My suggestion is to e-mail ATCC customer service and ask them if they know. I looked at some papers from 1952 and 1955 and they only mention that they were derived from a C57BL mouse in 1951 but don't give any mention of the sex.
Thank you both for your replies. I have now found, with the help of ATCC, that the cell line is derived from a male C57BL mouse. Please see p39 of the manuscript by Sugiura and Stock, (The effect of phosphoramides on the growth of a variety of mouse and rat tumors", Cancer Res, 1955; 15:38-51) for reference.
Marie, you mean the bladder or the lung carcinoma? The reference you have listed says that the bladder carcinoma was derived from the male but does not give the sex for the lung carcinoma. The references for the lung are not available online.