The therapeutic target Hsp90 and cancer hallmarks

Association of Hsp90 with p53 and Fizzy related homolog (Fzr) synchronizing Anaphase Promoting Complex (APC/C): An unexplored ally towards oncogenic pathway

The intricate molecular interactions leading to the oncogenic pathway are the consequence of cell cycle modification controlled by a bunch of cell cycle regulatory proteins. The tumor suppressor and cell cycle regulatory proteins work in coordination to maintain a healthy cellular environment. The integrity of this cellular protein pool is perpetuated by heat shock proteins/chaperones, which assist in proper protein folding during normal and cellular stress conditions. Among these versatile groups of chaperone proteins, Hsp90 is one of the significant ATP-dependent chaperones that aid in stabilizing many tumor suppressors and cell cycle regulator protein targets. Recently, studies have revealed that in cancerous cell lines, Hsp90 stabilizes mutant p53, 'the guardian of the genome.' Hsp90 also has a significant impact on Fzr, an essential regulator of the cell cycle having an important role in the developmental process of various organisms, including Drosophila, yeast, Caenorhabditis elegans, and plants. During cell cycle progression, p53 and Fzr coordinately regulate the Anaphase Promoting Complex (APC/C) from metaphase to anaphase transition up to cell cycle exit. APC/C mediates proper centrosome function in the dividing cell. The centrosome acts as the microtubule organizing center for the correct segregation of the sister chromatids to ensure perfect cell division. This review examines the structure of Hsp90 and its co-chaperones, which work in synergy to stabilize proteins such as p53 and Fizzy-related homolog (Fzr) to synchronize the Anaphase Promoting Complex (APC/C). Dysfunction of this process activates the oncogenic pathway leading to the development of cancer. Additionally, an overview of current drugs targeting Hsp90 at various phases of clinical trials has been included.

Linking hsp90's role as an evolutionary capacitator to the development of cancer

This paper links Heat Shock Protein Hsp90 as an evolutionary capacitator with the development of cancer. Hsp90 stabilises proteins associated with cancer in a number of ways. Canalisation allows for the accumulation of malignant mutations in the genome, and selection of beneficial phenotypes when cancer cells are stressed, allowing oncogenic development and progression. Hsp90 may allow for mutational 'big bangs' that can trigger primary malignant transformation. Hsp90 buffers catastrophic mutations in the oncogenome to prevent protein degradation and cellular apoptosis. Hsp90 was found to prevent the degradation of mutated p53, encouraging uncontrolled proliferation of cancer cells. Hsp90 buffering of mutations in response to cytotoxic therapy can lead to expression of beneficial phenotypes when Hsp90 is supressed and development of drug resistance. Trials with Hsp90 inhibitors have shown some success as an adjunctive therapy in preventing cancer progression, development of drug resistance, and even re-sensitisation to therapy after chemoresistance has developed.

From Bacteria to Cancer: A Benzothiazole-Based DNA Gyrase B Inhibitor Redesigned for Hsp90 C-Terminal Inhibition

Heat shock protein 90 (Hsp90) is a molecular chaperone that is responsible for the folding and maturation of client proteins that are associated with all ten hallmarks of cancer. Hsp90 N-terminal pan inhibitors have experienced unfavorable results in clinical trials due to induction of the heat shock response (HSR), among other concerns. Novobiocin, a well characterized DNA gyrase B inhibitor, was identified as the first Hsp90 C-terminal inhibitor that manifested anticancer effects without induction of the HSR. In this letter, a library of Hsp90 C-terminal inhibitors derived from a benzothiazole-based scaffold, known to inhibit DNA gyrase B, was designed, synthesized, and evaluated. Several compounds were found to manifest low micromolar activity against both MCF-7 and SKBr3 breast cancer cell lines via Hsp90 C-terminal inhibition.

Misfolded proteins: from little villains to little helpers in the fight against cancer

The application of cytostatic drugs targeting the high proliferation rates of cancer cells is currently the most commonly used treatment option in cancer chemotherapy. However, severe side effects and resistance mechanisms may occur as a result of such treatment, possibly limiting the therapeutic efficacy of these agents. In recent years, several therapeutic strategies have been developed that aim at targeting not the genomic integrity and replication machinery of cancer cells but instead their protein homeostasis. During malignant transformation, the cancer cell proteome develops vast aberrations in the expression of mutated proteins, oncoproteins, drug- and apoptosis-resistance proteins, etc. A complex network of protein quality-control mechanisms, including chaperoning by heat shock proteins (HSPs), not only is essential for maintaining the extravagant proteomic lifestyle of cancer cells but also represents an ideal cancer-specific target to be tackled. Furthermore, the high rate of protein synthesis and turnover in certain types of cancer cells can be specifically directed by interfering with the proteasomal and autophagosomal protein recycling and degradation machinery, as evidenced by the clinical application of proteasome inhibitors. Since proteins with loss of their native conformation are prone to unspecific aggregations and have proved to be detrimental to normal cellular function, specific induction of misfolded proteins by HSP inhibitors, proteasome inhibitors, hyperthermia, or inducers of endoplasmic reticulum stress represents a new method of cancer cell killing exploitable for therapeutic purposes. This review describes drugs - approved, repurposed, or under investigation - that can be used to accumulate misfolded proteins in cancer cells, and particularly focuses on the molecular aspects that lead to the cytotoxicity of misfolded proteins in cancer cells.

Tumour suppressor HLJ1: A potential diagnostic, preventive and therapeutic target in non-small cell lung cancer

Lung cancer is the leading cause of cancer-related mortality throughout the world. Non-small cell lung cancer (NSCLC) accounts for 85% of all diagnosed lung cancers. Despite considerable progress in the diagnosis and treatment of the disease, the overall 5-year survival rate of NSCLC patients remains lower than 15%. The most common causes of death in lung cancer patients are treatment failure and metastasis. Therefore, developing novel strategies that target both tumour growth and metastasis is an important and urgent mission for the next generation of anticancer therapy research. Heat shock proteins (HSPs), which are involved in the fundamental defence mechanism for maintaining cellular viability, are markedly activated during environmental or pathogenic stress. HSPs facilitate rapid cell division, metastasis, and the evasion of apoptosis in cancer development. These proteins are essential players in the development of cancer and are prime therapeutic targets. In this review, we focus on the current understanding of the molecular mechanisms responsible for HLJ1’s role in lung cancer carcinogenesis and progression. HLJ1, a member of the human HSP 40 family, has been characterised as a tumour suppressor. Research studies have also reported that HLJ1 shows promising dual anticancer effects, inhibiting both tumour growth and metastasis in NSCLC. The accumulated evidence suggests that HLJ1 is a potential biomarker and treatment target for NSCLC.

Aplysin induces apoptosis in glioma cells through HSP90/AKT pathway

Glioma is one of the most common malignancies in the world. However, an effective regiment is lacking. Increasing evidence indicated that PI3K/AKT signaling is critical for the survival of glioma. In this study, we aimed to study the effect of aplysin on the survival and proliferation of GL26 glioma cells and the involved mechanisms. The data showed that aplysin suppressed the viability of glioma cells in both dose- and time-dependent manners. It also induced G0/G1 arrest and apoptosis in glioma cells. Western blot assays revealed that aplysin treatment changed p-AKT expression by impairing the formation of Heat shock protein 90/AKT complex. Aplysin significantly increased the survival time of mice-bearing glioma and reduced the weights of the established gliomas. Collectively, aplysin can inhibit the proliferation of GL26 glioma cells and induce apoptosis in vitro, perhaps through suppressing PI3K/AKT pathway. It can also inhibit glioma growth in vivo and prolong the survival of mice. Thus, aplysin may be a novel therapeutic drug for glioma.