Progressive tumor growth-associated altered tumor microenvironment: implications in a tumor stage-dependent modulation in survival of a murine T cell lymphoma. 
In the present study using a transplantable murine T cell lymphoma designated as Dalton's lymphoma, we investigated the role of oxygen, glucose and other environmental factors in evolution of altered survival responses in tumor cells during the late tumor-bearing stages.  Tumor progression was observed to be associated with an improvement in the survival ability of tumor cells.  Moreover, tumor serum and ascitic fluid obtained from the late tumor bearing stage was found to augment tumor cell survival in vitro, indicating that these humoral components of tumor bearing host contain factors capable of modulating tumor survival.  Progressive tumor growth was also shown to be associated with depletion in glucose and oxygen content in the fluids of tumor microenvironment along with a concomitant augmentation in the production of lactate and lactate dehydrogenase.  Moreover, tumor cells expressed higher amount of mRNA for inducible nitric oxide synthase, Hypoxia inducible factor-1 and 2 and Hsp70 and VEGF proteins during the late tumor bearing stages.  Splenic macrophages and non-adherent splenic lymphocytes from tumor-bearing mice showed an increased production of IL-6, TGF-beta, IFN-gamma, IL-2R and VEGF during the late tumor-bearing stage, which could be implicated in the differential regulation of tumor growth in a tumor stage dependent manner.  In conclusion, the observations of the present study suggest that factors contained in altered tumor microenvironment may act in concert to cause behavioral alterations in tumor cells, with respect to survival, during the course of the progression of a nonsolid T cell lymphoma.