Table 3.

TROUBLESHOOTING

Step	Problem	Possible Reason	Solution
1–16	Wounds noted on dorsal skin	Mice are fighting	Separate the aggressor, individually house all males and aggressive females; Interpret results with caution since wounding promotes tumor development
13–16	Weight loss	Toxicity associated with chemotherapeutic or chemopreventive agent	Lower the dose of chemopreventive or chemotherapeutic agent; Interpret results with caution since negative energy balance inhibits tumor response
		Lack of food consumption; Dietary delivery of chemotherapeutic or chemopreventive agent has made chow less palatable	Change route of delivery; Interpret results with caution since negative energy balance inhibits tumor response
		Cachexia due to large tumor burden or malignant progression	Sacrifice individual mice and harvest tissue; terminate the experiment if indicated by IACUC regulations. Note: Papilloma counts may be unreliable after the appearance of SCC.
			In subsequent experiments reduce the dose of DMBA and/or TPA
12–16	No tumors arise in positive control group	Resistant strain was used as a positive control; Dose of initiating or promoting agent too low	Use a sensitive strain, backcross transgene or gene deficiency allele to sensitive strain such as FVB. Increase the doses of DMBA/TPA.
		Improper composition, storage, or handling of DMBA or TPA solutions	Verify solution composition; Prepare a fresh stock of DMBA for each initiation and protect from light; Store TPA solutions at −20°C.
12–16	Predicted effect of therapeutic or preventative agent or genetic manipulation is not detected	True negative result	Do nothing
		False negative results may occur if the doses of DMBA/TPA overwhelm the potential preventative or therapeutic effect of treatment or genetic manipulation	Lower the dose of DMBA/TPA
		Inadequate statistical power	Recalculate the necessary sample size based upon newly collected preliminary data
12–16	Abnormal lesions form	Transgene or inhibitor conferred unexpected gross appearance of papillomas	Harvest tumors tissues, cut sections and perform histologic investigation.
12–16	Papillomas arise but a portion regresses	Tumor regression is normal and the rate at which it occurs depends upon the strain utilized	Adjust tumor incidence and multiplicity calculations as necessary