Mechanisms of cisplatin resistance and targeting of cancer stem cells: Adding glycosylation to the equation

Cisplatin-based chemotherapeutic regimens are the most frequently used (neo)adjuvant treatments for the majority of solid tumors. While platinum-based chemotherapeutic regimens have proven effective against highly proliferative malignant tumors, significant relapse and progression rates as well as decreased overall survival are still observed. Currently, it is known that sub-populations of chemoresistant cells share biological properties with cancer stem cells (CSC), which are believed to be responsible for tumor relapse, invasion and ultimately disease dissemination through acquisition of mesenchymal cell traits. In spite of concentrated efforts devoted to decipher the mechanisms underlying CSC chemoresistance and to design targeted therapeutics to these cells, proteomics has failed to unveil molecular signatures capable of distinguishing between malignant and non-malignant stem cells. This has hampered substantial developments in this complex field. Envisaging a novel rationale for an effective therapy, the current review summarizes the main cellular and molecular mechanisms underlying cisplatin resistance and the impact of chemotherapy challenge in CSC selection and clinical outcome. It further emphasizes the growing amount of data supporting a role for protein glycosylation in drug resistance. The dynamic and context-dependent nature of protein glycosylation is also comprehensively discussed, hence highlighting its potentially important role as a biomarker of CSC. As the paradigm of cancer therapeutics shifts towards precision medicine and patient-tailored therapeutics, we bring into focus the need to introduce glycomics and glycoproteomics in holistic pan-omics models, in order to integrate diverse, multimodal and clinically relevant information towards more effective cancer therapeutics.This work was supported by European Union funds (FEDER/COMPETE) and by national funds (FCT, the Portuguese Foundation for Science and Technology) under the projects with the references FCOMP-01-0124-FEDER 028188 (PTDC/BBB-EBI/0786/2012) and PTDC/BBB-EBI/0567/2014. C.R. acknowledges the support by Gastric Glyco Explorer Initial Training Network (Seventh Framework Programme grant no. 316929). IPATIMUP integrates the i3S Research Unit, which is partially supported by FCT, (PEst-C/SAU/LA0003/2013). Grants were received from FCT: SFRH/BPD/111048/2015 to J.A.F and SFRH/BD/111242/2015 to A.P. FCT is co-financed by European Social Fund (ESF) under Human Potential Operation Programme (POPH) from National Strategic Reference Framework (NSRF)

Investigating the role of microRNA-31 as a modulator of chemosensitivity in malignant leural mesothelioma

Malignant pleural mesothelioma (MPM) is associated with an extremely poor prognosis and the majority of patients are initially or rapidly become unresponsive to platinum-based chemotherapy. MicroRNA-31 (miR-31) is encoded on a genomic fragile site, 9p21.3, which is reportedly lost in approximately half of MPM tumours, and its prognostic value is currently ambiguous. Based on previous findings in a variety of other cancers, it was hypothesised that miR-31 loss confers chemoresistance and that miR-31 reconstitution may enhance sensitivity to chemotherapeutics in MPM. Surprisingly, reintroduction of miR-31 into epithelioid miR-31-null NCI-H2452 cells significantly enhanced clonogenic resistance to cisplatin and carboplatin. Conversely, suppression of endogenous miR-31 in P31 epithelioid cells significantly increased chemosensitivity. Interestingly, while miR-31 overexpression increased resistance to platinum-containing therapeutics, paradoxically, a higher relative intracellular concentration of platinum was observed versus controls. While the expression of the drug influx transporter CTR1 was increased upon miR-31 re-expression, a significantly decreased intranuclear concentration of platinum was observed, with associated reduction in DNA damage, potentially explaining the increase in cisplatin accumulation but decreased chemosensitivity. The converse relationship was demonstrated in P31 cells upon endogenous miR-31 suppression, further suggesting a mechanism underpinning resistance that involves altered nuclear transport. Linked with a downregulation of OCT1, a bipotential transcriptional regulator with multiple miR-31 target binding sites, we subsequently identified an indirect miR-31-mediated upregulation of ABCB9, a transporter associated with drug accumulation in lysosomes, and increased uptake of platinum to lysosomes. However, when overexpressed directly, ABCB9 promoted cellular chemosensitivity, suggesting the miR-31 promotes chemoresistance largely via an ABCB9-independent mechanism. Overall, these data suggest that miR-31 loss from MPM tumours does not promote chemoresistance in MPM, and may be prognostically beneficial in the context of therapeutic sensitivity. As such, endogenous miR-31 suppression may actually enhance sensitivity to platinum-based treatment in patients with MPM

(In)Distinctive Role of Long Non-Coding RNAs in Common and Rare Ovarian Cancers

Simple Summary:& nbsp;Ovarian cancers (OCs) are the most lethal form of gynecological tumors. The commonest are high-grade serous OCs, while rare OCs originate from many different cell types, such as epithelial, germ cell, sex cord-stromal, or mixed types. Rare OCs have distinct molecular characteristics, prognosis, and therapeutic approaches. However, all ovarian malignancies mostly share the same problem: late diagnosis due to the lack of specific symptoms. Therefore, there is a perpetual need to discover better diagnostic, prognostic, and predictive biomarkers, as well as new therapeutic approaches. In recent years, long non-coding RNAs (lncRNAs) have gained widespread attention because of their important role in various biological pathways. They have multiple mechanisms of action with an important role in many cellular processes related to OCs development and progression. This review will focus on the different aspects of lncRNAs in OCs and attempt to highlight the distinctive role of lncRNAs in common and rare OCs

Epithelial Ovarian Cancer

Epithelial ovarian cancer generally presents at an advanced stage and is the most common cause of gynaecological cancer death. Treatment requires expert multidisciplinary care. Population-based screening has been ineffective, but new approaches for early diagnosis and prevention that leverage molecular genomics are in development. Initial therapy includes surgery and adjuvant therapy. Epithelial ovarian cancer is composed of distinct histological subtypes with unique genomic characteristics, which are improving the precision and effectiveness of therapy, allowing discovery of predictors of response such as mutations in breast cancer susceptibility genes BRCA1 and BRCA2, and homologous recombination deficiency for DNA damage response pathway inhibitors or resistance (cyclin E1). Rapidly evolving techniques to measure genomic changes in tumour and blood allow for assessment of sensitivity and emergence of resistance to therapy, and might be accurate indicators of residual disease. Recurrence is usually incurable, and patient symptom control and quality of life are key considerations at this stage. Treatments for recurrence have to be designed from a patient's perspective and incorporate meaningful measures of benefit. Urgent progress is needed to develop evidence and consensus-based treatment guidelines for each subgroup, and requires close international cooperation in conducting clinical trials through academic research groups such as the Gynecologic Cancer Intergroup.status: publishe

TARGETING THE WNT PATHWAY IN OVARIAN CANCER DISSEMINATION

Master'sMASTER OF SCIENC

Not only P-glycoprotein: amplification of the ABCB1-containing chromosome region 7q21 confers multidrug resistance upon cancer cells by coordinated overexpression of an assortment of resistance-related proteins

The development of drug resistance continues to be a dominant hindrance toward curative cancer treatment. Overexpression of a wide-spectrum of ATP-dependent efflux pumps, and in particular of ABCB1 (P-glycoprotein or MDR1) is a well-known resistance mechanism for a plethora of cancer chemotherapeutics including for example taxenes, anthracyclines, Vinca alkaloids, and epipodopyllotoxins, demonstrated by a large array of published papers, both in tumor cell lines and in a variety of tumors, including various solid tumors and hematological malignancies. Upon repeated or even single dose treatment of cultured tumor cells or tumors in vivo with anti-tumor agents such as paclitaxel and doxorubicin, increased ABCB1 copy number has been demonstrated, resulting from chromosomal amplification events at 7q11.2-21 locus, leading to marked P-glycoprotein overexpression, and multidrug resistance (MDR). Clearly however, additional mechanisms such as single nucleotide polymorphisms (SNPs) and epigenetic modifications have shown a role in the overexpression of ABCB1 and of other MDR efflux pumps. However, notwithstanding the design of 4 generations of ABCB1 inhibitors and the wealth of information on the biochemistry and substrate specificity of ABC transporters, translation of this vast knowledge from the bench to the bedside has proven to be unexpectedly difficult. Many studies show that upon repeated treatment schedules of cell cultures or tumors with taxenes and anthracyclines as well as other chemotherapeutic drugs, amplification, and/or overexpression of a series of genes genomically surrounding the ABCB1 locus, is observed. Consequently, altered levels of other proteins may contribute to the establishment of the MDR phenotype, and lead to poor clinical outcome. Thus, the genes contained in this ABCB1 amplicon including ABCB4, SRI, DBF4, TMEM243, and RUNDC3B are overexpressed in many cancers, and especially in MDR tumors, while TP53TG1 and DMTF1 are bona fide tumor suppressors. This review describes the role of these genes in cancer and especially in the acquisition of MDR, elucidates possible connections in transcriptional regulation (co-amplification/repression) of genes belonging to the same ABCB1 amplicon region, and delineates their novel emerging contributions to tumor biology and possible strategies to overcome cancer MDR

TP63 is implicated in apoptotic dysregulation in melanoma

PhDCutaneous melanoma is an aggressive malignancy accounting for 4% of skin cancers but 80% of all skin-cancer related deaths. Its incidence is rapidly rising and advanced disease is notoriously treatment-resistant. The role of apoptosis in melanoma pathogenesis and chemoresistance is poorly characterised. Mutations in TP53 occur infrequently and are not critical for tumour development, yet the TP53 apoptotic pathway is abrogated; this may alternatively result from TP53 pathway defects or from alterations in other members of the TP53 family, including the TP53 homologue, TP63. The hypothesis of this thesis was that TP63 has an anti-apoptotic role in melanoma and is responsible for mediating chemoresistance. The primary aims were to investigate the biological role of TP63 in melanoma, to explore regulation of p63 expression and to understand its role in apoptosis and dysregulation of the TP53 apoptotic pathway in melanoma. Although p63 was not expressed in primary melanocytes, upregulation of both p63 mRNA and protein was observed in melanoma cell lines and tissue samples. This is the first report of significant p63 expression in this lineage. Furthermore, aberrant cytoplasmic p63 expression significantly correlated with poor overall outcome in melanoma patients. Multiple possible mechanisms were demonstrated to regulate TP63 expression in melanoma, including epigenetic modulation, microRNA regulation of gene transcription and proteosome-dependent stability of p63 protein. In response to genotoxic stress, endogenous p63 isoforms were stabilised in both nuclear and mitochondrial subcellular compartments. Translocation of p63 to the mitochondria occurred through a co-dependent process with p53 but accumulation of wt-p53 in the nucleus was inhibited by p63. Using RNAi technology, both isoforms of p63 (TA and ΔNp63) were demonstrated to confer chemoresistance in melanoma. In addition, the truncated variant, ΔNp63, was enriched in a subset of melanomas expressing CD133, pointing to an anti-apoptotic role for p63 in putative cancer stem cells in this aggressive tumour. Taken together, these data suggest that in melanoma, p63 is an oncogene which contributes to dysregulation of wt-p53 function and has an important role in mediating chemoresistance. Ultimately, these observations may provide the rationale for novel approaches aimed at sensitising advanced melanoma to chemotherapeutic agents

Circadian Clock Disruption Improves the Efficacy of Chemotherapy Through p73-Mediated Apoptosis

The circadian clock in mammalian organisms is generated by a transcription-translation feedback loop (TTFL) which controls many biochemical pathways at the cellular level and physiology and behavior at the organismal level. Cryptochrome (Cry) is a key protein in the negative arm of the TTFL. It has been found that Cry mutation in cells with p53-null genotype increased their sensitivity to apoptosis by genotoxic agents. Here, I show that this increased sensitivity is due to upregulation of the p53 gene family member p73 in response to DNA damage. As a consequence, when tumors arising from oncogenic Ras-transformed p53-/- and p53-/-Cry1-/-Cry2-/- cells are treated with the anticancer drug, oxaliplatin, the p53-/- tumors continue to grow whereas the p53-/-Cry1-/-Cry2-/- tumors exhibit extensive apoptosis and stop growing. This finding provides a mechanistic foundation for overcoming the resistance of p53-deficient tumor cells to apoptosis induced by DNA-damaging agents and suggests that disruption of cryptochrome function may increase the sensitivity of tumors with p53 mutation to chemotherapy