Prolyl hydroxylase and hypoxia inducible factor: potential targets for cancer therapy

Collagen prolyl hydroxylase 3 has a tumor suppressive activity in human lung cancer

Collagen prolyl hydroxylases (P3H) are required for proper collagen biosynthesis. One of the family members P3H3 was downregulated in breast cancer and lymphoma due to DNA methylation. However the role of P3H3 in lung cancer has not yet been elucidated. In this study, we analyzed P3H3 expression in a panel of lung cancer cell lines and primary lung tumors. Epigenetic regulation was explored and the function of P3H3 was investigated by stable transfection and RNA interference. We found that P3H3 was downregulated in 6 out of 10 lung cancer cell lines. A heterogeneous methylation pattern of P3H3 was found in the exon region. In primary lung tumors, immunohistochemistry on tissue microarray (TMA) showed that higher expression of P3H3 was significantly associated with lower tumor N stage and grade (p = 0.035 and p = 0.026, respectively). Ectopic expression of P3H3 inhibited cell proliferation, colony formation, migration as well as invasion, and induced apoptosis together with cell cycle arrest in the G2/M phase. Knockdown of P3H3 led to increased migratory and invasive potential. These Phenomena are accompanied by enhanced p21, decreased cyclin A1 levels and increased caspase 3/7 activities. Taken together, we feel that P3H3 is a novel tumor suppressor and its protein expression is inversely related to lymph node metastasis and tumor differentiation in lung cancer.

Turning the gun on cancer: Utilizing lysosomal P-glycoprotein as a new strategy to overcome multi-drug resistance

Oxidative stress plays a role in the development of drug resistance in cancer cells. Cancer cells must constantly and rapidly adapt to changes in the tumor microenvironment, due to alterations in the availability of nutrients, such as glucose, oxygen and key transition metals (e.g., iron and copper). This nutrient flux is typically a consequence of rapid growth, poor vascularization and necrosis. It has been demonstrated that stress factors, such as hypoxia and glucose deprivation up-regulate master transcription factors, namely hypoxia inducible factor-1α (HIF-1α), which transcriptionally regulate the multi-drug resistance (MDR), transmembrane drug efflux transporter, P-glycoprotein (Pgp). Interestingly, in addition to the established role of plasma membrane Pgp in MDR, a new paradigm of intracellular resistance has emerged that is premised on the ability of lysosomal Pgp to transport cytotoxic agents into this organelle. This mechanism is enabled by the topological inversion of Pgp via endocytosis resulting in the transporter actively pumping agents into the lysosome. In this way, classical Pgp substrates, such as doxorubicin (DOX), can be actively transported into this organelle. Within the lysosome, DOX becomes protonated upon acidification of the lysosomal lumen, causing its accumulation. This mechanism efficiently traps DOX, preventing its cytotoxic interaction with nuclear DNA. This review discusses these effects and highlights a novel mechanism by which redox-active and protonatable Pgp substrates can utilize lysosomal Pgp to gain access to this compartment, resulting in catastrophic lysosomal membrane permeabilization and cell death. Hence, a key MDR mechanism that utilizes Pgp (the "gun") to sequester protonatable drug substrates safely within lysosomes can be "turned on" MDR cancer cells to destroy them from within.

Decalepis hamiltonii inhibits tumor progression and metastasis by regulating the inflammatory mediators and nuclear factor κB subunits

Metastasis is an extremely complex process that is a major problem in the management of cancer. In the present study, we had evaluated the antimetastatic activity of DECALEPIS HAMILTONI: using B16F-10 melanoma-induced experimental lung metastasis in a C57BL/6 mice model.

D HAMILTONI

treatment significantly ( : < .01) inhibited lung tumor nodule formation and reduced the lung collagen hydroxyproline, hexosamine, and uronic acid levels. Similarly serum sialic acid and γ-glutamyl transpeptidase levels were also significantly inhibited after

D HAMILTONI

treatment. The levels of proinflammatory cytokines such as tumor necrosis factor α, interleukin (IL)-1β, IL-6, granulocyte monocyte colony-stimulating factor, and IL-2 in the serum of these animals were significantly altered after

D HAMILTONI

treatment. The serum NO level was also found to be significantly decreased after

D HAMILTONI

treatment. This decreased NO level after

D HAMILTONI

treatment was also accompanied by decreased inducible NO synthase and cyclooxygenase-2 expression. The study reveals that

D HAMILTONI

treatment could alter proinflammatory cytokine production and could inhibit the activation and nuclear translocation of p65 and p50 subunits of nuclear factor κB in B16F-10 cells.