Methods for evaluating the morphological and immunohistochemical properties of human tumor colonies grown in soft agar

Patient-derived xenografts, the cancer stem cell paradigm, and cancer pathobiology in the 21st century

Cancer is a heterogeneous disease manifest in many forms. Tumor histopathology can differ significantly among patients and cellular heterogeneity within tumors is common. A primary goal of cancer biologists is to better understand tumorigenesis and cancer progression; however, the complex nature of tumors has posed a substantial challenge to unlocking cancer's secrets. The cancer stem cell (CSC) paradigm for the pathobiology of solid tumors appropriately acknowledges phenotypic and functional tumor cell heterogeneity observed in solid tumors and accounts for the disconnect between drug approval based on response and the general inability of approved therapies to meaningfully impact survival due to their failure to eradicate these most important of cellular targets. First proposed to exist decades ago, CSC have only recently begun to be precisely identified due to technical advancements that facilitate identification, isolation, and interrogation of distinct tumor cell subpopulations with differing ability to form and perpetuate tumors. Precise identification of CSC populations and the complete hierarchy of cells within solid tumors will facilitate more accurate characterization of patient subtypes and ultimately contribute to more personalized and effective therapies. Rapid advancement in the understanding of tumor biology as it exists in patients requires cooperation among institutions, surgeons, pathologists, cancer biologists and patients alike, primarily because this translational research is best done with patient-derived tissue grown in the xenograft setting as patient-derived xenografts. This review calls for a broader change in the approaches taken to study cancer pathobiology, highlights what implications the CSC paradigm has for pathologists and cancer biologists alike, and calls for greater collaboration between institutions, physicians and scientists in order to more rapidly advance our collective understanding of cancer.

The human tumour cloning assay in the management of breast cancer patients

A tumour cloning system was used to cultivate breast cancer specimens. Fifty-six percent of 87 samples were adequate for evaluation, showing clonal growth in about one third (35%). Effusions yielded significantly better growth than solid specimens, the median colony numbers being 64 and 18 respectively. An attempt was made to examine whether there was any association between parameters accepted as prognostic factors for breast cancer and clonal growth in vitro. No correlation was found between preoperative tumour burden, histopathologic grading, menopausal status or overall survival and clonal growth in vitro, whereas we observed an inverse trend between progesterone receptor content of the tumours and their growth potential (P less than 0.01). In those few cases where in vitro and in vivo data could be compared, a high accuracy of the predicted sensitivities was found with respect to chemotherapy, but not in relation to hormonal treatment. A statistically significant higher overall chemosensitivity was associated with the absence of oestrogen receptors (P less than 0.01).

Diagnostic electron microscopy for amelanotic melanoma: correlation of patient biopsy, soft agar assay, and xenograft

In an attempt to diagnose a suspected amelanotic melanoma tumour, we examined a variety of tissue and cell samples from one patient at the ultrastructural level, which consisted of single cell suspensions of tumour cells with and without DOPA treatment, tumour cells after culture in agar with and without DOPA treatment, and single tumour cells hetero-transplanted into a nude mouse. Premalanosomes were not observed in sections of the amelanotic tumour with routine electron microscopy. Osmophilic-dense bodies, suggestive of melanosomes, were noted in the single cells in suspension treated with DOPA and cells grown in agar without DOPA treatment. Definitive premelanosomes, with an identifiable striated matrix, were only observed in cells grown into colonies in agar and treated with DOPA. Positive L-DOPA reaction products were noted in the golgi complex, endoplasmic reticulum closely related to the golgi (GERL), and in vacuoles from cells grown in agar. As controls, Cloudman S91 53.1 melanoma cells were evaluated as single cells in suspension or as colonies after culture in agar, both with and without DOPA treatment. Premelanosomes were always observed in this established melanoma cell line while DOPA-treated cells contained positive L-DOPA reaction products. The overall findings identified the tumour as amelanotic melanoma and indicated that both DOPA treatment and culture in agar were needed for the demonstration of premelanosomes.

Tissue-specificity of reactivity to concanavalin-A of human cells in culture

Concanavalin-A (Con-A) reactivity was studied to identify the tissue-specificity of cells established from various normal human tissues. Cells were treated with Con-A-labelled human red blood cells (C-RBC). C-RBC was not absorbed on the cells derived from the bone marrow, skin and liver. Lung-derived fibroblast cells showed weak C-RBC adsorption. Kidney-derived cells showed epithelial morphology and easily adsorbed C-RBC. These suggest that a large number of Con-A receptors exists on the membrane surface of kidney cells.