Residual breast cancer metabolic phenotype after docetaxel treatment

Despite improvements in early diagnosis and prevention, late stage breast cancer is often incurable due to metastasis, tumour relapse, resistance and incomplete response to treatments. Metabolic reprogramming has been recognised as a critical element for cancer cells to grow under hostile conditions and this is likely to contribute towards resistance against chemotherapeutics. This thesis therefore aimed at deciphering the metabolic phenotype of residual breast cancer which survived docetaxel treatment, $in$ $vitro$ and $in$ $vivo$, quantifying polar metabolite levels and conducting pathway tracing and metabolic flux analysis using stable isotope ($^{13}$C) labelled tracers. $In$ $vitro$ residual cells presented a hypermetabolic phenotype characterised by significant accumulation of essential and non-essential amino acids, together with an elicited Warburg effect and an increased antioxidant response based on glutathione production, while in growth arrest. A method to carry out $in$ $vivo$ tracer-based metabolic studies was successfully developed using a breast cancer mouse model. Although the metabolite accumulation outlined $in$ $vitro$ was not observed $in$ $vivo$, a protective phenotype against oxidative stress was supported by increased flux through the oxidative branch of the pentose phosphate pathway. In conclusion, this thesis demonstrated that metabolic phenotyping is a valid approach to uncover key metabolic alterations in residual tumours both $in$ $vitro$ and $in$ $vivo$, and could be further exploited to design personalised treatments aimed at restoring sensitivity to therapies

Modeling of Intracellular Taurine Levels Associated with Ovarian Cancer Reveals Activation of p53, ERK, mTOR and DNA-Damage-Sensing-Dependent Cell Protection

Taurine, a non-proteogenic amino acid and commonly used nutritional supplement, can protect various tissues from degeneration associated with the action of the DNA-damaging chemotherapeutic agent cisplatin. Whether and how taurine protects human ovarian cancer (OC) cells from DNA damage caused by cisplatin is not well understood. We found that OC ascites-derived cells contained significantly more intracellular taurine than cell culture-modeled OC. In culture, elevation of intracellular taurine concentration to OC ascites-cell-associated levels suppressed proliferation of various OC cell lines and patient-derived organoids, reduced glycolysis, and induced cell protection from cisplatin. Taurine cell protection was associated with decreased DNA damage in response to cisplatin. A combination of RNA sequencing, reverse-phase protein arrays, live-cell microscopy, flow cytometry, and biochemical validation experiments provided evidence for taurine-mediated induction of mutant or wild-type p53 binding to DNA, activation of p53 effectors involved in negative regulation of the cell cycle (p21), and glycolysis (TIGAR). Paradoxically, taurine’s suppression of cell proliferation was associated with activation of pro-mitogenic signal transduction including ERK, mTOR, and increased mRNA expression of major DNA damage-sensing molecules such as DNAPK, ATM and ATR. While inhibition of ERK or p53 did not interfere with taurine’s ability to protect cells from cisplatin, suppression of mTOR with Torin2, a clinically relevant inhibitor that also targets DNAPK and ATM/ATR, broke taurine’s cell protection. Our studies implicate that elevation of intracellular taurine could suppress cell growth and metabolism, and activate cell protective mechanisms involving mTOR and DNA damage-sensing signal transduction

Cancer Stem Cells: Devil or Savior—Looking behind the Scenes of Immunotherapy Failure

Although the introduction of immunotherapy has tremendously improved the prognosis of patients with metastatic cancers of different histological origins, some tumors fail to respond or develop resistance. Broadening the clinical efficacy of currently available immunotherapy strategies requires an improved understanding of the biological mechanisms underlying cancer immune escape. Globally, tumor cells evade immune attack using two main strategies: avoiding recognition by immune cells and instigating an immunosuppressive tumor microenvironment. Emerging data suggest that the clinical efficacy of chemotherapy or molecularly targeted therapy is related to the ability of these therapies to target cancer stem cells (CSCs). However, little is known about the role of CSCs in mediating tumor resistance to immunotherapy. Due to their immunomodulating features and plasticity, CSCs can be especially proficient at evading immune surveillance, thus potentially representing the most prominent malignant cell component implicated in primary or acquired resistance to immunotherapy. The identification of immunomodulatory properties of CSCs that include mechanisms that regulate their interactions with immune cells, such as bidirectional release of particular cytokines/chemokines, fusion of CSCs with fusogenic stromal cells, and cell-to-cell communication exerted by extracellular vesicles, may significantly improve the efficacy of current immunotherapy strategies. The purpose of this review is to discuss the current scientific evidence linking CSC biological, immunological, and epigenetic features to tumor resistance to immunotherapy