Clonogenic assay of gastric adenocarcinoma stem cells--clonogenic assay, stomach cancer

Abstract

Clonogenic assay is the culturing of tumor stem cells, which are responsible for tumor growth by self renewal and differentiation to tumor end cells. Elimination of the malignant stem cells or their self renewal will lead cure of the tumor. Thus, the behavior of the stem cells by clonogenic assay has been correlated with prognosis and outcome of therapy.

We studied clonogenic assay by means of double agar system for 21 patients with advanced stomach cancer. The colony formation evaluted on 14th day of the culture was grown from 14 of 19 malignant effusions plated and 1 of 2 tumor nodules plated. The number of the colonies ranged from 5 to 96 per petri dish, and the median number was 20. The plating efficiency ranged from 0.001 to 0.036%, and the median was 0.003%. In the morphologic studies, the colonies made of tightly packed cells were grown from the poorly differentiated adenocarcinoma, whereas the colonies made of loosely packed cells with mucin formation were grown from the mucin secreting adenocarcinoma of stomach. The chemosensitivity in vitro tests to cisplatin were performed in 5 patients, and the results showed 4 sensitive and 1 resistant patient. The result of in vivo study with instillation of intraperitoneal cisplatin revealed that 3 patients “in vitro sensitive” were “responsive in vivo”, and 1 patient “in vitro resistant” was “non-responsive in vivo”.

We conclude that clonogenic assay of stomach cancer is useful method to understand the biology of the stem cell pool and select proper chemotherapy according to the chemosensitivity test.

Fig. 1.

In vitro chemosensitivity of case No. 2 and No. 5 to cisplatin (●) and case No. 9 to 5-fluorouracil (○).

Fig. 2.

A. Poorly differentiated adenocarcinoma. a. Original histology, HE stain ×400. b. Colony characterized by numerous tightly packed cells ×400. c. Papanicolaou stain of colony after permanent fixation ×400. B. Mucin secreting adenocarcinoma. a. Original histology, HE stain ×400. b. Colony made of loosly packed cells with mucin formation ×200. c. Papanicolaou stain of the colony ×400.