In part due to sex-dependent factors (including the X-chromosome and female sex hormone levels). However, recent studies have suggested that inclusion of both sexes in our studies is necessary to identify potential molecular mechanisms. Therefore, most studies using male rats are limited in the scope with respect to our overall understanding of the development and progression of certain cancers in humans.

In part due to sex-dependent factors (including the X-chromosome and female sex hormone levels). However, recent studies have suggested that inclusion of both sexes in our studies is necessary to identify potential molecular mechanisms. Therefore, most studies using male rats are limited in the scope with respect to our overall understanding of the development and progression of certain cancers in humans.

Honestly, most people use male rats because they do not want to deal with hormones in female rats (but the same also applies to mice). However, there are sex-dependent differences in drug metabolism and liver enzymes, thus it should be imperative to include both male and female rats. There also is a cost issue associated with these studies, and that is ultimately why people work with one sex.  The other caveat is if it is a breast or ovarian cancer study, it should be done in female rodents.

We can make a choice between male and female mice on the bases of statistics of cancer. For a long duration experiments female mice are better; as male mice gnaw more on tumor sites and cause increase in inflammation and this can affect the results. Moreover female mice with tumor can housed together in a cage (depends upon cage size) while the male mice are more aggressive especially when they get tumor and there are more chances of unwanted injuries. Hormonal levels can affect the results in both cases (male/female). 

In general we prefer female mice for cancer xenograft to avoid dominance phenomena although it depends on the type of cancer that you want to study e.g if i want to study prostate cancer i must use male not female mice. Several diseases are sex dependent or some kind of cancer that have an incidence higher in female respect to male. I attach an paper that explain different pathways in male and female upon stress activation. 

It does not matter what gender mice/rat you use, however, that depends on the type of cancer you are working.  In some cases if you have cell lines modified with ER construct to induce the gene expression then one will have to use male rat or mice.  Otherwise it is your choice of animals to use.

It depends on what you are looking for. We were working with immunotherapy and found that in general the tumour growth rate was higher in male than in female mice, as the anti-tumour immune response of the females seemed more efficient. 

Thanks a lot Kunnimalaiyaan and Martinez for your answer, specifically we would like to induce lung cancer by benzo(a)pyrene (single IP injection) in female rats. What would you like to suggest in our case.

that depends on the type of cancer you are working on it but to ovoid the female sex hormones

It depends on the type of cancer 

Honestly, depending on cancer type.

Recently, NIH mandates, animal expts should be carried out in both male and female mice.  However, some cancer types requires either male or female mice such prostate cancer, breast cancer respectively.

We are work on glioblastoma and many resercher suggested for female mouse model is the best option for the cancer type. However I couldn t understand what prominince of gender is.

To avoid the interference of the hormonal disturbances/changes.