly at the posttranscriptional level. Several lines of evidence highlighted the importance of selected microRNAs as essential actors of cancer initiation events, tumor progression towards malignancy, and ultimately metastasis. By acting as either prometastatic or antimetastatic factors, microRNAs may represent novel targets or tools to withstand cancer progression. This chapter summarizes the available strategies to manipulate the expression of metastasis-related microRNAs, either by mimicking or inhibiting them, in cell systems and in vivo models. In addition, we provide a broad overview of conceptual and technological issues that need to be addressed before microRNAs might be exploited in the clinical setting for the prevention and treatment of the metastatic disease.

Novel 1H-pyrrolo[2,3-b]pyridine derivative nortopsentin analogues: synthesis and antitumor activity in peritoneal mesothelioma experimental models.

In this study, we describe the synthesis of new nortopsentin analogues, 1H-pyrrolo[2,3-b]pyridine derivatives and their biological effects in experimental models of diffuse malignant peritoneal mesothelioma (DMPM), a rare and rapidly fatal disease, poorly responsive to conventional therapies. The three most active compounds, 1f (3-[2-(5-fluoro-1-methyl-1H-indol-3-yl)-1,3-thiazol-4-yl]-1H-pyrrolo[2,3-b]pyridine), 3f (3-[2-(1H-indol-3-yl)-1,3-thiazol-4-yl]-1-methyl-1H-pyrrolo[2,3-b]pyridine), and 1l (3-[2-(5-fluoro-1-methyl-1H-indol-3-yl)-1,3-thiazol-4-yl]-1-methyl-1H-pyrrolo[2,3-b] pyridine), which were shown to act as cyclin-dependent kinase 1 inhibitors, consistently reduced DMPM cell proliferation and induced a caspase-dependent apoptotic response, with a concomitant reduction of the expression of the active Thr(34)-phosphorylated form of the antiapoptotic protein survivin. Moreover, the combined treatment of DMPM cells with 3f derivative and paclitaxel produced a synergistic cytotoxic effect, which was paralleled by an enhanced apoptotic response. In the mouse model, i.p. administration of 1f, 3f, and 1l derivatives was effective, resulting in a significant tumor volume inhibition of DMPM xenografts (range, 58-75%) at well-tolerated doses, and two complete responses were observed in each treatment group.