Cell structure and function and response to chemotherapy in tumors heterotransplanted into the subrenal capsule of mice and rats

Detection and analysis of mammary gland stem cells

Emerging evidence from a variety of tissue types, including the mammary gland, suggests that normal stem and progenitor cells are the likely targets for malignant transformation, and that these transformed cells can function as cancer stem cells that drive tumour growth. In order to develop therapies that target these cancer stem cells, it is essential to determine the molecular mechanisms that regulate the growth and differentiation of these cells and their normal counterparts. To this end, a number of quantitative robust clonal assays have been developed that can detect the presence of human and mouse mammary stem and progenitor cells. These assays, when used in conjunction with cell-sorting strategies, have permitted the prospective isolation and characterization of a variety of cell types, including stem cells. Evidence to date indicates that these stem cells exhibit properties of basal mammary cells, possess extensive self-renewal properties, and are capable of generating a large number of phenotypically-distinct progenitor cells, many of which display characteristics of luminal cells. This review article will focus on the assays used to detect mammary stem and progenitor cells, some of the properties of these cells and their progeny and how they relate to the cancer stem cells that drive breast tumour growth.

Effects of chemotherapy on ultrastructure of oesophageal adenocarcinoma

AIMS

To compare and contrast the ultrastructural appearance of resected oesophageal adenocarcinomas treated with preoperative chemotherapy with that of non-treated resected controls; and to determine the usefulness of this method in the assessment of the effectiveness of the chemotherapeutic regimen.

METHODS

Ten resected oesophageal adenocarcinomas treated with preoperative chemotherapy--mitomycin-C, ifosfamide, and cisplatin (MIC)--were examined by transmission electron microscopy and their appearance compared with that of 13 concurrent untreated resected oesophageal adenocarcinomas.

RESULTS

The treated adenocarcinomas showed cytotoxic damage although complete tumour eradication was not achieved. In all 10 treated cases a variable proportion of the neoplastic cells showed unusual degenerative and necrotic changes not seen in untreated cases. In the most affected carcinomas the stroma contained increased numbers of inflammatory cells.

CONCLUSIONS

This ultrastructural method is useful for the assessment of the in vivo effect of MIC.

Morphological heterogeneity and phenotypical instability versus metastatic stability in the murine tumor model ER 15-P

At clinical presentation, the majority of malignant tumors are composed of multiple clonal subpopulations of tumor cells with different phenotypic characteristics. Using the experimental tumor model ER 15-P, a methylcholanthrene-induced pleomorphic sarcoma of the C57 Bl6J mouse, we studied a system of long-term in vivo passages of this primary tumor for cell morphological changes, and alterations in the potential for spontaneous lung metastases. Transplants from the primary after the 4th, 20th, 40th and 80th i.m. passage (referred to as T4, T20, T40, and T80 respectively) together with their lung metastases were investigated by light microscopy, immunohistochemistry, and electron microscopy. In addition, the potential for metastasis to the lungs in each group was determined and compared with that of the parent T4 tumors. T4 tumors were mainly composed of spindle-shaped tumor cells with the ultrastructural features of fibroblasts and myofibroblasts, often arranged in a storiform or fasciculated growth pattern, and intermingled with tumor giant cells. Some small areas contained polygonal or rounded tumor cells, ultrastructurally undifferentiated, and sometimes arranged in a hemangiopericytoma-like growth pattern. Although electron-microscopical findings clearly demonstrated the mesenchymal origin of these tumor cells, immunostaining with a polyclonal antibody to vimentin was unspecific in all tumor cells and normal mouse tissue. Monoclonal antibodies to vimentin from different sources were completely negative in tumor cells and murine stromal components. In contrast, myofibroblast-like tumor cells showed immunohistochemically, a moderate to strong co-expression with monoclonal antibodies to desmin, muscle actin and alpha-smooth muscle actin. On the basis of these morphological findings, the primary ER 15-P was classified as a pleomorphic myofibrosarcoma. The lung metastases of T4 tumors were mainly composed of undifferentiated round to polygonal tumor cells, while the number of desmin-positive, muscle- and alpha-smooth muscle-actin-positive cells was reduced. The morphological features of T20 tumors and their lung metastases were the same as in T4, indicating a relative stability of the phenotype up to that stage. In contrast, T40 and T80 tumors and their lung metastases were found to contain almost exclusively undifferentiated tumor cells and many tumor giant cells. While fibroblast-like tumor cells were seen only occasionally, myofibroblast-like tumor cells had almost completely disappeared. The potential for lung metastases was nearly constant in all groups, suggesting metastatic stability. Obviously, the undifferentiated tumor cells of this model are associated with a higher metastatic potential.

Instability of xenotransplanted soft tissue sarcomas. Morphologic and flow cytometric results

Human tumors transplanted into nude mice are widely considered to be identical to the tumor of origin. In addition, high histologic constancy of xenografts over many passages is generally accepted. We have checked these prerequisites for a therapy-orientated application of the nude mouse model using soft tissue sarcomas. Twenty-two primary soft tissue sarcomas and their xenografts were compared histologically and flow cytometrically over numerous passages. More than 30% of transplants showed a variation in cell differentiation, cell content, frequency of mitosis, tendency to necrotize, and connective tissue content compared to the original tumor. Furthermore, transplants from various regions in one tumor showed divergent results. Analyses of serial transplants showed histologic and flow cytometrical discrepancies in about 50% of cases, and new cell lines occurred in 26%. Our results show that the genetic instability found in human neoplasias also applies to xenotransplants and that the therapy-related usefulness of the nude mouse model is limited.

Subrenal capsule assay for fresh human tumors in immunocompetent mice; an inappropriate technique for non-small cell lung cancer

The subrenal capsule assay (SRA) seems to present some difficulties for the evaluation of the chemosensitivity of antineoplastic agents against fresh tumor xenografts. A study was therefore carried out to verify whether two different xenografts would behave in a similar way. Tumors such as melanoma provided adequate homogeneous material for this technique, while non-small cell lung carcinoma (NSCLC) were heterogeneous since the 1 mm3 specimen grafted under the renal capsule usually contained diffuse areas of necrosis and of infection. Furthermore, a large proportion of the grafted specimens, 257 out of 298, did not contain any tumor at all on microscopic examination even when they showed macroscopic growth. Added to these discrepancies, a random microscopic analysis of 180 adjacent fragments of NSCLC and melanomas demonstrated that the variability of heterogeneous tumors precludes any meaningful comparison between homologous tumor tissues designed to be grafted on treated and on control mice. The anti-inflammatory effect of chemotherapeutic drugs on the host's reaction to the graft is probably responsible for the differences between the macroscopic growth results observed in pieces grafted to both treated and control mice: however, it could not be simulated by hydrocortisone (HC) under our experimental conditions. This allows us to conclude that fresh tumors from NSCLC cannot be used in SRA.