Regulation of receptor tyrosine kinases by miRNA: overexpression of miRNA using lentiviral inducible expression vectors

Development of a rational strategy for integration of lactate dehydrogenase A suppression into therapeutic algorithms for head and neck cancer

BACKGROUND

Lactate dehydrogenase (LDH) is a critical metabolic enzyme. LDH A (LDHA) overexpression is a hallmark of aggressive malignancies and has been linked to tumour initiation, reprogramming and progression in multiple tumour types. However, successful LDHA inhibition strategies have not materialised in the translational and clinical space. We sought to develop a rational strategy for LDHA suppression in the context of solid tumour treatment.

METHODS

We utilised a doxycycline-inducible short hairpin RNA (shRNA) system to generate LDHA suppression. Lactate and LDH activity levels were measured biochemically and kinetically using hyperpolarised 13C-pyruvate nuclear magnetic resonance spectroscopy. We evaluated effects of LDHA suppression on cellular proliferation and clonogenic survival, as well as on tumour growth, in orthotopic models of anaplastic thyroid carcinoma (ATC) and head and neck squamous cell carcinoma (HNSCC), alone or in combination with radiation.

RESULTS

shRNA suppression of LDHA generated a time-dependent decrease in LDH activity with transient shifts in intracellular lactate levels, a decrease in carbon flux from pyruvate into lactate and compensatory shifts in metabolic flux in glycolysis and the Krebs cycle. LDHA suppression decreased cellular proliferation and temporarily stunted tumour growth in ATC and HNSCC xenografts but did not by itself result in tumour cure, owing to the maintenance of residual viable cells. Only when chronic LDHA suppression was combined with radiation was a functional cure achieved.

CONCLUSIONS

Successful targeting of LDHA requires exquisite dose and temporal control without significant concomitant off-target toxicity. Combinatorial strategies with conventional radiation are feasible as long as the suppression is targeted, prolonged and non-toxic.

RTKs in pathobiology of head and neck cancers

Non-communicable diseases contribute to 71% of the deaths worldwide, of which cancers rank second after cardiovascular diseases. Among all the cancers, head and neck cancers (HNC) are consequential in augmenting the global cancer incidence as well as mortality. Receptor tyrosine kinases (RTKs) are emphatic for the matter that they serve as biomarkers aiding the analysis of tumor progression and metastasis as well as diagnosis, prognosis and therapeutic progression in the patients. The extensive researches on HNC have made significant furtherance in numerous targeted therapies, but for the escalating therapeutic resistance. This review explicates RTKs in HNC, their signaling pathways involved in tumorigenesis, metastasis and stemness induction, the association of non-coding RNAs with RTKs, an overview of RTK based therapy and associated resistance in HNC, as well as a sneak peek into the HPV positive HNC and its therapy. The review extrapolates the cardinal role of RTKs and RTK based therapy as superior to other existing therapeutic interventions for HNC.

Reciprocal regulation of γ-globin expression by exo-miRNAs: Relevance to γ-globin silencing in β-thalassemia major

Induction of fetal hemoglobin (HbF) is a promising strategy in the treatment of β-thalassemia major (β-TM). The present study shows that plasma exosomal miRNAs (exo-miRs) are involved in γ-globin regulation. Exosomes shuttle miRNAs and mediate cell-cell communication. MiRNAs are regulators of biological processes through post-transcriptional targeting. Compared to HD (Healthy Donor), β-TM patients showed increased levels of plasma exosomes and the majority of exosomes had cellular origin from CD34+ cells. Further, HD and β-TM exosomes showed differential miRNA expressions. Among them, deregulated miR-223-3p and miR-138-5p in β-TM exosomes and HD had specific targets for γ-globin regulator and repressor respectively. Functional studies in K562 cells showed that HD exosomes and miR-138-5p regulated γ-globin expression by targeting BCL11A. β-TM exosomes and miR-223-3p down regulated γ-globin expression through LMO2 targeting. Importantly, miR-223-3p targeting through sponge repression resulted in γ-globin activation. Further, hnRNPA1 bound to stem-loop structure of pre-miR-223 and we found that hnRNPA1 knockdown or mutagenesis at miR-223-3p stem-loop sequence resulted in less mature exo-miR-223-3p levels. Altogether, the study shows for the first time on the important clinical evidence that differentially expressed exo-miRNAs reciprocally control γ-globin expressions. Further, the hnRNPA1-exo-miR-223-LMO2 axis may be critical to γ-globin silencing in β-TM.