Hsp70 inhibition induces myeloma cell death via the intracellular accumulation of immunoglobulin and the generation of proteotoxic stress.

Multiple myeloma (MM) cells rely on protein homeostatic mechanisms for survival. These mechanisms could be therapeutically targeted via modulation of the heat shock response. We studied the roles of Hsp72 and Hsc70, and show that the two major cytoplasmic Hsp70s play a key role in regulating protein homeostasis and controlling multiple oncogenic pathways in MM, and their inhibition can lead to myeloma cell death. Our study provides further evidence that targeting Hsp70 represents a novel therapeutic approach which may be effective in the treatment of MM.

Characterization of a novel mouse model of multiple myeloma and its use in preclinical therapeutic assessment.

To aid preclinical development of novel therapeutics for myeloma, an in vivo model which recapitulates the human condition is required. An important feature of such a model is the interaction of myeloma cells with the bone marrow microenvironment, as this interaction modulates tumour activity and protects against drug-induced apoptosis. Therefore NOD/SCIDγc(null) mice were injected intra-tibially with luciferase-tagged myeloma cells. Disease progression was monitored by weekly bioluminescent imaging (BLI) and measurement of paraprotein levels. Results were compared with magnetic resonance imaging (MRI) and histology. Assessment of model suitability for preclinical drug testing was investigated using bortezomib, melphalan and two novel agents. Cells engrafted at week 3, with a significant increase in BLI radiance occurring between weeks 5 and 7. This was accompanied by an increase in paraprotein secretion, MRI-derived tumour volume and CD138 positive cells within the bone marrow. Treatment with known anti-myeloma agents or novel agents significantly attenuated the increase in all disease markers. In addition, intra-tibial implantation of primary patient plasma cells resulted in development of myeloma within bone marrow. In conclusion, using both myeloma cell lines and primary patient cells, we have developed a model which recapitulates human myeloma by ensuring the key interaction of tumour cells with the microenvironment.

Mechanisms underlying gemcitabine resistance in pancreatic cancer and sensitisation by the iMiD™ lenalidomide.

Gemcitabine is currently the leading therapeutic for pancreatic cancer treatment, despite growing resistance. Studying the mechanisms that underlie gemcitabine resistance and discovery of agents that increase the tumour sensitivity to gemcitabine, is therefore desirable. The thalidomide analogue lenalidomide has been approved for use in multiple myeloma in combination with dexamethasone. Although it is primarily immunomodulatory, it also has direct effects on tumours. We investigated the sensitivity of three pancreatic cell lines PANC-1, MIA-PaCa-2 and BxPC-3 to gemcitabine. We observed that PANC-1 cells display most resistance to gemcitabine and MIA-PaCa-2 are most sensitive. Western blot analysis revealed that PANC-1 exhibits high phosphorylated extracellular signal-regulated kinase (pERK) expression, whereas MIA-PaCa-2 displays low expression. Combining gemcitabine and lenalidomide reduced the IC(50) of gemcitabine up to 40% (p<0.05). Western blot analysis showed lenalidomide significantly reduced pERK expression in all cell lines (p<0.05). It was hypothesised that gemcitabine sensitivity could be increased through combination with a pERK-reducing agent. The mitogen-activated kinase (MEK) specific inhibitor U0126 was used on PANC-1 cells to restore gemcitabine sensitivity. U0126 significantly increased cell killing by gemcitabine from 30% to 60% (p<0.001). Sensitive MIA-PaCa-2 cells were transfected with a constitutively active MEK mutant to reduce gemcitabine sensitivity. Transfection resulted in a significant reduction in cell killing by gemcitabine from 54-16% (p<0.05). These results provide evidence that ERK activity underlies sensitivity to gemcitabine and that addition of an agent that reduces this activity, such as lenalidomide, enhances gemcitabine efficacy. In conclusion, these results provide an understanding of gemcitabine resistance and could be used to predict successful combination therapies.

Recent advances and developments in treatment strategies against pancreatic cancer.

Recent years have seen improvements in strategies to treat pancreatic cancer. Pancreatic cancer is a leading cause of cancer-related death in the world, and is characterised by rapid disease progression, highly invasive tumour phenotype and resistance to chemotherapy. Patient prognosis is extremely grim, with a one-year survival rate of just 10% and only a 5% chance of surviving beyond five years. There has been little change in the treatment regimen, with 5-FU-based therapies being the usual route. Gemcitabine has also offered some relief over the past two decades, with modest improvements in median survival. This lack of choice has increased the call for new treatments, and indeed, novel drugs are now being investigated for their use in pancreatic cancer. These include those agents classically applied to other indications such as doxycycline and doxorubicin, as well as dietary components such as curcumin and genistein. Each of these drugs possesses different levels of activity both as single agents and in combinatorial approaches with gemcitabine. This review will discuss the difficulties in treating pancreatic cancer, and will summarise the progress and latest development in drugs used within this field of cancer.